superzap

SuperZap definition

tool, IBM
An IBM utility program used to quickly patch operating system or application program executable code in preference to editing the source code and recompiling.
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-].
(2007-03-15)