New techniques in computer program verification;

              Hew Techniques
Anyone who has watched moonshots or other space-exploration
programs on television has undoubtedly
heard of Murphy's Law—at least as applied to the com­plex
systems associated with space missions. In briefest
terms, Murphy's Law holds that a system which can
fail, will. ^ F
Probabilities of failure depend on degrees of com­plexity
of the systems involved. This applies just as
logically to a business data-processing system as to
the systems that support a space mission. The big dif­ference,
of course, is that the stakes are different. If an
astronaut encounters an unexpected situation after his
vehicle has left the earth, the consequences—and the
dangers—are immediately apparent. However, in a busi­ness
data-processing system, major problems can exist
which are not apparent for a long time. This is where the
auditor comes in. The auditor must satisfy himself that
accounting principles are properly and uniformly ap­plied.
This holds true whether accounting records are
kept on computers or with pencil and paper. The audi­tor's
responsibility applies in either case. Accuracy can­not
be assumed.
In a business data-processing system, many manage­ment
people and auditors alike are lulled into com-in
Computer
plaisance by the automatic checking and verification
features built into computer hardware. Computers are
quite mechanically and functionally reliable. Therefore,
there is a tendency to assume that data produced by
computers are also automatically reliable. This is simply
not true.
A modern business data-processing system is a com­bination
of elements, including equipment, administra­tive
procedures, and processing programs. As has al­ready
been mentioned, features are incorporated into
most computers that provide a high degree of equipment
reliability without further examination by an auditor.
Administrative procedures associated with computer
systems can normally be examined through the applica­tion
of traditional audit techniques. The greatest chal­lenge
to the auditor requiring new techniques lies in the
verification of the computer programs that process the
financial data.
The programs used within business data-processing
systems are often referred to as "software." This term
distinguishes the functional instructions for the execut­ing
of computer operations, provided by programs, from
the equipment portion of a computer installation, re­ferred
to as "hardware." In general terms, there are two
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