EXHIBIT 4.2

                      CONVERTIBLE SUBORDINATED DEBENTURE

                              PURCHASE AGREEMENT

     CONVERTIBLE SUBORDINATED DEBENTURE PURCHASE AGREEMENT ("Agreement") 
dated as of February 2, 1999 between ZITEL CORPORATION, a California 
corporation (the "Company"), and each person or entity listed as an investor 
on Schedule I attached to this Agreement (each individually an "Investor" and 
collectively the "Investors").

                                  WITNESSETH

     WHEREAS, the Company desires to sell and issue to the Investors, and the 
Investors wish to purchase from the Company, 3% Convertible Subordinated 
Debentures due February 1, 2000 (the "Debentures"), in the aggregate 
principal amount of $5,000,000 at an aggregate price of $5,000,000, having 
the rights and privileges set forth in the Debentures in the form of EXHIBIT 
1.1A attached hereto (the "Issuance"), on the terms and conditions set forth 
herein; and

     WHEREAS, the Debentures will be convertible into shares ("COMMON 
SHARES") of common stock, no par value of the Company ("COMMON STOCK"), 
pursuant to the terms of the Debentures, and the Investors will have 
registration rights with respect to such Common Shares and the Warrant Shares 
(as defined herein), pursuant to the terms of that certain Registration 
Rights Agreement to be entered into between the Company and the Investors 
substantially in the form of EXHIBIT 4.2(f) hereto ("REGISTRATION RIGHTS 
AGREEMENT"); and

     WHEREAS, to induce the Investors to purchase the Debentures, the Company 
has agreed to issue to the Investors warrants exercisable for 75,000 shares 
of Common Stock, in the form attached as EXHIBIT 1.1B (the "WARRANTS");

     NOW, THEREFORE, in consideration of the foregoing premises and the 
covenants contained herein and other good and valuable consideration, the 
receipt and sufficiency of which are hereby acknowledged, the parties hereto 
agree as follows:

                                   ARTICLE 1

                 PURCHASE AND SALE OF DEBENTURES AND WARRANTS

     1.1  ISSUANCE OF DEBENTURES AND WARRANTS.  Upon the following terms and 
conditions, the Company shall issue and sell to each Investor severally, and 
each Investor severally shall purchase from the Company, the outstanding 
principal amount of Debentures indicated next to such Investor's name on 
Schedule I attached hereto.

          (a)  ISSUANCE.  Upon the following terms and conditions, the 
Company shall issue and sell to each Investor severally, and each Investor 
severally shall purchase from the 


                                      1


Company, the principal amount of Debentures and the number of Warrants 
indicated next to such Investor's name on SCHEDULE I attached hereto.

          (b)  PURCHASE PRICE.  The purchase price for the Debentures to be 
acquired by each Investor (the "PURCHASE PRICE") shall be the Purchase Price 
set forth next to such Investor's name on SCHEDULE I.

          (c)  THE CLOSING.

               (i)   The closing of the purchase and sale of the Debentures 
and the Warrants (the "Closing"), shall take place at 10:00 am., local time 
on the later of the following:  (x) February 2, 1999, (y) the date on which 
the last to be fulfilled or waived of the conditions set forth in Article IV 
hereof and applicable to the Closing shall be fulfilled or waived in 
accordance herewith, or (z) such other time and place and/or on such other 
date as the Investors and the Company may agree.  The date on which the 
Closing occurs is referred to herein as the "Closing Date".

               (ii)  On the Closing Date, the Company shall deliver to each 
Investor (x) certificates (with the number of and outstanding principal 
amount of such certificates requested by such Investor) representing the 
Debentures purchased hereunder by such Investor at the Closing registered in 
the name of such Investor or its nominee and (y) the Warrants registered in 
the name of Investor or its nominee in such denominations as reasonably 
requested by such Investor, and such Investor shall deliver to the Company 
the Purchase Price for the Debentures purchased by such Investor hereunder by 
wire transfer in immediately available funds to an account designated in 
writing by the Company. The delivery of payment by each Investor of the 
Purchase Price applicable to it as set forth in this paragraph shall 
constitute a payment delivered to the Company in satisfaction of such 
Investor's obligation to pay the Purchase Price hereunder.  In addition, each 
party shall deliver all documents, instruments and writings required to be 
delivered by such party pursuant to this Agreement at or prior to the 
applicable Closing.  Notwithstanding anything to the contrary herein, the 
Closing may be conducted through LaSalle National Bank, 135 South LaSalle 
Street, Chicago, Illinois 60603 (the "Escrow Agent") as set forth in that 
certain escrow agreement dated as of January 27, 1999 among the Company, the 
Escrow Agent and Rochon Capital Group, Ltd.

                                   ARTICLE 2

                        REPRESENTATIONS AND WARRANTIES

     2.1  REPRESENTATIONS AND WARRANTIES OF THE COMPANY.  The Company hereby 
makes the following representations and warranties to each of the Investors 
as of the date hereof and on each Closing Date:

          (a)  ORGANIZATION AND QUALIFICATION; MATERIAL ADVERSE EFFECT.  The 
Company is a corporation duly incorporated and existing in good standing 
under the laws of the State of California and has the requisite corporate 
power to own its properties and to carry on its business as now being 
conducted.  The Company does not have any direct or indirect subsidiaries 
other than the subsidiaries listed in Section 2.1(a) of the Company's 
disclosure 


                                      2


schedule delivered to the Investors and attached hereto (the "Disclosure 
Schedule").  Except where specifically indicated to the contrary, all 
references in this Agreement to subsidiaries shall be deemed to refer to all 
direct and indirect subsidiaries of the Company.  The Company is duly 
qualified as a foreign corporation to do business and is in good standing in 
every jurisdiction in which the nature of the business conducted or property 
owned by it makes such qualification necessary other than those in which the 
failure so to qualify would not have a Material Adverse Effect.  "MATERIAL 
ADVERSE EFFECT" means any adverse effect on the business, operations, 
properties, prospects, or financial condition of the entity with respect to 
which such term is used and which is (either alone or together with all other 
adverse effects) material to such entity and other entities controlling or 
controlled by such entity taken as a whole, and any material adverse effect 
on the transactions contemplated under this Agreement, the Registration 
Rights Agreement or any other agreement or document contemplated hereby or 
thereby.

          (b)  AUTHORIZATION; ENFORCEMENT.  (i) The Company has all requisite 
corporate power and authority to enter into and perform this Agreement, the 
Warrants and the Registration Rights Agreement and to issue the Debentures 
and Warrants in accordance with the terms hereof and thereof, (ii) the 
execution and delivery of this Agreement, the Warrants and the Registration 
Rights Agreement by the Company and the consummation by it of the 
transactions contemplated hereby and thereby, including the issuance of the 
Debentures, the Common Shares and the Warrant Shares have been duly 
authorized by all necessary corporate action, and no further consent or 
authorization of the Company or its Board of Directors (or any committee or 
subcommittee thereof) or stockholders is required, (iii) this Agreement, the 
Warrants, the Debentures and the Registration Rights Agreement have been duly 
executed and delivered by the Company, and (iv) this Agreement, the Warrants, 
the Debentures and the Registration Rights Agreement constitute valid and 
binding obligations of the Company enforceable against the Company in 
accordance with their terms, except as such enforceability may be limited by 
applicable bankruptcy, insolvency, reorganization, moratorium, liquidation or 
similar laws relating to, or affecting generally the enforcement of 
creditors' rights and remedies or by other equitable principles of general 
application.

