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Description of the IBM 701

"Principles of Operation: Type 701 and Associated Equipment (IBM Manual, 1953)


Of  IBM's many important contributions to the field electronic business and scientific equipment, none has shown greater promise than the new class of equipment known as Electronic Data Processing Machines. This equipment, expanding electronics into previously untouched areas, has been made possible by drawing on IBM's tremendous reservoir of experience in electronics.

These new machines are being designed for the higher speeds and larger capacities demanded by problems of increasing complexity which confront business, industry, government, and science. These problems include procurement and supply, logistics, econometrics, production control, engineering development, and scientific research.

IBM Electronic Data Processing Machines will incorporate the newest devices for input, output, and storage, including magnetic tapes, magnetic drums, and cathode-ray tubes. Individual machines will be of portable size a specialized function. Some units will serve for control, arithmetic, and logical operations; others will provide for the input, output, or storing of data.

This manual describes a representative installation of present equipment—one that is intended primarily for engineering and scientific calculations. For simplicity, the complete name of this installation, IBM Electronic Data Processing Machines Type 701 and Associated Equipment, will
be abbreviated to 701.

Among the outstanding features of the 701 are its large-capacity high-speed electrostatic storage, intermediate magnetic drum storage, magnetic tape units, a versatile and fast input-output system, and computing speed characterized by a multiplication time of 456 microseconds.

In order to achieve maximum versatility, every function of the machine is under control of the stored program. This versatility allows the machine to execute instructions at the rate of about 14,000 per second on typical problems. Also functions such as input-output operation, which are determined by fixed circuitry on some computers, are under complete control of the program and, hence, under complete control of the operator. The great advantage of this system lies in the fact that a customer may build up a library programs which will accomplish his special applications at peak machine efficiency. No compromise in efficiency is necessary in the design of the machine to accommodate an average application. Furthermore, a customer may efficiently calculate on any 701 installation simply by using his own library of programs."

Personal Reflections - Roger Mills:

At North American Aviation, the IBM 701 was in a room by itself with a big glass window between the waiting room and the computer room.  Operators ran the cards through the card reader and printed the results or recorded the error code if the program stopped.  This output was given back to the programmer to debug and fix so the program could be submitted for another run.  There were two Happy Hours for which programmers signed up.. During the hour in the morning and hour in the afternoon,  The programmers would present their deck to the operator to run and watch the computer's lights flash. Sometimes you could tell how the run was going by watching the sequences of lights. Each run was limited to 10 minutes so only short jobs, usually subroutines could be checked out in this manner.  The incident I remember most was working with an older operator who had a degree in mathematics.  At that time, some clown thought that you had to have a college degree to operate the "Giant Brain."   It was a great step forward when they realized that the operators of the IBM card equipment made the best operators.  The mathematicians who operated the 701 wouldn't stay long due to boredom and the ones that stayed were to dumb to learn how to run the computer.  Well, the operator I am talking about is in the later category.  I was checking out a program during Happy Hour and was watching this mathematician put my cards in the card reader.  My program stopped and he turned to me and inform me the computer had stopped. Before I had a chance to record the stop address, he had cleared the console.  A week later, the powers that be realized he was never going to become an even semi-competent operator.  Of course nay of us programmers could give him instructions on what to do, but that wasn't allowed.  After the card operators began to run the computer, things got a lot better.