Tuesday, June 13, 2006

John Backus on debugging

John Backus describes debugging, circa 1957:

In order to produce a program with built-in debugging facilities, it is a
simple matter for the programmer to write various PRINT statements, which
cause "snapshots" of pertinent information to be take at appropriate points in
his procedure, and insert these in the deck of cards comprising his original
FORTRAN program.  After compiling this program, running the resulting machine
program, and comparing the resulting snapshots with hand-calculated or
known values, the programmer can localize the specific area in his FORTRAN
program which is causing the difficulty.  After making the appropriate corrections
in the FORTRAN program he may remove the snap-shot cards and recompile
the final program or leave them in and recompile if the program is
not yet fully checked.

The FORTRAN Automatic Coding System
Proceedings of the Western Joint Computer Conference
Los Angeles, California, February 1957

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