HP 3000 Manuals HP 3000 Manuals
CALL
The CALL statement transfers control from the program unit that the
statement occurs in to a specified subprogram. The subprogram that
control is transferred to must be defined in the program or a run-time
error occurs.
The CALL statement can also transfer control to a user-defined multi-line
function. When used in this manner, the function is actually called as a
subprogram. The value returned by the function is discarded.
Syntax
CALL sub_name [(a_param [, a_param]...)]
Parameters
sub_name Subprogram that control is transferred to.
a_param Actual parameter - a value, a variable or an expression,
This parameter has a value of the appropriate type to be
assigned to the corresponding formal parameter in the
SUB statement that begins the subprogram or multi-line
function sub_name.
The CALL statement assigns the values of the actual
parameters to the corresponding formal parameters and
transfers control to the subprogram.
Execution of a SUBEXIT or SUBEND statement in the subprogram returns
control to the statement following the CALL statement provided there are
no pending softkey interrupt requests.
Example
10 READ A,B$
15 DATA 1,"Sample"
20 CALL Subrtn(A,B$) !Control goes to line 100
30 PRINT "Done"
99 END
100 SUBPROGRAM Subrtn(Number,String$)
110 IF Number<1 THEN SUBEXIT
120 FOR I=1 TO Number
130 PRINT RPT$(String$,Number)
140 NEXT I
150 SUBEND !Returns control to line 30
If a program has more than one subunit with the same name, the CALL
statement calls the first one that it finds. The following is the search
order:
1. Single-line function
2. Local external or intrinsic function
3. Internal multi-line function (one defined by the program)
4. Global external or intrinsic subunit
If the program is using softkey handling, the program checks for the key
after the subend statement, but before execution of the next main program
line. Thus, control can not go to the next line following the CALL, but
to a line specified by an ON KEY statement.