          (c)  CAPITALIZATION.  As of January 15, 1999, the authorized 
capital stock of the Company consisted of 40,000,000 shares of Common Stock 
and 1,000,000 shares of preferred stock; there are 21,907,553 shares of 
Common Stock and no shares of preferred stock issued and outstanding; and 
3,402,031 shares of Common Stock and no shares of preferred stock are 
reserved for issuance to persons other than the Investors.  After the 
Closing, 3,402,031 shares of Common Stock and no shares of preferred stock 
will be reserved for issuance to persons other than the Investors.  All of 
the outstanding shares of the Company's Common Stock and preferred stock have 
been validly issued and are fully paid and nonassessable.  No shares of 
capital stock are entitled to preemptive rights; and there are as of the date 
hereof outstanding options for 1,861,551 shares of Common Stock and 150,000 
outstanding warrants for shares of Common Stock (excluding the Warrants).  
Except as set forth in Section 2.1(c) of the Disclosure Schedule, there are 
no other scrip, rights to subscribe to, calls or commitments of any character 
whatsoever relating to, or securities or rights exchangeable for or 
convertible into, any shares of capital stock of the Company, or contracts, 
commitments, understandings, or arrangements by which the Company is or may 
become bound to issue additional shares of capital stock of the Company or 
options, warrants, scrip, rights to subscribe to, or commitments to purchase 
or acquire, any shares, or securities or rights convertible or exchangeable 
into shares, of capital stock of the 


                                      3


Company.  Attached hereto as EXHIBIT 2.1(c)(i) is a true and correct copy of 
the Company's Articles of Incorporation (the "CHARTER"), as in effect on the 
date hereof, and attached hereto as EXHIBIT 2.1(c)(ii) is a true and correct 
copy of the Company's By-Laws, as in effect on the date hereof (the 
"BY-LAWS").

          (d)  ISSUANCE OF COMMON SHARES.  The Common Shares and the shares 
of Common Stock issuable upon the exercise of the Warrants (the "WARRANT 
SHARES") are duly authorized and reserved for issuance and, upon such 
conversion in accordance with the Debentures and/or exercise in accordance 
with the Warrants such Common Shares and Warrant Shares will be validly 
issued, fully paid and non-assessable, free and clear of any and all liens, 
claims and encumbrances, and entitled to be traded on the Nasdaq National 
Market System ("NASDAQ NMS") (or the American Stock Exchange or the New York 
Stock Exchange, collectively with the Nasdaq NMS, the "APPROVED MARKETS"), 
and the holders of such Common Shares and Warrant Shares shall be entitled to 
all rights and preferences accorded to a holder of Common Stock.  The 
outstanding shares of Common Stock are currently listed on the Nasdaq NMS.

          (e)  NO CONFLICTS.  The execution, delivery and performance of this 
Agreement, the Registration Rights Agreement and the Warrants by the Company 
and the consummation by the Company of the transactions contemplated hereby 
and thereby and the issuance of the Debentures and the Warrants do not and 
will not (i) result in a violation of the Company's Charter or By-Laws or 
(ii) conflict with, or constitute a default (or an event which with notice or 
lapse of time or both would become a default) under, or give to others any 
rights of termination, amendment, acceleration or cancellation of, any 
agreement, indenture, patent, patent license or instrument to which the 
Company or any of its subsidiaries is a party, or (iii) result in a violation 
of any federal, state, local or foreign law, rule, regulation, order, 
judgment or decree (including Federal and state securities laws and 
regulations) applicable to the Company or any of its subsidiaries or by which 
any property or asset of the Company or any of its subsidiaries is bound or 
affected.  The business of the Company and its direct and indirect 
subsidiaries is being conducted in material compliance with all applicable 
laws, ordinances or regulations of any governmental entity.  The Company is 
not required under Federal, state, local or foreign law, rule or regulation 
to obtain any consent, authorization or order of, or make any filing or 
registration with, any court or governmental agency in order for it to 
execute, deliver or perform any of its obligations under this Agreement, the 
Registration Rights Agreement, the Debentures and the Warrants or issue and 
sell the Debentures in accordance with the terms hereof and issue the Common 
Shares upon conversion thereof and issue the Warrant Shares on exercise of 
the Warrants and for the registration provisions provided in the Registration 
Rights Agreement, except as specified herein and in the Registration Rights 
Agreement and the Warrant.

          (f)  SEC DOCUMENTS; NO NON-PUBLIC INFORMATION; FINANCIAL 
STATEMENTS. The Common Stock of the Company is registered pursuant to Section 
12(g) of the Securities Exchange Act of 1934, as amended (the "EXCHANGE ACT") 
and the Company has filed all reports, schedules, forms, statements and other 
documents required to be filed by it with the Securities and Exchange 
Commission ("SEC") pursuant to the reporting requirements of the Exchange 
Act, including material filed pursuant to Section 13(a) or 15(d), in addition 
to one or more registration statements and amendments thereto heretofore 
filed by the Company with the SEC 


                                      4


(all of the foregoing including filings incorporated by reference therein 
being referred to herein as the "SEC DOCUMENTS").  The Company has delivered 
or made available to the Investors true and complete copies of all SEC 
Documents (including, without limitation, proxy information and solicitation 
materials and registration statements) filed with the SEC since September 30, 
1998, all annual SEC Documents filed with the SEC since September 30, 1997, 
and all press releases issued by the Company since May 28, 1998 as set forth 
in Section 2.1(f) of the Disclosure Schedule (the "Press Releases").  The 
Company has not directly or indirectly provided to the Investor any 
information that currently constitutes material non-public information or any 
information which, according to applicable law, rule or regulation, should 
have been disclosed publicly by the Company but which has not been so 
disclosed.  As of their respective dates, the SEC Documents complied in all 
material respects with the requirements of the Exchange Act and the rules and 
regulations of the SEC promulgated thereunder and other federal, state and 
local laws, rules and regulations applicable to such SEC Documents, and none 
of the SEC Documents contained any untrue statement of a material fact or 
omitted to state a material fact required to be stated therein or necessary 
in order to make the statements therein, in light of the circumstances under 
which they were made, not misleading.  The SEC Documents and Press Releases 
contain all material information concerning the Company, and no event or 
circumstance has occurred which would require the Company to disclose such 
event or circumstance in order to make the statements in the SEC Documents 
and the Press Releases not misleading on the date hereof or on the Closing 
Date but which has not been so disclosed.  The financial statements of the 
Company included in the SEC Documents comply as to form and substance in all 
material respects with applicable accounting requirements and the published 
rules and regulations of the SEC or other applicable rules and regulations 
with respect thereto.  Such financial statements have been prepared in 
accordance with United States generally accepted accounting principles 
(except (i) as may be otherwise indicated in such financial statements or the 
notes thereto or (ii) in the case of unaudited interim statements, to the 
extent they may not include footnotes or may be condensed or summary 
statements) and fairly present in all material respects the financial 
position of the Company as of the dates thereof and the results of operations 
and cash flows for the periods then ended (subject, in the case of unaudited 
statements, to normal year-end audit adjustments).

          (g)  PRINCIPAL EXCHANGE/MARKET.  The principal market on which the 
Common Stock is currently traded is the Nasdaq NMS.

          (h)  NO MATERIAL ADVERSE CHANGE.  Since September 30, 1998, no 
Material Adverse Effect has occurred or exists, and no event or circumstance 
which has not been disclosed in the SEC Documents and Press Releases has 
occurred that with notice or the passage of time or both is reasonably likely 
to result in a Material Adverse Effect with respect to the Company or its 
subsidiaries.

          (i)  NO UNDISCLOSED LIABILITIES.  Except as disclosed in Section 
2.1(i) of the Company Disclosure Schedule, the Company and its subsidiaries 
have no liabilities or obligations not disclosed in the SEC Documents or the 
Press Releases, other than those liabilities incurred in the ordinary course 
of the Company's or its subsidiaries' respective businesses since September 
30, 1998, which liabilities, individually or in the aggregate, do not or 
would not have a Material Adverse Effect on the Company or its direct or 
indirect subsidiaries.


                                      5


          (j)  NO UNDISCLOSED EVENTS OR CIRCUMSTANCES.  No event or 
circumstance has occurred or exists with respect to the Company or its direct 
or indirect subsidiaries or their respective businesses, properties, 
prospects, operations or financial condition, which, under applicable law, 
rule or regulation, requires public disclosure or announcement by the Company 
but which has not been so publicly announced or disclosed.

          (k)  NO GENERAL SOLICITATION.  Neither the Company, nor any of its 
affiliates, or, to its knowledge, any person acting on its or their behalf 
has engaged in any form of general solicitation or general advertising 
(within the meaning of Regulation D under the Securities Act of 1933, as 
amended (the "Act")) in connection with the offer or sale of the Debentures 
or Common Shares.

