Simple PERFORM

• This is simplest form of PERFORM statement. It is used to execute specified paragraph, and on completion of paragraph execution, control is returned back to the next statement following PERFORM
• Syntax:-
  PERFORM para-name
  Where, para-name is paragraph you want to execute
• Example:-
  In PROCUEDURE DIVISION,
  PARA-0. DISPLAY ‘IN PARA-0’. PERFORM PARA-1. DISPLAY ‘RETURNED FROM PARA-1’. STOP RUN. PARA-1. DISPLAY ‘IN PARA-1’.

SYSOUT display (output):-
IN PARA-0 IN PARA-1 RETURNED FROM PARA-1
• In above example, program first starts by executing first instruction of PARA-0, then since PERFORM is coded it will call PARA-1, once all instruction from PARA-1 is executed, control will be returned back to the next instruction following PERFORM and thus, in SYSOUT we can see ‘RETURNED FROM PARA-1’ is displayed. Above example is also demonstrated in flow chart form below.
• Using PERFORM statement versus GO TO statement
• PERFORM:
  In case if we had used GO TO in place of PERFORM then flow would be like:-
  GO TO:-
  
  Since GO TO is used, control is not returned back and thus statements coded in PARA-0 after GO TO will remain unexecuted