IBM Press release, March 27, 1953

Installation of the first production model of the International Business Machines Corporation's newest and most powerful high-speed electronic calculator, the "701," at the company's World Headquarters in New York was announced today.

Designed to shatter the time barrier confronting technicians working on vital defense projects, the 701 is being manufactured in IBM's Poughkeepsie, N.Y., plant where production-line techniques of assembly and standardization are used.

Composed of eleven compact and connected units known as IBM Electronic Data Processing Machines, the 701 is the first calculator of comparable capacity to be produced in quantity. A total of eighteen will be built within a year, all consigned to government agencies or defense industries.

The calculators, which will rent for $11,900 monthly or more, depending upon storage capacity, will be used for the calculation of radiation effects in atomic energy; for aerodynamic computations for planes and guided missiles, including vibration and stress analysis, design and performance computations for jet and rocket engines, propellers, landing gear, radomes, etc.; on studies related to the effectiveness of various weapons; and on steam and gas turbine design calculations. A company which has pioneered the use of high-speed digital computers for cost accounting with the IBM Card-Programmed Electronic Calculator, will use the 701 to speed and simplify the immense task of assembling and interpreting production cost data from its several plants. In government agencies the 701 will be used principally on classified problems.

The 701 installed at IBM in New York will be operated as a Technical Computing Bureau for organizations having problems involving mathematical computations. These will include problems similar to those listed above, as well as geophysical calculations and commercial studies. Test computations now in progress include a problem relating to the electronic charge distribution in the nitrogen molecule.

In preparation for the use of this machine by American industry, a staff of IBM scientists has been engaged for two years in planning the economical solution of typical problems. One result of this work is that users of the machine need no longer be concerned with tracing the position of the decimal point through problems involving thousands or millions of sequential arithmetical steps.

Using a "floating point" technique, the machine notes the position of the decimal point in the input numbers, keeps track of the point, and finally reports the position of the decimal point as the results are printed.

So much progress has been made in ease of use of electronic computers that in a course of only three weeks' duration, IBM is able to instruct its Scientific Computing Service users in the preparation of problems for the 701 and operation of the machine.

The 701 has at least 25 times the over-all speed but is less than one-quarter the size of IBM's Selective Sequence Electronic Calculator, which was dismantled to make room for its speedier successor.

During its five-year reign as one of the world's best-known "electronic brains," the SSEC solved a wide variety of scientific and engineering problems, some involving many millions of sequential calculations. Such other projects as computing the positions of the moon for several hundred years and plotting the courses of the five outer planets -- with resulting corrections in astronomical tables which had been considered standard for many years -- won such popular acclaim for the SSEC that it stimulated the imaginations of pseudo-scientific fiction writers and served as an authentic setting for such motion pictures as "Walk East on Beacon," a spy-thriller with an FBI background.

Though the 701 occupies the same quarters as the SSEC, which it rendered obsolete, it is not "built in" to the room as was its predecessor. Instead, it is smartly housed between serrated walls of soft-finished aluminum. A balconied conference room, overlooking the calculator and, separated from it by sloping plate glass, provides a vantage point for observing operations and discussing computations. Ample space is provided for writing the complex and abstract equations that are the stock in trade of engineers and scientists in an age of atomic energy and supersonic flight.

The 701 uses all three of the most advanced electronic storage, or "memory" devices -- cathode ray tubes, magnetic drums and magnetic tapes. The computing unit uses small versions of the familiar electronic tubes, which are able to count at millions of pulses a second. In addition, several thousand germanium diodes are used in place of vacuum tubes, with resultant savings in space and power requirements.

The 701 was designed for scientific and research purposes, and similar components are adaptable to the requirements of accounting and record-keeping. Research on commercial, data processing machines is under way.

The 701 is capable of performing more than 16,000 addition or subtraction operations a second, and more than 2,000 multiplication or division operations a second. In solving a typical problem, the 701 performs an average of 14,000 mathematical operations a second.

Internally, the 701 performs operations in the binary number system. All initial data and final results may be in the familiar decimal number system. High-speed conversion between number systems is handled automatically by the calculator.

But speed alone is not enough. To be able to solve the problems of enormous mathematical complexity attending the defense effort, a computer must also have prodigious storage capacity and extreme flexibility. Further, it must have input and output systems that are both fast and efficient.