          (l)  NO INTEGRATED OFFERING.  Neither the Company, nor any of its 
affiliates, nor to its knowledge any person acting on its or their behalf 
has, directly or indirectly, made any offers or sales of any security or 
solicited any offers to buy any security, under circumstances that would 
require registration of the Debentures, the Warrants or the Common Shares or 
Warrant Shares under the Act.  The issuance of the Debentures, Warrants, 
Common Shares, or Warrant Shares to the Investors will not be integrated with 
any other issuance of the Company's securities (past, current or future) 
which requires stockholder approval under the rules of the Nasdaq NMS.

          (m)  FORM S-3.  The Company is eligible to file a Registration 
Statement (as defined in the Registration Rights Agreement) on Form S-3 under 
the Act and rules promulgated thereunder for transactions involving secondary 
offerings, and Form S-3 is permitted to be used for the transactions 
contemplated by the Registration Rights Agreement involving secondary 
offerings under the Act and rules promulgated thereunder.

          (n)  INTELLECTUAL PROPERTY.  The Company (and/or its wholly-owned 
subsidiaries) owns or has licenses to use certain patents, copyrights and 
trademarks ("INTELLECTUAL PROPERTY") associated with its business.  The 
Company and its subsidiaries have all intellectual property rights which are 
material to the conduct of the business of the Company and its subsidiaries 
as it is now being conducted or as proposed to be conducted as disclosed in 
the SEC Documents.  The Company and its subsidiaries have no reason to 
believe that the intellectual property rights which it owns are invalid or 
unenforceable or that the use of such intellectual property by the Company or 
its subsidiaries infringes upon or conflicts with any right of any third 
party, and neither the Company nor any of its subsidiaries has received 
notice of any such infringement or conflict.  The Company and its 
subsidiaries have no knowledge of any material infringement of its 
intellectual property by any third party.

          (o)  SHAREHOLDER RIGHTS PLAN.  None of the acquisition of 
Debentures, Warrants, Common Shares or Warrant Shares nor the deemed 
beneficial ownership of shares of Common Stock prior to, or the acquisition 
of such shares pursuant to, the conversion of Debentures or the exercise of 
the Warrants will trigger the poison pill provisions of any stockholders' 
rights or similar agreements, or a substantially similar occurrence under any 
successor or similar plan.


                                      6


          (p)  NO LITIGATION.  Except as set forth in Section 2.1(p) of the 
Disclosure Schedule, no litigation or claim (including those for unpaid 
taxes) against the Company or any of its subsidiaries is pending or, to the 
Company's knowledge, threatened, and no other event has occurred, which if 
determined adversely could reasonably be expected to have a Material Adverse 
Effect on the Company or could reasonably be expected to materially and 
adversely effect the transactions contemplated hereby.  The legal proceedings 
described in the Disclosure Schedule will not have an effect on the 
transactions contemplated hereby, and will not have a Material Adverse Effect 
on the Company.

          (q)  BROKERS.  The Company has taken no action which would give 
rise to any claim by any person for brokerage commissions, finder's fees or 
similar payments by the Company or any Investor relating to this Agreement or 
the transactions contemplated hereby, except for amounts owing to Rochon 
Capital Group, Ltd. which amounts shall be paid exclusively by the Company, 
pursuant to a separate agreement.

          (r)  ACKNOWLEDGEMENT OF DILUTION.  The number of shares of Common 
Stock constituting Common Shares or Warrant Shares may increase substantially 
in certain circumstances, including the circumstance where the trading price 
of the Common Stock declines.  The Company acknowledges that its obligation 
to issue Common Shares upon conversion of Debentures and Warrant Shares upon 
exercise of the Warrants is absolute and unconditional (except as limited by 
NASD Rule 4460(i) and any similar rule of any other Approved Market on which 
the Common Stock may then be trading, Section 12 of the Debentures and 
Section 9 of the Warrants), regardless of the dilution that such issuance may 
have on other shareholders of the Company.

          (s)  OTHER INVESTORS.  Except as set forth in Section 2.1(s) of the 
Disclosure Schedule, there are no outstanding securities issued by the 
Company that are entitled to registration rights under the Act.  Except as 
set forth in SCHEDULE 2.1(s), there are no outstanding securities issued by 
the Company that are directly or indirectly convertible into, exercisable 
into, or exchangeable for, shares of Common Stock of the Company, that have 
anti-dilution or similar rights that would be affected by the issuance of the 
Debentures, the Common Shares, the Warrant Shares or the Warrants.

          (t)  CERTAIN TRANSACTIONS.  Except as disclosed in the SEC 
Documents and Section 2.1(t) of the Disclosure Schedule, none of the 
officers, directors, or employees of the Company is presently a party to any 
material transaction with the Company or any of its subsidiaries (other than 
for services as employees, officers and directors), including any contract, 
agreement or other arrangement providing for the furnishing of services to or 
by, providing for rental of real or personal property to or from, or 
otherwise requiring payments to or from any officer, director or such 
employee or, to the knowledge of the Company, any corporation, partnership, 
trust or other entity in which any officer, director, or any such employee 
has a substantial interest or is an officer, director, trustee or partner.

          (u)  PERMITS; COMPLIANCE.  The Company and each of its subsidiaries 
is in possession of all material franchises, grants, authorizations, 
licenses, permits, easements, variances, exemptions, consents, certificates, 
approvals and orders necessary to own, lease and operate its properties and 
to carry on its business as it is now being conducted (collectively, the 


                                      7


"COMPANY PERMITS"), and there is no action pending or, to the knowledge of 
the Company, threatened regarding suspension or cancellation of any of the 
Company Permits except for such Company Permits the failure of which to 
possess, or the cancellation or suspension of which, would not, individually 
or in the aggregate, have a material effect on the Company.  Neither the 
Company nor any of its subsidiaries is in material conflict with, or in 
material default or material violation of, any of the Company Permits.  Since 
September 30, 1998, neither the Company nor any of its subsidiaries has 
received any notification with respect to possible material conflicts, 
material defaults or material violations of applicable laws.

          (v)  INSURANCE.  The Company and each of its subsidiaries are 
insured by insurers of recognized financial responsibility against such 
losses and risks and in such amounts as management of the Company believes to 
be prudent and customary in the businesses in which the Company and its 
direct and indirect subsidiaries are engaged.  Neither the Company nor any 
such subsidiary has any reason to believe that it will not be able to renew 
its existing insurance coverage as and when such coverage expires or to 
obtain similar coverage from similar insurers as may be necessary to continue 
its business without a significant increase in cost.

          (w)  INTERNAL ACCOUNTING CONTROLS.  The Company and each of its 
subsidiaries maintain a system of internal accounting controls sufficient, in 
the judgment of the Company's board of directors, to provide reasonable 
assurance that (i) transactions are executed in accordance with management's 
general or specific authorizations, (ii) transactions are recorded as 
necessary to permit preparation of financial statements in conformity with 
generally accepted accounting principles and to maintain asset 
accountability, (iii) access to assets is permitted only in accordance with 
management's general or specific authorization and (iv) the recorded 
accountability for assets is compared with the existing assets at reasonable 
intervals and appropriate action is taken with respect to any differences.

          (x)  ENVIRONMENTAL MATTERS.  Except as otherwise disclosed in the 
SEC Documents, the Company and each of its subsidiaries is in compliance in 
all material respects with all applicable state and federal environmental 
laws and no event or condition has occurred that may interfere with the 
compliance by the Company or any of its subsidiaries with any environmental 
law or that may give rise to any liability under any environmental law that, 
individually or in the aggregate, would have a Material Adverse Effect.

          (y)  SOLVENCY.

               (i)   The Company's fair saleable value of its assets exceeds 
the amount that will be required to be paid on or in respect of the Company's 
existing debts and other liabilities (including contingent liabilities) as 
they mature.

               (ii)  The Company's assets do not constitute unreasonably 
small capital to carry out its business as now conducted and as proposed to 
be conducted including the Company's capital needs taking into account the 
particular capital requirements of the business conducted by the Company, and 
projected capital requirements and capital availability thereof.


