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6.2.3 ALTER Statement



The ALTER statement changes the transfer point specified in a GO TO statement.

The ALTER statement encourages the use of unstructured programming practices; the EVALUATE statement provides the same function as the ALTER statement and helps to ensure that your program will be well-structured.


    ________________________________________________________________________ 
   |                                                                        |
   | >>__ALTER____________________________________________________________> |
   |                                                                        |
   |    <________________________________________________________           |
   | >____procedure-name-1__TO__ ____________ __procedure-name-2_|_______>< |
   |                            |_PROCEED TO_|                              |
   |                                                                        |
   |________________________________________________________________________|
The ALTER statement modifies the GO TO statement in the paragraph named by procedure-name-1. Subsequent executions of the modified GO TO statement(s) transfer control to procedure-name-2.

procedure-name-1
Must name a Procedure Division paragraph that contains only one sentence: a GO TO statement without the DEPENDING ON phrase.

procedure-name-2
Must name a Procedure Division section or paragraph.

Before the ALTER statement is executed, when control reaches the paragraph specified in procedure-name-1, the GO TO statement transfers control to the paragraph specified in the GO TO statement. After execution of the ALTER statement, however, the next time control reaches the paragraph specified in procedure-name-1, the GO TO statement transfers control to the paragraph specified in procedure-name-2.

The ALTER statement acts as a program switch, allowing, for example, one sequence of execution during initialization and another sequence during the bulk of file processing.

Altered GO TO statements in programs with the INITIAL attribute are returned to their initial states each time the program is entered.


X Do not use the ALTER statement in programs that have the RECURSIVE
X attribute, in methods, or in AIX, OS/2, or Windows programs compiled with
X the THREAD option.

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