National Bureau of Standards Wester Automatic Computer (SWAC)

Overview

     The School's computer users (faculty, staff and students) today turn on their desktops or plug in their laptops and have a gigahertz of speed, 256K main memory, 50 meg of disk storage, 17 inch monitor, scanner, speakers, access to the Internet, and word processing, spreadsheet, graphics, presentation, statistical functions, financial functions and other software readily available for immediate use. I (and my students) did not have these in the 1950s. Our first computer was SWAC. In fact, the School's first access to a computer on campus was to SWAC, although only a few of us used it.

      This overview is based on the Manual of the SWAC Computer System, U.S. Department of Commerce, National Bureau of Standards, Institute for Numerical Analysis, UCLA, Los Angeles, 1955. The manual is in the Southern Repository Library Facility on the UCLA Campus.

    Simplified Chart of SWAC (Section 2.1)

     The principal input is the card reader although a console is also available.

     Output is to a card punch, printer, or flexowriter.

     You can calculate how fast the machine added by dividing 15,625 into 1. Multiplication is slower. There is no divide instruction. (How do you divide when there is no explicit instruction?)

     The magnetic drum was a later addition to the original machine. It was a most welcome addition.

     There were 13 commands (or instructions) that could be executed by the control unit. The Chart says that each is a 4-address command.

     The high speed memory is a Williams Tube with a 256 word capacity and a 16 microsecond access time.

     This computer summary may raise some questions, like: What is a word? What is a Williams Tube? What does 256 word capacity mean? What is a 4-address command? Answers to these questions are given in Section 2.2 of the Manual. (Back to SWAC in detail.)