Printronix ThermaLine Series - Manual (Page 347)

8–15 Error Codes
77 EXECUTE format or delimiter error
A format or delimiter error was detected in the Execute command; the
IGP/PGL will automatically revert to the Normal mode. This error is usually
caused by one or more of the following:
a. A missing semicolon;
b. A colon in place of a semicolon;
c. Too many or too few parameters in the command string;
d. Alpha characters instead of decimal digits in the parameters;
e. Page command misspelled when specifying the page number.
78 Insufficient memory to EXECUTE the form
Insufficient memory was available to recall and execute a form. The
IGP/PGL will automatically revert to the Normal mode.
79 Not defined.