You access information in the PARM field of an EXEC statement by
referring to the contents of general register 1. If you do not specify
the PARM field of the JCL EXEC statement, register 1 and register
15 contain the same value on initial entry.
When control is given to the program, general register 1 contains
the address of a fullword which, in turn, contains the address of
the data area containing the information.
The data area consists of a halfword containing the count (in binary) of the number of
information characters, followed by the information field. The information field is aligned to a
fullword boundary. Figure 1 shows how the PARM field information is
structured. Figure 1. Access to PARM field
