Commodore Plus 4 - Page 106

94 The BASIC Language
Line 30 resets the clock. Note the changes in the values of TI and TI$ when the
program is run again just after resetting.
RUN
1.65
000001
THEN Abbr. tH
Tells the computer what to do when an IF condition is true. See IF. . .THEN. . .
ELSE.
TRAP Abbr. tR
TRAP line number
Detects errors during execution of a BASIC program so that execution is not
aborted. When TRAP finds a program error, the error flag is set, and execution
passes to the line named in the TRAP command. This line can contain a routine
to help diagnose and solve the error.
After an error has been TRAPped, you can examine or display the following
information about the error:
Information Display Command
Number of the line that contains the error PRINT EL
Error message number PRINT ER
Error message that identifies the error PRINT ERR$(ER)
These commands can be included in the program at the line you name in the
TRAP command.
Return to normal program execution after a TRAP by issuing a RESUME
command. Never return by using a GOTO.
Parameter: line number or 0
The line number tells the computer where in the program to go if an error is
found. A value of 0 for a TRAP command turns off the error-trapping function in
the program.
TROFF Abbr. troF
Turns off the built-in error-tracing functions that are turned on by the TRON
command.