INTRODUCTION

















Writing CICS programs
---------------------

We write CICS program in much the same way as you write any other program. 
You can use COBOL, OO COBOL, C, C++, PL/I, or assembler language to write 
CICS application programs. Most of the processing logic is expressed in 
standard language statements, but you use CICS commands for some functions. 

Now, Let us write simple CICS program

Requirement  : Task 1 - CICS program to accept input from terminal 
               Task 2 - prefix string 'OUTPUT : ' to the input data
               send it back to the modified data to terminal


Program : 


 

  IDENTIFICATION DIVISION.
  PROGRAM-ID.    SAMCICS.
 *
  ENVIRONMENT DIVISION.
  DATA DIVISION.
  WORKING-STORAGE DIVISION.
 * 
  01  WS-INPUT.
      05 WS-TRAN-ID               PIC  X(4).
      05 WS-MESSAGE-I             PIC  X(70).
 *
  01  WS-OUTPUT.
      05 WS-TEXT                  PIC  X(8).
      05 WS-MESSAGE-O             PIC  X(70).
 *
  01  WS-MSG-LENGTH               PIC  S9(4)  COMP.
 *
  PROCEDURE DIVISION.
 *

      MOVE  74        TO   WS-MSG-LENGTH.               -------  (1)
 *
      EXEC CICS RECEIVE 				-------  (2)
                INTO(WS-INPUT)
                LENGTH(WS-MSG-LENGTH)
      END-EXEC.       
 *
      MOVE WS-MESSAGE-I    TO  WS-MESSAGE-O.            -------  (3)
      MOVE 'OUTPUT: '      TO  WS-TEXT.                 -------  (4)
      MOVE 78              TO  WS-MSG-LENGTH.           -------  (5)  
 *
      EXEC CICS SEND                                    -------  (6)
                FROM(WS-OUTPUT)
                LENGTH(WS-MSG-LENGTH)
                ERASE
      END-EXEC.
 *
      EXEC CICS RETURN                                  -------  (7)
      END-EXEC.
 *
      GOBACK.                                           -------  (8)
 *

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 Explanination -

 (1) Moving 74 to WS-MSG-LENGTH, ie., we are expecting 74 bytes of input 
     data from the terminal

 (2) All CICS commands embedded in COBOL program must be between EXEC CICS
     & END-EXECtags. Observe the RECEIVE command started with EXEC CICS 
     & ended with END-EXEC tag. Using this RECEIVE CICS command, program 
     can able to get the data passed from terminal. There are two options 
     used in this command.

      a) INTO - received data will be placed into WS-INPUT variable
      b) LENGTH - length of the data we are expecting to receive

 (3) Moving input data to part of output variable.

     if you observe one thing here, we are not move WS-INPUT to WS-OUPUT, 
     Why because, In WS-INPUT, first 4 bytes is transactionID, which is 
     used by CICS to identify our program to execute.  Rest of the data 
     we are passing to second part of output variable, first part of 
     output variable contains the value "OUTPUT:" in it.

    
 (4) Now our task is to add 'OUTPUT:' string to received data.
     for that we are moving 'OUPUT:' string to WS-TEXT which is part 
     of output variable WS-OUTPUT.


 (5) Since WS-OUTPUT variable size is 78, we are move 78 to WS-MSG-LENGTH
 (6) Now in step 6, we are using SEND command to send the the data in 
     WS-OUPUT variable to terminal.

     There are two options used in this command.
     a) FROM - specifing data location to be send to terminal
     b) LENGTH - specifing length of data being passed to terminal 
     c) ERASE - instructing to erase data on the screen, before printing 
                data that is being send.
     
 (7) RETURN command terminates current transaction.
 (8) GOBACK statement returns control to CICS.



 EXECUTING CICS PROGRAM
 ----------------------

  To execute above CICS program in CICS region, programmer should follow 
  these steps
  (1) Compile the program 
  (2) Move the load module to CICS load libraries. 
  (3) Define the Transaction identifier ( 1 to 4 bytes ) in PCT 
      (Program control table ) along with program name.
  (4) Define program name in PPT (Processing Program Table )
  (5) Login into CICS region
  (6) Enter transaction identifier defined in PCT.. 
      It will execute your program and return the results.