ORDVAC

ORDVAC

The ORDVAC (Ordnance Discrete Variable Automatic Computer), is an early computer built by the University of Illinois for the Ballistic Research Laboratory at Aberdeen Proving Ground.[1] It was a successor to the ENIAC (along with EDVAC built earlier). It was based on the IAS architecture developed by John von Neumann, which came to be known as the von Neumann architecture. The ORDVAC was the first computer to have a compiler. ORDVAC passed its acceptance tests on March 6, 1952, at Aberdeen Proving Ground in Maryland.[2][3]: IV [4] Its purpose was to perform ballistic trajectory calculations for the US Military. In 1992, the Ballistic Research Laboratory became a part of the U.S. Army Research Laboratory.

Unlike the other computers of its era, the ORDVAC and ILLIAC I were twins and could exchange programs with each other. The later SILLIAC computer was a copy of the ORDVAC/ILLIAC series. J. P. Nash of the University of Illinois was a developer of both the ORDVAC and of the university's own identical copy, the ILLIAC, which was later renamed the ILLIAC I. Abe Taub, Sylvian Ray, and Donald B. Gillies[5] assisted in the checkout of ORDVAC at Aberdeen Proving Ground. After ORDVAC was moved to Aberdeen, it was used remotely by telephone by the University of Illinois for up to eight hours per night. It was one of the first computers to be used remotely and probably the first to routinely be used remotely.

The ORDVAC used 2178 vacuum tubes. Its addition time was 72 microseconds and the multiplication time was 732 microseconds. Its main memory consisted of 1024 words of 40 bits each, stored using Williams tubes. It was a rare asynchronous machine, meaning that there was no central clock regulating the timing of the instructions. One instruction started executing when the previous one finished.

Among the ORDVAC programmers were Martin Davis[6] and Elsie Shutt.

ORDVAC and its successor at Aberdeen Proving Ground, BRLESC, used their own unique notation for hexadecimal numbers. Instead of the sequence A B C D E F universally used today, the digits ten to fifteen were represented by the letters K S N J F L (King Sized Numbers Just For Laughs), corresponding to the teleprinter characters on five-track paper tape. The manual that was used by the military in 1958 used the name sexadecimal for the base 16 number system.

  1. ^ "The History of Computing at BRL". chimera.roma1.infn.it. Retrieved 2021-12-03.
  2. ^ Metropolis, Nicholas (2014-06-28). History of Computing in the Twentieth Century. Elsevier. pp. 359–360. ISBN 9781483296685.
  3. ^ Cite error: The named reference mv1 was invoked but never defined (see the help page).
  4. ^ "The ORDVAC". Digital Computer Newsletter. 4 (3). In use from 9 March: 4. 1952.{{cite journal}}: CS1 maint: others (link)[dead link‍]
  5. ^ "About Abraham Haskel Taub". Archived from the original on 2017-03-14. Retrieved 2017-03-14.
  6. ^ Jackson, Allyn (2008-05-01). "Interview with Martin Davis" (PDF). American Mathematical Society. Retrieved 2021-05-20.