The SuperZAP program was a quick hack written by one IBM Engineer, possibly from IBM UK, in the late 1960s to directly fix executable files. He needed to fix a bug but it would have taken hours to rebuild the vast OS/360 executables.
The S/360 architecture has an instruction ZAP (Zero and Add Packed) for packed decmial arithmetic, that sets the byte at a given address to a given value. Superzap used this to write data given as a string of hex digits to a given location in an executable file in a matter of seconds.
Soon the IBM development labs were releasing all Programming Temporary Fixes (PTFs) to OS/360 in this form. OS/360 included a version called IMASPZAP or AMASPZAP which persisted through MVS, MVS/SP, MVS/XA, OS/390 and probably still remains in z/OS, the distant descendent of OS/360.
[Private 2004-02-05 e-mail from Chris Gage, IBM employee and SuperZap user, 1970-].