TRAP Examples

Example 1:

	TRAP	NOMASTER IF IO
	OPEN	APMASTER,"ACCTSPAY"

The TRAP instruction indicates that the program should CALL the subroutine NOMASTER if an IO error occurs. If the OPEN instruction fails because the file does not exist, an IO error occurs and the program calls NOMASTER.

Example 2:

	TRAP	NOPROGRM NORESET IF CFAIL
	CHAIN	"APAYUPTE"

The TRAP instruction indicates that the program should CALL the subroutine NOPROGRM if a CFAIL error occurs. If the CHAIN instruction fails (program does not exist, is a bad load module or insufficient system resources), a CFAIL error occurs and the program calls NOPROGRM. The trap remains set (NORESET) until a new TRAP CFAIL is set, a TRAPCLR CFAIL occurs or the program terminates.

Example 3:

	TRAP	HELP NORESET PRIOR IF F1
	KEYIN	"Enter Account Number: ",ACCTNO;
	...
HELP
	DISPLAY	.....
	KEYIN	ANS;
	RETURN

The TRAP instruction indicates that the program should CALL the subroutine HELP if an F1 function key is pressed during the KEYIN instruction. The PRIOR option causes the RETURN instruction in the HELP subroutine to return to the KEYIN instruction instead of the instruction after the KEYIN instruction. Note that the PRIOR option on TRAP is only active during a KEYIN instruction.

Example 4:

*
. Display the time every 60 seconds.
.
	...
	TRAP	GETTIME IF TIMER="60"
	...

#STATE	DIM	100
#TIME	DIM	5
GETTIME
	CLOCK	TIME,#TIME
	STATESAVE	#STATE
	DISPLAY	SETSWALL=1:1:76:80,HON,*DIOFF,#TIME;
	STATEREST	#STATE
	TRAP	GETTIME IF TIMER="60"
	RETURN

The TRAP instruction indicates that the program should CALL the subroutine GETTIME when sixty seconds has expired. The GETTIME routine retrieves the current system time. It then saves the current display state, outputs the time and then restores the display state. Finally, the routine resets the timer trap and returns.