Table | Control Computers Used for Bendix Photogrammetric Applications
Photogrammetric Add-Time,
Year Instrument Computer Type Memory Msec
1961 AP-1 Two computation 160 integrators 250
Analytical Plotter sections, serial 880 28-bit words
access, special-
purpose organization
1962 AP-2, AS-11A Two computation 320 integrators, 250
-63 Analytical Plotter sections, serial 1680 28-bit words
access, special-
purpose organization
1964 AP-C One computation 2560 28-bit words 19
Analytical Plotter section, serial
access, general-
purpose organization
1967 AS-11B Automated Two computation 512 integrators 156
Analytical Plotter sections, serial 4096 32-bit words
access, special-
purpose organization
1967 Hybrid One computation 8192 16-bit words 114*
Stereoplotter section, random
access, general-
purpose organization
1968 Automatic One computation 8192 18-bit words 48*
Comparator section, random
access, general-
purpose organization
1968 AS-11B-1 Automated One computation 8192 18-bit words 1.8*
Analytical Plotter section, random
access, general-
purpose organization
*Double-Precision
situations which must be handled is very large, and
correspondingly large files of programs and data must
be maintained. The number of inputs and outputs
may be high and input-output devices are frequently
remotely located. An input or output device may
provide or accept characters of a message at rates of
10 to 50 characters per second but no device does
this continuously. Thus, the demands of photogram-
metric instruments may be much smaller in the
amount of memory, but they are certainly much
greater in the necessary speed of response.
COMPUTER PROGRAMS FOR REAL-TIME OPERATION
The goal of most programming, including real-time
control programming, is efficient use of the com-
puter. Programming for real-time control applications
requires additional consideration of the program
repetition rate and the maximum response time; few
other computer programs have such stringent timing
requirements.
Program efficiency has two aspects: small memory
usage and short computation time. The amount of
memory needed and the computation time are some-
what interchangeable in programming; a suitable bal-
PROGRAMMING INSTRUMENTS
ance between the two must be sought for any given
real-time requirements. High program efficiency
permits use of an economical computer. Even in cases
where the computer has more capabilities than abso-
lutely needed, efficient programming still is desirable,
both to provide more than minimal system perform-
ance and to provide for later expansion of the pro-
gram. Small inefficiencies often can be tolerated for
such desirable purposes as making the program easier
to understand or easier to modify later.
Real-time control programs for photogrammetric
instruments do not change continually; a particular
program may be used for several years in several in-
struments without significant changes. Thus, it is
worthwhile to invest programming time to make the
original program as efficient as possible.
Finally, the cost of real-time programming usually
is small as a percentage of computer cost. Thus, a
small amount of extra effort in programming can
result in a large saving in computer cost.
These factors explain the emphasis on program
optimization. As computers become faster, memory
becomes less expensive, and computer programmers
become more highly paid, a point is reached at which
efficient programming loses some of its importance.
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