HP 48g Graphing Calculator - Manual (Page 421)

Many conditions are automatically recognized by the HP 48 as error
conditions—and they’re automatically treated as errors in programs.
A command with an improper argument or an improper number of
arguments causes an error in a program. An out-oPrange result can
cause an error. An invalid calculator condition can cause an error.
Error trapping structures allow programs to intercept (or imp) error
conditions that otherwise would cause the program to abort.
IFERR...THEN...END
Enter this structure into a program by pressing (PRCl (NXT1 EFiFiOR
I F E R R . Its syntax is:
■ ii ... IFERR trap-clause THE'.H error-clause END ...
The commands in the error-clause are executed only if an error is
generated during execution of the trap-clause. If an error occurs in the
trap-clause, the error is ignored, the remainder of the trap-clause is
skipped, and program execution jumps to the error-clause. If no errors
occur in the trap-clause, the error-clause is skipped and execution
resumes after the END command.
Error Trapping Structures
IFERR...THEN...ELSE...END
29
Enter this structure into a program by pressing (PRG] (NXT 1
(f^ I F E R R . Its syntax is:
:! R Cj F:!
IFERR trap-clause
THEN error-clause -SEi normal-clause Er
The commands in the error-clause are executed only if an error is
generated during execution of the trap-clause. If an error occurs in the
trap-clause, the error is ignored, the remainder of the trap-clause is
skipped, and program execution jumps to the error-clause. If no errors
occur in the trap-clause, execution jumps to the normal-clause at the
completion of the trap-clause.
Programming the HP 48 29-15