                                      8


               (iii) The Company does not intend to incur debts beyond its 
ability to pay such debts as they mature (taking into account the timing and 
amounts of cash to be payable on or in respect of its debt).

               (iv)  The Company does not intend, and does not believe, that 
final judgments against the Company in actions for money damages will be 
rendered at a time when, or in an amount such that, the Company will be 
unable to satisfy any such judgments promptly in accordance with their terms 
(taking into account the maximum reasonable amount of such judgments in any 
such actions and the earliest reasonable time at which such judgments might 
be rendered.  The Company's cash flow, after taking into account all other 
anticipated uses of the cash (including the payments on or in respect of debt 
referred to in paragraph (iii) above), will at all times be sufficient to pay 
all such judgments promptly in accordance with their terms.

     Neither the Company nor any of its subsidiaries is subject to any 
bankruptcy, insolvency or similar proceeding.

          (z)  TAXES.  All federal, state, city and other tax returns, 
reports and declarations required to be filed by or on behalf of the Company 
have been filed and such returns are complete and accurate and disclose all 
taxes (whether based upon income, operations, purchases, sales, payroll, 
licenses, compensation, business, capital, properties or assets or otherwise) 
required to be paid in the periods covered thereby.  All taxes shown on such 
returns and any deficiency assessments, penalties and interest have been 
paid.  All taxes required to be withheld by or on behalf of the Company in 
connection with amounts paid or owing to any employees, independent 
contractor, creditor or other party have been withheld, and such withheld 
taxes have either been duly and timely paid to the proper governmental 
authorities or set aside in accounts for such purposes.

     2.2  REPRESENTATIONS AND WARRANTIES OF THE INVESTORS.  Each of the 
Investors, severally (as to itself) and not jointly, hereby makes the 
following representations and warranties to the Company as of the date hereof 
and on the Closing Date:

          (a)  AUTHORIZATION; ENFORCEMENT.  (i) Such Investor has the 
requisite power and authority to enter into and perform this Agreement and 
the Registration Rights Agreement and to purchase the Debentures being sold 
hereunder and to acquire the Warrant, (ii) the execution and delivery of this 
Agreement and the Registration Rights Agreement by such Investor and the 
consummation by it of the transactions contemplated hereby and thereby have 
been duly authorized by all necessary corporate or partnership action, and 
(iii) this Agreement and the Registration Rights Agreement constitute valid 
and binding obligations of such Investor enforceable against such Investor in 
accordance with their terms, except as such enforceability may be limited by 
applicable bankruptcy, insolvency, reorganization, moratorium, liquidation or 
similar laws relating to, or affecting generally the enforcement of 
creditors' rights and remedies or by other equitable principles of general 
application.

          (b)  NO CONFLICTS.  The execution, delivery and performance of this 
Agreement and the Registration Rights Agreement and the performance under the 
Debentures and Warrants and the consummation by such Investor of the 
transactions contemplated hereby and thereby do not and will not (i) result 
in a violation of such Investor's organizational documents, or (ii) 


                                      9


conflict with any agreement, indenture or instrument to which such Investor 
is a party, or (iii) result in a material violation of any law, rule, or 
regulation, or any order, judgment or decree of any court or governmental 
agency applicable to such Investor.  Such Investor is not required to obtain 
any consent or authorization of any governmental agency in order for it to 
perform its obligations under this Agreement, the Registration Rights 
Agreement, the Warrants or the Debentures.

          (c)  INVESTMENT REPRESENTATION.  Such Investor is purchasing the 
Debentures and the Warrants for its own account and not with a view to 
distribution in violation of any securities laws.  Such Investor has no 
present intention to sell the Debentures, Warrants, Common Shares, or Warrant 
Shares in violation of Federal or state securities laws and such Investor has 
no present arrangement (whether or not legally binding) to sell the 
Debentures, Warrants, Common Shares or Warrant Shares to or through any 
person or entity; provided, however, that by making the representations 
herein, such Investor does not agree to hold the Debentures, Warrants, Common 
Shares or Warrant Shares for any minimum or other specific term and reserves 
the right to dispose of the Debentures, Warrants, Common Shares or Warrant 
Shares at any time in accordance with Federal and state securities laws 
applicable to such disposition.

          (d)  ACCREDITED INVESTOR.  Such Investor is an "accredited 
investor" as defined in Rule 501 promulgated under the Act.  The Investor has 
such knowledge and experience in financial and business matters in general 
and investments in particular, so that such Investor is able to evaluate the 
merits and risks of an investment in the Debentures and to protect its own 
interests in connection with such investment.  In addition (but without 
limiting the effect of the Company's representations and warranties contained 
herein), such Investor has received such information as it considers 
necessary or appropriate for deciding whether to purchase the Debentures 
pursuant hereto.

          (e)  RULE 144.  Such Investor understands that there is no public 
trading market for the Debentures or Warrants, that none is expected to 
develop, and that the Debentures and Warrants and the Common Shares and 
Warrant Shares must be held indefinitely unless the Common Shares and Warrant 
Shares are registered under the Act or an exemption from registration is 
available.  Such Investor has been advised or is aware of the provisions of 
Rule 144 promulgated under the Act.

          (f)  BROKERS.  Such Investor has taken no action which would give 
rise to any claim by any person for brokerage commissions, finder's fees or 
similar payments by the Company relating to this Agreement or the 
transactions contemplated hereby, except for amounts owing to Rochon Capital 
Group, Ltd., which amounts will be paid exclusively by the Company, pursuant 
to a separate agreement.

          (g)  RELIANCE BY THE COMPANY.  Such Investor understands that the 
Debentures and Warrant are being offered and sold in reliance on a 
transactional exemption from the registration requirements of Federal and 
state securities laws and that the Company is relying upon the truth and 
accuracy of the representations, warranties, agreements, acknowledgments and 
understandings of such Investor set forth herein in order to determine the 
applicability of such exemptions and the suitability of such Investor to 
acquire the Debentures and Warrants.


                                      10


                                   ARTICLE 3

                                   COVENANTS

     3.1  REGISTRATION AND LISTING; EFFECTIVE REGISTRATION.  Until such time 
as no Debentures or Warrants are outstanding, the Company will cause the 
Common Stock to continue at all times to be registered under Section 12(g) of 
the Exchange Act, will comply in all respects with its reporting and filing 
obligations under the Exchange Act, and will not take any action or file any 
document (whether or not permitted by the Exchange Act or the rules 
thereunder) to terminate or suspend such reporting and filing obligations.  
Until such time as no Debentures or Warrants are outstanding, the Company 
shall continue the listing or trading of the Common Stock on the Nasdaq NMS 
or one of the other Approved Markets and comply in all respects with the 
Company's reporting, filing and other obligations under the bylaws or rules 
of the Approved Market on which the Common Stock is listed.  The Company 
shall cause the Common Shares and the Warrant Shares to be listed on the 
Nasdaq NMS no later than the registration of the Common Shares or the Warrant 
Shares under the Act, and at all times shall continue such listing(s) on one 
of the Approved Markets.  As used herein and in the Registration Rights 
Agreement, the Debenture and the Warrants, the term "EFFECTIVE REGISTRATION" 
shall mean that all registration obligations of the Company pursuant to the 
Registration Rights Agreement and this Agreement have been satisfied, all 
Registrable Securities (as defined in the Registration Rights Agreement) have 
been registered for resale by the Investors, such registration is not subject 
to any suspension or stop order, the prospectus for the Common Shares 
issuable upon conversion of the Debentures and the Warrant Shares issuable 
upon exercise of the Warrants is current and such Common Shares and Warrant 
Shares are listed for trading on one of the Approved Markets and such trading 
has not been suspended for any reason, none of the Company or any direct or 
indirect subsidiary of the Company is subject to any bankruptcy, insolvency 
or similar proceeding, and no Interfering Event (as defined in Section 2(b) 
of the Registration Rights Agreement) exists.

