AMENDMENT NO. ONE TO AGREEMENT AND PLAN OF MERGER
 
  THIS AMENDMENT NO. ONE (this "Amendment") is made and entered into as of 
November 7, 1997, by and among NATIONAL DATA CORPORATION ("NDC"), a Delaware 
corporation; DUNKIRK, INC. ("Sub"), a Delaware corporation; and SOURCE 
INFORMATICS INC. ("Source"), a Delaware corporation. 
 
                                    Preamble
 
  WHEREAS, NDC, Sub and Source entered into an Agreement and Plan of Merger 
dated as of August 20, 1997 (the "Agreement"), which, among other things, 
provided that NDC would acquire Source pursuant to the merger of Sub with and 
into Source (the "Merger"); and 
 
  WHEREAS, pursuant to Section 9.2 (h)(ii) of the Agreement, it is a condition 
to NDC's obligation to consummate the Merger that Source and Walsh 
International Inc. ("Walsh") execute and deliver to NDC a licensing arrangement 
between Source and Walsh relating to operations of Walsh in Asia (the "East 
Asia License Agreement"); and 
 
  WHEREAS, NDC, Source and Walsh have agreed to terminate negotiations with 
respect to the East Asia License Agreement and NDC, Sub and Source have agreed 
to remove the consummation of such agreement from the conditions precedent to 
consummation of the Merger; and 
 
  WHEREAS, NDC, Sub and Source desire to amend the Agreement to reflect the 
elimination of such condition; and 
 
  WHEREAS, NDC, Sub and Source are of the opinion that the foregoing is in the 
best interests of the parties and their respective stockholders. 
 
  NOW, THEREFORE, in consideration of the above and the mutual warranties, 
representations, covenants, and agreements set forth herein, the parties agree 
as follows: 
 
  A. Section 9.2(h) of Article 9 of the Agreement shall be deleted in its 
entirety and replaced with the following: 
 
  (h) Additional Agreements. Each of the following agreements, in the form 
attached hereto as an Exhibit, with such additions and changes as may be 
approved by NDC and all parties thereto, shall have been executed and delivered 
to NDC: 
 
(i) Source Europe License Agreement-Exhibit 7.
(ii) Source Europe Transition Services Agreement-Exhibit 8.
(iii) Assignment of Lease for Source property in Newtown, PA-Exhibit 9.
(iv) Sublease for use of property in Newtown, PA-Exhibit 10.
(v) Sublease for use of property in Phoenix, AZ-Exhibit 11.
(vi) SL Services Agreement-Exhibit 12.
 
  B. Section 9.2(j) of Article 9 of the Agreement shall be deleted in its 
entirety and replaced with the following: 
 
  (j) Indemnification Waivers. Each director and officer of Source shall have 
executed and delivered to NDC Waivers in substantially the form of Exhibit 13 
which will provide that such director or officer release their rights of 
indemnification under the bylaws of Source or Sub or the DGCL or otherwise with 
respect to claims arising from their acting or failing to act in connection 
with the Divestiture or with the allocation of consideration to be paid by NDC 
pursuant to the transactions contemplated by this Agreement and the PMSI 
Agreement, except and to the extent such is covered by directors' and officers' 
insurance. 
 
  C. Section 9.3(d) of Article 9 of the Agreement shall be deleted in its 
entirety and replaced with the following: 
 
  (d) Opinion of Counsel. Source shall have received an opinion of either the 
General Counsel of NDC or Alston & Bird LLP, counsel to NDC, dated as of the 
Effective Time, in form reasonably acceptable to Source, as to the matters set 
forth in Exhibit 14. 

 
  D. The definition of "Exhibits" in Section 12.1 of Article 12 of the 
Agreement shall be deleted in its entirety and replaced with the following: 
 
  "Exhibits" 1 through 14, inclusive, shall mean the Exhibits so marked, copies 
of which are attached to this Agreement. Such Exhibits are hereby incorporated 
by reference herein and made a part hereof, and may be referred to in this 
Agreement and any other related instrument or document without being attached 
hereto. 
 
  E. The "List of Exhibits" shall be deleted in its entirety and replaced with 
the following: 
 
                                LIST OF EXHIBITS
 
Exhibit
 Number Description
- ------- ------------------------------------------------------------------
   1.   Form of Escrow Agreement. ((S) 4.3).
   2.   Form of Stockholders' Voting Agreement. ((S) 5.21).
   3.   Form of agreement of affiliates of Source. ((S) 8.12).
   4.   Matters as to which Reboul, MacMurray, Hewitt, 
         Maynard & Kristol will opine. ((S) 9.2(d)). 
   5.   Terms of Employment Agreements. ((S) 9.2(f)).
   6.   Form of Noncompetition Agreement. ((S) 9.2(g)).
   7.   Form of Source Europe License Agreement.       
   8.   Form of Source Europe Transition Services Agreement.
   9.   Form of Assignment of Lease for Source property in Newtown, PA. 
  10.   Form of Sublease for use of property in Newtown, PA.
  11.   Form of Sublease for use of property in Phoenix, AZ.
  12.   Form of SL Services Agreement.                      
  13.   Form of Waiver. ((S) 9.2(k)).                       
  14.   Matters as to which Alston & Bird LLP will opine. ((S) 9.3(d)). 
 
  All capitalized terms contained in this Amendment and no otherwise defined 
shall have the meaning ascribed to them in the Agreement. 

  IN WITNESS WHEREOF, each of the Parties has caused this Agreement to be 
executed on its behalf and its corporate seal to be hereunto affixed and 
attested by officers thereunto as of the day and year first above written. 
 
National Data Corporation
 
                             By: /s/ E. Michael Ingram
                                ------------------------------------- 
                             Name: E. Michael Ingram
                             Title: Senior Vice President
 
                             Dunkirk, Inc.
 
                             By: /s/ E. Michael Ingram
                                -------------------------------------
                             Name: E. Michael Ingram
                             Title: Senior Vice President
 
                             Source Informatics Inc.
 
                             By: /s/ Warren J. Hauser
                                -------------------------------------
                             Name: Warren J. Hauser
                             Title: Vice President