<
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)