     3.2  DEBENTURES ON CONVERSION AND WARRANTS ON EXERCISE.

          (a)  Upon any conversion by an Investor (or then holder of 
Debentures) of the Debentures pursuant to the terms thereof, the Company 
shall issue and deliver to such Investor (or holder) within three (3) Trading 
Days of the Conversion Date (as defined in the Debenture) a new certificate 
or certificates for the number of Debentures which such Investor (or holder) 
has not yet elected to convert but which are evidenced in part by the 
certificate(s) submitted to the Company in connection with such conversion 
(with the number of and denomination of such new certificate(s) designated by 
such Investor or holder).

          (b)  Upon any partial exercise by an Investor (or then holder of 
the Warrants) of the Warrants, the Company shall issue and deliver to such 
Investor (or holder) within three (3) days of the date on which such Warrants 
are exercised, a new Warrant or Warrants representing the number of adjusted 
Warrant Shares, in accordance with the terms of Section 2 of the Warrants.


                                      11


     3.3  REPLACEMENT DEBENTURES AND WARRANTS.

          (a)  The certificate(s) representing the Debentures held by any 
Investor (or then holder) may be exchanged by such Investor (or such holder) 
at any time and from time to time for certificates with different 
denominations representing an equal aggregate number of Debentures, as 
requested by such Investor (or such holder) upon surrendering the same.  No 
service charge will be made for such registration or transfer or exchange.

          (b)  The Warrants will be exchangeable at the option of the 
Investor (or then holder of the Warrants) at the office of the Company for 
other Warrants of different denominations entitling the holder thereof to 
purchase in the aggregate the same number of Warrant Shares as are 
purchasable under such Warrants.  No service charge will be made for such 
transfer or exchange.

     3.4  EXPENSES.  The Company shall pay in immediately available funds, at 
the Closing and promptly upon receipt of any further invoices relating to 
same, all reasonable due diligence fees and expenses and attorneys' fees and 
expenses of Kleinberg, Kaplan, Wolff & Cohen, P.C. ("Investors' Counsel"), up 
to a maximum amount of $30,000, incurred by the Investors in connection with 
the preparation, negotiation, execution and delivery of this Agreement, the 
Registration Rights Agreement, the Debentures, the Warrants and the related 
agreements and documents and the transactions contemplated hereunder and 
thereunder.  At Closing, the Company shall pay the amount due for such fees 
and expenses (which may include fees and expenses estimated to be incurred 
for completion of the transaction including post-closing matters).  In the 
event such amount is ultimately less than the actual fees and expenses, the 
Company shall promptly pay such deficiency upon receipt of an invoice 
regarding same.

     3.5  SECURITIES COMPLIANCE. The Company shall notify the SEC and the 
Nasdaq NMS, in accordance with their requirements, of the transactions 
contemplated by this Agreement, the Debenture, the Registration Rights 
Agreement and the Warrants, and shall take all other necessary action and 
proceedings as may be required and permitted by applicable law, rule and 
regulation, for the legal and valid issuance of the Debentures hereunder, the 
Common Shares issuable upon conversion thereof, the Warrants and the Warrant 
Shares issuable upon exercise of the Warrants.

     3.6  DIVIDENDS OR DISTRIBUTIONS.  So long as any Debentures remain 
outstanding, the Company agrees that it shall not (a) declare or pay any 
dividends or make any distributions to any holder or holders of Common Stock, 
or (b) purchase or otherwise acquire for value, directly or indirectly, any 
Common Stock or other equity security of the Company.

     3.7  NOTICES.  The Company agrees to provide all holders of Debentures 
and Warrants with copies of all notices and information, including without 
limitation notices and proxy statements in connection with any meetings, that 
are provided to the holders of shares of Common Stock, contemporaneously with 
the delivery of such notices or information to such Common Stock holders.


                                      12


     3.8  USE OF PROCEEDS.  The Company agrees that the proceeds received by 
the Company from the sale of the Debentures hereunder shall be used for 
working capital purposes and an investment in Matridigm Corporation.

     3.9  RIGHT OF FIRST REFUSAL; ADJUSTMENTS.

          (a)  Until the expiration of twelve (12) months from the Closing 
Date, the Company shall not (i) sell or otherwise issue or deliver any shares 
of Common Stock or other equity securities or any securities which are 
convertible into or exchangeable for shares of its Common Stock or other 
equity securities or any convertible or exchangeable security, or any 
warrants or other rights to subscribe for or to purchase or any options for 
the purchase of shares of Common Stock or other equity securities to any 
party other than the Investors or their affiliates (a "THIRD PARTY") (other 
than in a bona-fide public offering conducted on the basis of a firm 
commitment underwriting with a price to the public of at least $10,000,000 
and other than shares or options issued or which may be issued pursuant to 
the Company's currently existing employee or director option plans and 
employee stock purchase plans as such plans may be amended from time to time 
consistent with practices of other companies in the high-technology sector, 
shares issued upon exercise of options, warrants or rights outstanding on the 
Closing Date listed in Section 2.1(c) of the Disclosure Schedule or shares 
issued in a Matridigm Transaction (as defined in Section 7.17), or (ii) 
obtain any equity or equity related financing from any Third Party, unless 
such offer, sale, issuance or financing ("FINANCING TRANSACTION") is first 
offered to the Investors.  The Company shall make such offer by providing 
each Investor with written notice of the Company's intention to enter into 
the Financing Transaction with such Third Party together with a term sheet 
identifying all such Third Parties and containing all the economic terms and 
significant provisions of the Financing Transaction (the "OFFER").  Such 
Offer shall be given with respect to each Financing Transaction negotiated by 
the Company with any Third Party.  The Investors shall have ten (10) business 
days from receipt of the Offer to deliver a written notice to the Company 
that the Investors wish to accept the Offer in whole but not in part (subject 
to satisfactory due diligence and reasonably acceptable definitive 
documentation) for the Financing Transaction.  If certain Investors choose 
not to participate, the other Investors may increase their participation on a 
proportional basis.  If the Investors reject the Offer entirely or fail to 
respond within such ten (10) business day period, then the Company shall be 
permitted to complete such Financing Transaction with the Third Party within 
thirty (30) days on terms and conditions identical to those contained in the 
Offer.  If any Financing Transaction is contemplated on terms and conditions 
not identical to those contained in the Offer or with definitive 
documentation not identical to that proposed by the Company with respect to 
the Offer or if such Financing Transaction is not consummated with such Third 
Party within 30 days, then such Financing Transaction shall be deemed a new 
Financing Transaction and the Investors shall again be entitled to receive an 
Offer for such Financing Transaction on such new terms and conditions (and/or 
with such new definitive documentation if applicable) or upon the same terms 
if the Third Party fails to consummate the Financing Transaction in the 
period specified in this sentence. The rights of the Investors under this 
paragraph 3.9 (a) as to any securities, instruments or rights issued which 
are exercisable or exchangeable for, or convertible into, shares of Common 
Stock, where (i) the exercise, exchange or conversion price is at a discount 
of 10% or greater from the then market price of the Common Stock, or (ii) 
holders of such securities, instruments or rights may acquire additional 
shares of Common Stock as a result of a 


                                      13


one-time or periodic adjustments to the exercise, exchange or conversion 
price, shall survive a Change of Control Transaction, as defined in the 
Debenture.

          (b)  If at any time within twelve (12) months from the Closing Date 
the Company issues Common Stock (or securities or rights exercisable or 
exchangeable for, or convertible into, Common Stock) in a private placement 
at a discount greater than the discount specified in Section 5(c) of the 
Debentures or at a ceiling, conversion, exercise or exchange price less than 
the Conversion Price (as defined in the Debentures and as adjusted pursuant 
to the terms thereof), then the Debentures will automatically (at the 
Investor's request) be adjusted to provide for such greater discount or lower 
or more favorable conversion, exercise or exchange price, as applicable.  
This paragraph 3.9 (b) shall not apply to issuances pursuant to currently 
existing employee or director option or stock purchase plans as such plans 
may be amended from time to time consistent with practices of other companies 
in the high-technology sector, issuances in a Matridigm Transaction or with 
respect to the items listed in Section 2.1(c) of the Disclosure Schedule.

