If your terminal is not an IBM® 3270 or equivalent, you can use the LINESIZE operand to specify the maximum number of characters allowed on one line of your terminal.

TERMINAL LINESIZE(40)

If you enter LINESIZE(80) and try to view a data set with its record format attribute (RECFM) set to U, specifying records of undefined length, the line is truncated at the 79th character. The truncated byte (80) is reserved for an attribute character.

REXX processing formats the output of the REXX SAY instruction and tracing output to one less than the value of the LINESIZE setting. The REXX LINESIZE() function also returns this amount.