Flow Control

By default script file execution starts at the top of the file and then continues line by line until the end of the file has been reached. Although this is fine for some scripts in many cases you will need to control the flow of a script's execution. The OVM keywords that are used to control the flow of the script can be loosely divided into the categories unconditional, conditional, loop, and runtime error handling. Brief keyword descriptions are each given below. Follow the links for the full description of each keyword.

Unconditional Flow Control Keywords

call Explicitly call a function discarding its returned value.

eosub / !$$$$! Return to the script that called us with @include.

gosub Call an @subroutine.

goto Jump to an @label.

include Call another script but current script remains loaded.

pause Script immediately halts but remains loaded and can be recontinued.

quit Script immediately halts and Wozterm / Wozix exit also.

return Returns from the current @subroutine, @trap, @procedure, or @function.

run Call another script and current script is unloaded.

stop Script immediately halts and Wozix exits but Wozterm continues running.

Conditional Flow Control Keywords

if If a condition is true run the code that follows.

prompt Asks the user if to continue script execution.

Loop Flow Control Keywords

endloop Script immediately exits the innermost loop.

for Script executes a counting loop.

nextloop Script immediately continues to the next innermost loop iteration.

repeat Continue executing the code that follows until a condition is met.

while While a condition is met continue executing the code that follows.

Runtime Error Handling Keywords

check Turn runtime error checking on or off and optionally set an error trap.

geterrorflag Return the runtime error flag and the last runtime error number.

iferror Test (and reset) the runtime error flag and execute code that follows if it was set.

seterrorflag Set the runtime error flag and runtime error number.

trap Define a runtime error trapping subroutine for use with @check.

Operators

Contents

Procedures

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call	Explicitly call a function discarding its returned value.
eosub / !$$$$!	Return to the script that called us with @include.
gosub	Call an @subroutine.
goto	Jump to an @label.
include	Call another script but current script remains loaded.
pause	Script immediately halts but remains loaded and can be recontinued.
quit	Script immediately halts and Wozterm / Wozix exit also.
return	Returns from the current @subroutine, @trap, @procedure, or @function.
run	Call another script and current script is unloaded.
stop	Script immediately halts and Wozix exits but Wozterm continues running.

if	If a condition is true run the code that follows.
prompt	Asks the user if to continue script execution.

endloop	Script immediately exits the innermost loop.
for	Script executes a counting loop.
nextloop	Script immediately continues to the next innermost loop iteration.
repeat	Continue executing the code that follows until a condition is met.
while	While a condition is met continue executing the code that follows.

check	Turn runtime error checking on or off and optionally set an error trap.
geterrorflag	Return the runtime error flag and the last runtime error number.
iferror	Test (and reset) the runtime error flag and execute code that follows if it was set.
seterrorflag	Set the runtime error flag and runtime error number.
trap	Define a runtime error trapping subroutine for use with @check.