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The console of the BRLESC computer (US Army photo)
BRLESC hardware (right) compared to its predecessors

The BRLESC I (Ballistic Research Laboratories Electronic Scientific Computer) was a first-generation electronic computer built by the United States Army's Ballistic Research Laboratory (BRL) at Aberdeen Proving Ground with assistance from the National Bureau of Standards (now the National Institute of Standards and Technology), and was designed to take over the computational workload of EDVAC and ORDVAC, which themselves were successors of ENIAC. It began operation in 1962.

BRLESC was designed primarily for scientific and military tasks requiring high precision and high computational speed, such as ballistics problems, army logistical problems, and weapons systems evaluations. It contained 1727 vacuum tubes and 853 transistors and had a memory of 4096 72-bit words. BRLESC employed punched cards, magnetic tape, and a magnetic drum as input-output devices, which could be operated simultaneously.

It was capable of five million (bitwise) operations per second. A fixed point addition took 5 microseconds, a floating-point addition took 5 to 10 microseconds, a multiplication (fixed or floating-point) took 25 microseconds, and a division (fixed or floating-point) took 65 microseconds. (These times are including the memory access time, which was 4-5 microseconds.)

BRLESC and its predecessor, ORDVAC, 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, corresponding to the teletypewriter characters on five-track paper tape.

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