When the outbreak of hostilities in Korea made the production of devices embodying all these components imperative, IBM was ready with the necessary prototypes. Its years of research and development in the field of computing already had produced the Automatic Sequence Controlled Calculator, first of the so-called "giant brains," and the Selective Sequence Electronic Calculator, as well as approximately 1500 Type 604 Electronic Calculators and Card-Programmed Electronic Calculators for business and industrial use.

The present emergency clearly defined the need for a calculator that would take a front-line position in the preparedness program -- one capable of solving hitherto insurmountable engineering and scientific computing problems and eliminating many costly and time-consuming trial-and-error methods, while helping to relieve the shortage of technically-trained personnel.

The new computer can solve problems involving partial differential equations, ordinary differential equations, integral equations, matrices and combinatorial analyses. Partial differential equations occur, for example, in calculating the rate of flow of heat in the skin of a supersonic missile; ordinary differential equations arise in calculating the expected flight characteristics of the missiles; integral equations arise in calculating radiation intensities; matrices arise in component analyses in petroleum products; and combinatorial analyses arise in strategic and tactical considerations.

The need for an electronic machine which will carry out thousands of operations a second is illustrated by the fact that the solution of a well-known partial differential equation useful in aircraft wing design requires 8,000,000 calculating steps per case.

The solution must be carried out step by step. Thus step 100 cannot be computed until the result of step 99 is known. Consequently, only one man, working with pencil and paper or one machine, can be occupied with the problem at any one time. The 701 completes the solution in a few minutes. A man working with a desk computer and using the same method would require seven years.

The banks of cathode ray tubes in the 701, known technically as electrostatic storage units, comprise the heart of the machine through which all information to and from all other components must pass.

The tubes -- each resembling a smaller version of' the picture tube used in television sets -- can store the equivalent of 20,000 decimal digits on their screens by means of the presence or absence of charged spots. In a few millionths of a second, any digit stored on a tube screen can be selected for use, with a scanning electronic beam "reading" the charges and converting them into electronic pulses. These pulses are interpreted as numbers or calculating instructions.

The computer's magnetic drums -- swiftly spinning cylinders surfaced with a material which can be easily magnetized -- can store the equivalent of 80,000 decimal digits, any of which are available for use thousands of times a minute.

The magnetic tapes used in the 701 are similar in appearance to those employed by home sound recorders. In the new computer, each reel of tape can store 2,000,000 digits. Since fresh tapes can readily be substituted for those "filled" with digits, magnetic tape storage in the 701 is unlimited, for all practical purposes.

Components of the 701 include an Electronic Analytical Control Unit, an Electrostatic Storage Unit, a Punched Card Reader, an Alphabetical Printer, a Punched Card Recorder, two Magnetic Tape Readers and Recorders, (each including two magnetic tapes), a Magnetic Drum Reader and Recorder, and units governing power supply and distribution.

A typical problem is handled by the 701 in this fashion:

All pertinent numbers, representing both the digits to be processed and instructions as to the procedure to be followed, are fed into the computer and automatically transmitted to the Electrostatic Storage Units.

The instant the machine has the data necessary to solve the problem, it begins computing. This is done by the arithmetic and control circuits of the Analytical Control Unit, which take numbers from the Electrostatic Storage Units according to instructions and perform any combination of arithmetic operations desired.

By means of the instructions provided the machine prior to the start of computing operations, the control circuits will make decisions as to the steps required to complete the solution of the problem without intercession by the operator.

When the computing is completed, step by step, the results are stored back in the Electrostatic Storage Units. If so directed in the preliminary instructions, the machine will then print the results by means of a 150-line-a-minute printer at the rate of 1,050 ten-digit numbers a minute. For compact storage and high-speed input and output, the 701 will transmit results to magnetic tapes at a rate equivalent to 1,250 ten-digit numbers a second. Also if desired, the machine will punch the results in standard punched cards at a rate equivalent to 2,400 ten-digit numbers a minute.

In the case of problems involving more digits than can be conveniently stored in the Electrostatic Storage Units, the figures and calculating instructions are stored on the magnetic drums and tapes. When these are needed for use by the arithmetic circuits, they are automatically transmitted to the electrostatic memory components and the operations proceed as outlined above.