How to specify parameters for your program (TSO)

To pass parameters to your program, append them to the ASMIDF command after a slash (⁄). IDF interprets anything that follows a slash as parameters that should be passed to the target program.

The parameter string is passed to the target in standard z/OS® EXEC PGM style. That is, R1 points to a word that points to a halfword length field that is followed by the parameter string itself.
Figure 1. Specifying parameters for your program (TSO)