     3.10 RESERVATION OF STOCK ISSUABLE UPON CONVERSION AND UPON EXERCISE OF 
THE WARRANTS.  The Company shall at all times reserve and keep available out 
of its authorized but unissued shares of Common Stock, solely for the purpose 
of effecting the conversion of the Debentures and the exercise of the 
Warrants, such number of its shares of Common Stock as shall from time to 
time be sufficient to effect the conversion of all outstanding Debentures and 
the full exercise of the Warrants and if at any time the number of authorized 
but unissued shares of Common Stock shall not be sufficient to effect the 
conversion of all the then outstanding Debentures, the full exercise of the 
Warrants, the Company will take such corporate action as may, in the opinion 
of its counsel, be necessary to increase its authorized but unissued shares 
of Common Stock to such number of shares as shall be sufficient for such 
purpose, including without limitation engaging in best efforts to obtain the 
requisite shareholder approval.  Without in any way limiting the foregoing, 
the Company agrees to reserve and at all times keep available solely for 
purposes of conversion of Debentures and the exercise of the Warrants such 
number of authorized but unissued shares of Common Stock that is at least 
equal to 200% of the aggregate shares issuable upon conversion of Debentures, 
and 200% of the aggregate shares issuable on exercise of Warrants, which 
number may be reduced by the number of Common Shares or Warrant Shares 
actually delivered pursuant to conversion of Debentures or exercise of the 
Warrants and shall be appropriately adjusted for any stock split, reverse 
split, stock dividend or reclassification of the Common Stock.  When the 
adjustments to the Conversion Price (as defined in the Debenture) pursuant to 
Sections 5(d) and 5(e) of the Debenture have been completed, the percentages 
set forth in the preceding sentence shall be reduced from "200%" to "103%".  
If the Company falls below the reserves specified in the immediately 
preceding sentence and does not cure such non-compliance within 30 days of 
its start, then the Investors will be entitled to the discount adjustments 
specified in Section 2(b)(i) of the Registration Rights Agreement. If at any 
time the number of authorized but unissued shares of Common Stock is not 
sufficient to effect the conversion of all the then outstanding Debentures or 
the full exercise of the Warrants, the Investors shall be entitled to, INTER 
ALIA, the premium price redemption rights provided in the Registration Rights 
Agreement.  The Company shall not be permitted to engage in any transaction 
if, after giving effect thereto, the Company would not be in compliance with 
the reservation requirements of this Section 3.10.


                                      14


     3.11 BEST EFFORTS.  The parties shall use their best efforts to satisfy 
timely each of the conditions described in Article IV of this Agreement.

     3.12 FORM D; BLUE SKY LAWS.  The Company agrees to file a Form D with 
respect to the Debentures, Warrants, Common Shares and Warrant Shares, as 
required under Regulation D and to provide a copy thereof to each Investor 
promptly after such filing.  The Company shall, on or before each Closing 
Date, take such action as the Company shall have reasonably determined is 
necessary to qualify the Debentures, Warrants, Common Shares and Warrant 
Shares for sale to the Investors at the applicable Closing pursuant to this 
Agreement under applicable securities or "blue sky" laws of the states of the 
United States (or to obtain an exemption from such qualification), and shall 
provide evidence of any such action so taken to each Investor on or prior to 
the Closing Date.

     3.13 NO SENIOR INDEBTEDNESS; LIMITATIONS ON ISSUANCE OF EQUITY.

          (a)  So long as any Debentures remain outstanding, the Company 
agrees that neither the Company nor any direct or indirect subsidiary of the 
Company shall create, incur, assume, guarantee, secure or in any manner 
become liable in respect of any indebtedness, except for Senior Debt as 
defined in the Debenture, debt owed to a financial institution which debt is 
unsecured other than by accounts receivable or trade payables incurred in the 
ordinary course of business consistent with past practices or debt pursuant 
to a Matridigm Transaction, unless junior to the Debentures in all respects.  
For purposes of this Section 3.13, "financial institution" excludes, without 
limitation, any investment company, or any entity that would be an investment 
company, but for the exclusions provided by Section 3(c)(1) or Section 
3(c)(7) of the Investment Company Act of 1940, as amended.

          (b)  Until the Registration Statement (as defined in the 
Registration Rights Agreement) has been declared effective by the SEC and the 
Common Shares are subject to Effective Registration, neither the Company nor 
any of its subsidiaries will issue any equity securities or instruments or 
rights convertible into or exchangeable or exercisable for any equity 
securities, except pursuant to current employee and director option and stock 
purchase plans in amounts and at prices consistent with past practice, in a 
Matridigm Transaction and with respect to items listed in Section 2.1(c) of 
the Disclosure Schedule.
                                     
                                 ARTICLE 4

                          CONDITIONS TO CLOSINGS

     4.1  CONDITIONS PRECEDENT TO THE OBLIGATION OF THE COMPANY TO SELL THE 
DEBENTURES.  The obligation hereunder of the Company to issue and/or sell the 
Debentures to the Investors at the Closing (unless otherwise specified) is 
subject to the satisfaction, at or before the Closing, of each of the 
applicable conditions set forth below.  These conditions are for the 
Company's sole benefit and may be waived by the Company at any time in its 
sole discretion.

          (a)  ACCURACY OF THE INVESTORS' REPRESENTATIONS AND WARRANTIES.  
The representations and warranties of each Investor will be true and correct 
in all material respects as of the date when made and as of the Closing Date 
as though made at that time (except for 


                                      15



representations and warranties as of an earlier date, which shall have been 
true and correct in all material respects as of such date).

          (b)  PERFORMANCE BY THE INVESTORS.  Each Investor shall have 
performed all agreements and satisfied all conditions required to be 
performed or satisfied by such Investor at or prior to the Closing.

          (c)  NO INJUNCTION. No statute, rule, regulation, executive order, 
decree, ruling or injunction shall have been enacted, entered, promulgated or 
endorsed by any court or governmental authority of competent jurisdiction 
which prohibits the consummation of any of the transactions contemplated by 
this Agreement or the Registration Rights Agreement or the Debentures or the 
Warrants.

     4.2  CONDITIONS PRECEDENT TO THE OBLIGATION OF THE INVESTORS TO PURCHASE 
THE DEBENTURES.  The obligation hereunder of each Investor to acquire and pay 
for the Debentures at the Closing (unless otherwise specified) is subject to 
the satisfaction, at or before the Closing, of each of the applicable 
conditions set forth below.  These conditions are for each Investor's benefit 
and may be waived by each Investor at any time in its sole discretion.

          (a)  ACCURACY OF THE COMPANY'S REPRESENTATIONS AND WARRANTIES.  The 
representations and warranties of the Company shall be true and correct in 
all material respects as of the date when made and as of the Closing Date as 
though made at that time (except for representations and warranties as of an 
earlier date, which shall have been true and correct in all material respects 
as of such date).

          (b)  PERFORMANCE BY THE COMPANY.  The Company shall have performed 
all agreements and satisfied all conditions required to be performed or 
satisfied by the Company at or prior to the Closing.

          (c)  NASDAQ NMS.  From the date hereof to the Closing Date, trading 
in the Company's Common Stock shall not have been suspended by the SEC or the 
Nasdaq NMS (or other Approved Market), and trading in securities generally as 
reported by the Nasdaq NMS (or other Approved Market) shall not have been 
suspended or limited, and the Common Stock shall not have been delisted from 
the Nasdaq NMS (or any other Approved Market where they are currently listed).

          (d)  NO INJUNCTION.  No statute, rule, regulation, executive, 
judicial or administrative order, decree, ruling or injunction shall have 
been enacted, entered, promulgated or endorsed by any court or governmental 
authority of competent jurisdiction which prohibits the consummation of any 
of the transactions contemplated by this Agreement or the Registration Rights 
Agreement or the Debenture or the Warrants.

          (e)  OPINION OF COUNSEL.  At the Closing, the Investors shall have 
received an opinion of counsel to the Company in the form attached hereto as 
Exhibit 4.2(e) and such other opinions, certificates and documents as the 
Investors or their counsel shall reasonably require incident to the Closing.


