Specify that files with the .REX extension contain REXX scripts. Specify that files with the .REX extension are to be searched for when a command is issued and in what order. Which directories are searched and in what order is determined by the PATH environment variable. You can specify whatever order you like, but traditionally, REXX files are searched for first. File extensions in Windows NT are not limited to three characters, so .REX is different from .REXX .
Advantages Produces no spurious output.
Can pass semicolon, comma, and equal sign characters to REXX program files. Requires no special initial set-up during each session. Is space efficient. It does not require any additional disk space. Requires no additional tasks when a program is created, copied, renamed, or deleted.