Null-terminated parameter string
This parameter list is used most easily from C, passing a string to BPXWDYN defined with a
#pragma for OS linkage, or extern "OS" for C++. This string should
not contain any control characters. The high bit is on in the parameter address word.

C usage might include the following statements:
typedef int EXTF();
#pragma linkage(EXTF,OS)
EXTF *bpxwdyn;
int rc;
bpxwdyn=(EXTF *)fetch("BPXWDYN");
rc=bpxwdyn("alloc fi(sysin) da(my.dataset) shr");