LOAN AND REGISTRATION RIGHT AGREEMENT


        Pursuant to this Agreement, dated October 3, 1996, INFODATA SYSTEMS INC.
(the "Company") and RICHARD M. TWOREK (the "Borrower") hereby agree as follows:

        1. Loan. The Company hereby loans the Borrower $70,000,  which loan will
bear  interest  at an annual  rate of 1% over prime,  adjusted  quarterly,  with
interest only payable  quarterly for three years at which time the loan is to be
repaid.  The Borrower  hereby  agrees to repay the loan in  accordance  with the
terms of the Promissory Note attached as Exhibit A hereto.

        2.  Registration  Right.  The  Company  hereby  agrees  to use its  best
efforts,  at its own  expense and within 30 days of the  Company's  receipt of a
written  request  received  from the Borrower  subsequent  to March 31, 1997 and
prior to October 11, 1998, to file a  Registration  Statement on a Form S-3 with
the Securities  and Exchange  Commission in order to register the 158,754 shares
of common stock,  par value $ .03 per share,  of the Company (the "Shares") held
by the Borrower,  which Shares were acquired by the Borrower from the Company on
October 11, 1995,  pursuant to the terms of an Asset and Purchase  Agreement and
Plan of  Reorganization,  dated as of October 6, 1995, among the Company,  Merex
Inc.  and the  Borrower  and two other  persons.  The Company  will use its best
efforts to maintain  the  effectiveness  of such  Registration  Statement  for a
period of three years following its effective date.

        IN WITNESS  WHEREOF,  the parties hereto have executed this Agreement on
the date first written above.


                                                   INFODATA SYSTEMS INC.


                                            By:    /s/ Harry Kaplowitz
                                                   -------------------
                                                   Harry Kaplowitz
                                                   President



                                                   RICHARD M. TWOREK

                                                   /s/ Richard M. Tworek
                                                   ---------------------
                                                   Richard M. Tworek




                                                               EXHIBIT A

                                 PROMISSORY NOTE

$70,000.00                                                     Fairfax, Virginia
                                                               October 3, 1996

        FOR VALUE RECEIVED,  the  undersigned,  RICHARD M. TWOREK (the "Maker"),
does hereby promise to pay to the order of INFODATA SYSTEMS INC. (the "Holder"),
the  principal sum of SEVENTY  THOUSAND  DOLLARS  ($70,000.00)  on September 30,
1999,  and to make quarterly  payments of interest  thereon at an annual rate of
one percent (1%) over prime, adjusted quarterly.

        1. Quarterly payments of interest only shall be made by the Maker to the
Holder on December 31, March 31, June 30 and September 30 of each year, with the
first such  quarterly  payment due on December  31, 1996 and the last  quarterly
payment due on September  30, 1999.  The  interest  rate for a quarterly  period
shall be based on the prime rate of interest  published by Chase Manhattan Bank,
N.A.,  on the first day of the quarterly  period.  The Maker shall make all such
payments to the Holder at 12150  Monument Drive (Suite 400),  Fairfax,  Virginia
22033 or such other address as may be designated by Holder.

        2. Payment of the $70,000 principal amount of this Promissory Note shall
be made by the Maker to the Holder on  September  30, 1999;  provided,  however,
that  this  Promissory  Note may be  prepaid  in  whole or in part at any  time,
without premium or penalty, with interest to the date of payment.

        3. If Maker fails to pay any installment of interest when due hereunder,
which  failure  continues  for a period  of ten  (10)  days  after  the due date
thereof,  then the principal amount of this Promissory Note and interest thereon
shall forthwith become due and payable  immediately without any notice or demand
therefor.

        4. This  Promissory  Note (i) is Exhibit A to the Loan and  Registration
Right Agreement,  dated October 3, 1996, between the Maker and the Holder,  (ii)
may not be changed, waived,  discharged or terminated except by an instrument in
writing  signed by the party against whom  enforcement  of such change,  waiver,
discharge or  termination  is sought,  (iii) shall be binding upon the Maker and
his heirs, executors, administrators, distributees and personal representatives,
(iv) shall inure to the benefit of Holder and its  successors  and assigns,  and
(v)  shall be  governed  by and  construed  in  accordance  with the laws of the
Commonwealth of Virginia.

        IN WITNESS  WHEREOF,  the Maker has caused  this  Promissory  Note to be
executed below.

                                                   /s/ Richard M. Tworek
                                                   ---------------------
                                                   Richard M. Tworek