Commodore Plus 4 - Page 175

ER, EL, and ERRS are variables used in error trapping routines. They
are usually only useful within a program. ER returns the last error en
countered since the program was RUN. EL is the line where the error
occurred. ERRS is a function which allows your program to print one
of the BASIC error messages. PRINT ERR$(ER) prints out the proper
error message.
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