                                      16


          (f)  REGISTRATION RIGHTS AGREEMENT.  The Company and the Investors 
shall have executed and delivered the Registration Rights Agreement in the 
form and substance of Exhibit 4.2(f) attached hereto.

          (g)  ADVERSE CHANGES.  Since December 31, 1997, no event which had 
or is likely to have, in the reasonable judgment of the Investors, a Material 
Adverse Effect on the Company or any of its direct or indirect subsidiaries 
shall have occurred.

          (h)  OFFICER'S CERTIFICATE.  The Company shall have delivered to 
the Investors a certificate in form and substance satisfactory to the 
Investors and the Investors' Counsel, executed by an officer of the Company, 
certifying as to satisfaction of closing conditions, incumbency of signing 
officers, and the true, correct and complete nature of the Charter, By-Laws, 
good standing and authorizing resolutions of the Company.

          (i)  DEBENTURES AND WARRANTS.  The Investors shall have received 
certificates representing the Debentures and Warrants in the form and 
substance of Exhibit 1.1A and Exhibit 1.1B hereto.

          (j)  DUE DILIGENCE.  Each Investor shall have completed its 
financial, accounting, operational and legal due diligence in a manner 
satisfactory to such Investor in its sole discretion.

                                   ARTICLE 5

                                LEGEND AND STOCK

     The Company will issue one or more certificates representing the 
Debentures and the Warrants in the name of the Investor and in such 
denominations to be specified by the Investor prior to (or from time to time 
subsequent to) Closing. Each certificate representing the Debentures and the 
Warrants and any shares of Common Stock issued upon conversion or exercise 
thereof initially shall be stamped or otherwise imprinted with a legend 
substantially in the following form:

     THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 
1933 OR ANY STATE SECURITIES LAWS.  THEY MAY NOT BE SOLD OR OFFERED FOR SALE 
EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER SAID ACT AND ANY 
APPLICABLE STATE SECURITIES LAW OR AN APPLICABLE EXEMPTION FROM SUCH 
REGISTRATION REQUIREMENTS.

     The Company agrees to reissue Debentures and Warrants without the legend 
set forth above at such time as (i) the holder thereof is permitted to 
dispose of such Debentures and/or Warrants and Common Stock issuable upon 
conversion or exercise thereof pursuant to Rule 144(k) under the Act, or (ii) 
such Debentures and/or Warrants are sold to a purchaser or purchasers who (in 
the opinion of counsel to the seller or such purchaser(s), in form and 
substance reasonably satisfactory to the Company and its counsel) are able to 
dispose of such shares publicly without registration under the Act.


                                      17


     Prior to the Registration Statement (as defined in the Registration 
Rights Agreement) being declared effective, any Common Shares issued pursuant 
to conversion of Debentures or Warrant Shares issued upon exercise of the 
Warrants shall bear a legend in the same form as the legend indicated above.  
Upon such Registration Statement becoming effective, the Company agrees to 
promptly, but no later than three (3) business days thereafter, issue new 
certificates representing such Common Shares and Warrant Shares without such 
legend.  Any Common Shares issued pursuant to conversion of Debentures or 
Warrant Shares issued upon exercise of the Warrants after the Registration 
Statement has become effective shall be free and clear of any legends, 
transfer restrictions and stop orders.  Notwithstanding the removal of such 
legend, each Investor agrees to sell the Common Shares and Warrant Shares 
represented by the new certificates in accordance with the applicable 
prospectus delivery requirements or in accordance with an exemption from the 
registration requirements of the Act.

     Nothing herein shall limit the right of any holder to pledge these 
securities pursuant to a bona fide margin account or lending arrangement.

                                   ARTICLE 6

                                  TERMINATION

     6.1  TERMINATION BY MUTUAL CONSENT.  This Agreement may be terminated at 
any time prior to the Closing by the mutual written consent of the Company 
and each of the Investors.

     6.2  OTHER TERMINATION.  This Agreement may be terminated by action of 
the Board of Directors of the Company or by any of the Investors at any time 
if the Closing shall not have been consummated by the fifth business day 
following the date of this Agreement; provided, however, that the party (or 
parties) prepared to close shall retain its (or their) right to sue for any 
breach by the other party (or parties).

                                   ARTICLE 7

                                 MISCELLANEOUS

     7.1  STAMP TAXES.  The Company shall pay all stamp and other taxes and 
duties levied in connection with the issuance of the Debentures pursuant 
hereto, the Common Shares issued upon conversion thereof, and the Warrant 
Shares issued upon exercise of the Warrants.

     7.2  SPECIFIC PERFORMANCE; CONSENT TO JURISDICTION; JURY TRIAL.

          (a)  The Company and the Investors acknowledge and agree that 
irreparable damage would occur in the event that any of the provisions of 
this Agreement were not performed in accordance with their specific terms or 
were otherwise breached.  It is accordingly agreed that the parties shall be 
entitled to an injunction or injunctions to prevent or cure breaches of the 
provisions of this Agreement and to enforce specifically the terms and 
provisions hereof, this being in addition to any other remedy to which any of 
them may be entitled by law or equity.


                                      18


          (b)  THE COMPANY AND EACH OF THE INVESTORS (I) HEREBY IRREVOCABLY 
SUBMITS TO THE EXCLUSIVE JURISDICTION OF THE UNITED STATES DISTRICT COURT, 
THE NEW YORK STATE COURTS AND OTHER COURTS OF THE UNITED STATES SITTING IN 
NEW YORK COUNTY, NEW YORK FOR THE PURPOSES OF ANY SUIT, ACTION OR PROCEEDING 
ARISING OUT OF OR RELATING TO THIS AGREEMENT AND (II) HEREBY WAIVES, AND 
AGREES NOT TO ASSERT IN ANY SUCH SUIT ACTION OR PROCEEDING, ANY CLAIM THAT IT 
IS NOT PERSONALLY SUBJECT TO THE JURISDICTION OF SUCH COURT, THAT THE SUIT, 
ACTION OR PROCEEDING IS BROUGHT IN AN INCONVENIENT FORUM OR THAT THE VENUE OF 
THE SUIT, ACTION OR PROCEEDING IS IMPROPER.  THE COMPANY AND EACH OF THE 
INVESTORS CONSENTS TO PROCESS BEING SERVED IN ANY SUCH SUIT, ACTION OR 
PROCEEDING BY MAILING A COPY THEREOF TO SUCH PARTY AT THE ADDRESS IN EFFECT 
FOR NOTICES TO IT UNDER THIS AGREEMENT AND AGREES THAT SUCH SERVICE SHALL 
CONSTITUTE GOOD AND SUFFICIENT SERVICE OF PROCESS AND NOTICE THEREOF.  
NOTHING IN THIS PARAGRAPH SHALL AFFECT OR LIMIT ANY RIGHT TO SERVE PROCESS IN 
ANY OTHER MANNER PERMITTED BY APPLICABLE LAW.

          (c)  The Company and each Investor hereby waives all rights to a 
trial by jury.

     7.3  ENTIRE AGREEMENT; AMENDMENT.  This Agreement, together with the 
Registration Rights Agreement, the Warrants, the Debenture and the agreements 
and documents executed in connection herewith and therewith, contains the 
entire understanding of the parties with respect to the matters covered 
hereby and thereby and, except as specifically set forth herein or therein, 
neither the Company nor any Investor makes any representation, warranty, 
covenant or undertaking with respect to such matters.  No provision of this 
Agreement may be waived or amended other than by a written instrument signed 
by the party against whom enforcement of any such amendment or waiver is 
sought.

