Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

Unexpected input/output data

A program should contain checks to ensure that any incorrect input and output data is detected before it can cause the program to fail.

Use the COPY option of the GET and PUT statements if you want to check values obtained by stream-oriented input and output. The values are listed on the file named in the COPY option. If no file name is given, SYSPRINT is assumed.

Use the VALID built-in function to check the validity of PICTURE and FIXED DECIMAL identifiers.

For additional information on features that can lead to unexpected I/O, see Porting applications between platforms. Many of the features that can lead to portability problems (such as differences in ASCII and EBCDIC collating sequences) can also lead to unexpected I/O for your PL/I programs.

Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide