Commodore Plus 4 - Page 164

STOP ST0P
This statement halls the program. A message, BREAK IN LINE #,
where the # is the line number containing the STOR The program
can be re-started at the statement following STOP if you use the
CONT command. The STOP statement is usually used while de
bugging a program.
SYS address
The word SYS is followed by a decimal number or numeric variable —
in the range 0 to 65535. The program begins executing the machine
language program starting at that memory location. This is similar
to the USR function, but does not pass a parameter. See the Plus/4
Programmer's Reference Guide for information about machine
language programs. —
TRAP TRApl'/ne#|
When turned on. TRAP intercepts all error conditions (including the
STOP KEY) except "UNDEF'D STATEMENT ERROR". In Ihe event of
any execution error, the error flag is set, and execution is transferred
to the line number named in the TRAP statement. The line number in —
which the error occurred can be found by using the system variable
EL. The specific error condition is contained in system variable ER.
The string function ERRS(ER) gives the error message correspond
ing to any error condition ER.
NOTE: An error in a TRAP routine cannot be trapped.
The RESUME statement can be used to resume execution.
TRAP with no iine# argument turns off error TRAPping.
_
TRON TR0N
TRON is used in program debugging. This statement begins trace
mode. When you are in trace mode, as each statement executes, the —
line number of that statement is printed.
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