Subprograms: CALL and USING

CALL and USING

CALL runs another compiled program. USING passes data items by reference by default, so the called program sees the caller's storage, not a copy:

CALL "PAYCALC" USING WS-HOURS WS-RATE WS-PAY.

The LINKAGE SECTION

The called program declares its parameters in the LINKAGE SECTION of DATA DIVISION. No VALUE clause and no storage is allocated here: the caller owns the memory:

DATA DIVISION. LINKAGE SECTION. 01 LS-HOURS PIC 9(3)V99. 01 LS-PAY PIC 9(7)V99.

CANCEL

CANCEL unloads a subprogram so the next CALL reloads it fresh, which clears any state it kept in WORKING-STORAGE. GOBACK returns from a subprogram; STOP RUN ends the whole run unit.

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Article author: Arthur Isaev