A label prefix declares a name as a procedure name, format name, or statement label, depending on the type of statement to which the prefix is attached.
A label prefix on a PROCEDURE statement declares a name as a procedure name. The name is declared in the block that contains the PROCEDURE statement, and its scope is that containing block and all blocks contained by the procedure. The declaration lists each parameter referenced by the PROCEDURE statement, as well as the data type specified by any RETURNS option in the PROCEDURE statement. For example:
E: PROCEDURE(A,B) RETURNS(POINTER); DECLARE A FIXED BINARY; DECLARE B FLOAT DECIMAL;
In this example, E is declared as a procedure name in the block that contains the PROCEDURE statement. The attributes of that declaration are RETURNS(pointer) and ENTRY(fixed binary, float decimal).
The label prefix on a FORMAT statement declares a name as a format name. The name is declared in the block that contains the FORMAT statement and all contained blocks. A format name is not a statement label and cannot be used in a GOTO statement. A format name can be used only in a format statement.
The label prefix of a PROCEDURE or FORMAT statement cannot be sub- scripted.
A label prefix attached to statements other than PROCEDURE or FORMAT statements declares a name as a statement label. The declaration is established in the block that contains the statement to which the prefix is attached. For example, a label prefix attached to a BEGIN statement is declared in the block that contains the BEGIN statement and its scope is that containing block and all blocks contained by the BEGIN statement.
The label prefix of a PROCEDURE or FORMAT statement cannot be sub- scripted; however, label prefixes attached to statements other than PROCEDURE or FORMAT may be subscripted by a single optionally signed integer constant. Within its scope, all occurrences of a given name used in this manner must be subscripted, and all such prefixes collectively constitute a declaration of the name as an array of statement labels. For example:
GOTO CASE(K); CASE(1): . . . CASE(2): . . . CASE(3): . . . CASE(6): . . .
In this example, CASE is declared as an array of statement labels whose bounds are (1:6) and whose fourth and fifth elements are undefined. Defining arrays with undefined elements is not recommended, as it produces unpredictable results.
An array of statement labels cannot be used as an array value, but its elements can be used in any context that permits a statement label.
Procedure names, format names, and statement labels cannot be declared in a DECLARE statement in the same block, except that the names may be used as the structure member names.
Names of external procedures that are part of another program module must be declared by a DECLARE statement if they are to be referenced by the current program module. (For more information, see the section Modules.) Only external procedure names can be declared by a DECLARE statement.