     7.4  NOTICES.  Any notice or other communication required or permitted 
to be given hereunder shall be in writing by mail, facsimile or personal 
delivery and shall be effective upon actual receipt of such notice.  The 
addresses for such communications shall be:

     to the Company:

     Zitel Corporation
     47211 Bayside Parkway
     Fremont, California  94538
     Attention:  Chief Financial Officer
     Facsimile:    (510) 440-8526


                                      19


     with copies to:

     Cooley Godward LLP
     One Maritime Plaza
     20th Floor
     San Francisco, California  94111
     Attention:   John L. Cardoza, Esq.
     Facsimile: (415) 951-3699

     to the Investors:

     To each Investor at the address and/or fax number set
     forth on Schedule I of this Agreement.

     with copies to:

     Kleinberg, Kaplan, Wolff & Cohen, P.C.
     551 Fifth Avenue, 18th Floor
     New York, New York 10176
     Attention:   Stephen M. Schultz, Esq.
     Facsimile: (212) 986-8866

     Any party hereto may from time to time change its address for notices by 
giving at least 10 days' written notice of such changed address to the other 
parties hereto.

     7.5  INDEMNITY.  Each party shall indemnify each other party against any 
loss, cost or damages (including reasonable attorney's fees but excluding 
consequential damages) incurred as a result of such parties' breach of any 
representation, warranty, covenant or agreement in this Agreement.

     7.6  WAIVERS.  No waiver by any party of any default with respect to any 
provision, condition or requirement of this Agreement shall be deemed to be a 
continuing waiver in the future or a waiver of any other provision, condition 
or requirement hereof, nor shall any delay or omission of any party to 
exercise any right hereunder in any manner impair the exercise of any such 
right accruing to it thereafter.

     7.7  HEADINGS.  The headings herein are for convenience only, do not 
constitute a part of this Agreement and shall not be deemed to limit or 
affect any of the provisions hereof.

     7.8  SUCCESSORS AND ASSIGNS.  Except as otherwise provided herein, this 
Agreement shall be binding upon and inure to the benefit of the parties and 
their successors and permitted assigns.  The parties hereto may amend this 
Agreement without notice to or the consent of any third party.  The Company 
may not assign this Agreement or any rights or obligations hereunder without 
the prior written consent of all Investors, except that the Company may 
assign this Agreement in connection with a Change of Control Transaction 
occurring in excess of forty-five (45) days after the Effectiveness Date (as 
defined in the Debenture) (such 45 days to be extended one day for every day 
after that date on which there is not Effective Registration), so long as 
such assignment places the Investors in a position economically equivalent to 
that in which they 


                                      20


would have been but for such assignment, in accordance with the terms of the 
Debentures and the Warrants.  Any Investor may assign this Agreement (in 
whole or in part) or any rights or obligations hereunder subject to the 
consent of the Company (such consent not to be unreasonably withheld) in 
connection with any sale or transfer of all or any portion of the Debentures 
or Warrants held by such Investor, provided that no consent of the Company 
will be required for any transfer or assignment by the Investor to (i) an 
affiliate or affiliates of the Investor or (ii) any person or entity whose 
investments are managed by an investment adviser that is the same as, or an 
affiliate of, the investment manager of the Investor.

     7.9  NO THIRD PARTY BENEFICIARIES.  This Agreement is intended for the 
benefit of the parties hereto and their respective permitted successors and 
assigns and is not for the benefit of, nor may any provision hereof be 
enforced by, any other person.

     7.10 GOVERNING LAW.  This Agreement shall be governed by and construed 
and enforced in accordance with the laws of the State of New York applicable 
to Agreements executed and to be performed entirely within such State.

     7.11 SURVIVAL.  The representations and warranties and the agreements 
and covenants of the Company and each Investor contained herein shall survive 
the Closing.

     7.12 EXECUTION.  This Agreement may be executed in two or more 
counterparts, all of which shall be considered one and the same agreement, it 
being understood that all parties need not sign the same counterpart.

     7.13 PUBLICITY.  The Company agrees that it will not disclose, and will 
not include in any public announcement, the name of any Investor without its 
consent, unless and until such disclosure is required by law or applicable 
regulation, and then only to the extent of such requirement.  The Company 
agrees that a copy of any public announcement regarding the matters covered 
by this Agreement or any agreement and document executed herewith and any 
public announcement (other than the filing of this Agreement as an exhibit on 
Form 8-K), including the name of an Investor will be approved by each 
Investor in advance of the release of such announcements.  The Company agrees 
that prior to the opening of trading on the day following the Closing Date, 
the Company shall issue a public announcement regarding the matters covered 
by this Agreement and related documents, which announcement shall be subject 
to the prior reasonable approval of the Investors.

     7.14 SEVERABILITY.  The parties acknowledge and agree that the Investors 
are not agents, affiliates or partners of each other, that all 
representations, warranties, covenants and agreements of the Investors 
hereunder are several and not joint, that no Investor shall have any 
responsibility or liability for the representations, warrants, agreements, 
acts or omissions of any other Investor, and that any rights granted to 
"Investors" hereunder shall be enforceable by each Investor hereunder.

     7.15 LIKE TREATMENT OF HOLDERS; REDEMPTION.  Neither the Company nor any 
of its affiliates shall, directly or indirectly, pay or cause to be paid any 
consideration (immediate or contingent), whether by way of interest, fee, 
payment for the redemption or conversion of Debentures or exercise of the 
Warrants, or otherwise, to any holder of Debentures or Warrants, 


                                      21


for or as an inducement to, or in connection with the solicitation of, any 
consent, waiver or amendment of any terms or provisions of the Debenture or 
this Agreement or the Registration Rights Agreement or the Warrants, unless 
such consideration is required to be paid to all holders of Debentures and 
Warrants bound by such consent, waiver or amendment whether or not such 
holders so consent, waive or agree to amend and whether or not such holders 
tender their Debentures or Warrants for redemption, conversion or exercise.  
The Company shall not, directly or indirectly, redeem any Debentures unless 
such offer of redemption is made pro rata to all holders of Debentures on 
identical terms.

     7.16 NO STRICT CONSTRUCTION.  The language used in this Agreement will 
be deemed to be the language chosen by the parties to express their mutual 
intent, and no rules of strict construction will be applied against any party.

     7.17 MATRIDIGM TRANSACTION.  As used herein and in the Debentures and 
the Warrants the term "Matridigm Transaction" shall mean any transaction or 
series of transactions whereby the Company acquires additional debt or equity 
securities of Matridigm Corporation, a California corporation, or the 
business of the Company and Matridigm are combined and shall include, without 
limitation, the issuance for cash of shares of the Common Stock of the 
Company with a fair market value not to exceed $2,000,000, as determined as 
of the purchase date and pursuant to one-time reset provisions agreed to 
between the Company and the purchasers, with the proceeds used to procure the 
release of obligations of the purchasers to guarantee obligations of 
Matridigm.


                           [SIGNATURE PAGES FOLLOW]


                                      22


     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be 
duly executed as of the date first above written.

                                    ZITEL CORPORATION

                                    By:       Anna M. McCann
                                        -----------------------------------
                                    Name:     Anna M. McCann
                                    Title:    V.P. Finance & Administration

                                    INVESTORS:

                                    HALIFAX FUND, L.P.

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President


                                    PALLADIN PARTNERS I, L.P.

                                    By:  PALLADIN GROUP L.P.
                                              Attorney-in-Fact

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President


                                    PALLADIN OVERSEAS FUND LIMITED

                                    By:  PALLADIN GROUP L.P.
                                              Attorney-in-Fact

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President


          [SIGNATURE PAGE TO ZITEL CORPORATION CONVERTIBLE SUBORDINATED
                         DEBENTURE PURCHASE AGREEMENT]


                                      23


                                    THE GLENEAGLES FUND COMPANY

                                    By:  PALLADIN GROUP L.P.
                                              Attorney-in-Fact

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President

                                    PALLADIN SECURITIES, LLC

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President


                                    COLONIAL PENN LIFE INSURANCE COMPANY

                                    By:  PALLADIN GROUP L.P.
                                              Attorney-in-Fact

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President

                                    LANCER SECURITIES LIMITED

                                    By:  PALLADIN GROUP L.P.
                                              Attorney-in-Fact

                                    By:       Jeffrey E. Devers
                                        -----------------------------------
                                    Name:     Jeffrey E. Devers
                                    Title:    President



          [SIGNATURE PAGE TO ZITEL CORPORATION CONVERTIBLE SUBORDINATED
                         DEBENTURE PURCHASE AGREEMENT]


                                      24