View source for IBM 1620

The '''IBM 1620''' (formally the '''IBM 1620 Data Processing System'''; informally known as the '''CADET''', for 'Can't Add, Doesn't Even Try') was a relatively early small scientific computer (prior to the [[IBM System/360|360]], [[International Business Machines|IBM]] computers were specialized and separate for scientific and business applications) from IBM. It was one of the first IBM computers to be built with [[transistor]]s, and used [[core memory|magnetic core]] for its [[main memory]]. It was announced in October, 1959, and withdrawn in November, 1970; around two thousand were produced.

Its main memory was divided into 'locations' (intended for storage of numbers in [[binary-coded decimal|BCD]]); each location holds four [[bit]]s of data, a 'wordmark' bit (principally used to mark the end of variable sized [[operand]]s), and had a [[parity]] bit. Like its cousin, the business-oriented [[IBM 1401]], it supported variable-length operands. The standard 'module' was 20K locations; up tom two additional modules could be added.

[[Instruction]]s were 12 locations (72 bits) long, with a two-digit [[operation code|opcode]], and two 5-digit [[address]]es. All arithmetic [[operator|operations]] (''including addition'') were performed by table lookup, using tables stored in main memory (hence its nickname).

It used [[paper tape]] for [[input/output|I/O]], but also had a printing console device; a [[punched card]] reader/pounch was available as an option, as was a [[line printer]], and eventually either [[disk]] or up to 6 [[magnetic tape drive]]s for [[mass storage]]. 

Standard [[software]] included a [[FORTRAN]] [[compiler]].

{{semi-stub}}

==See also==

* [[IBM 704]]
* [[IBM 7094]]

==External links==

* [http://www.bitsavers.org/pdf/ibm/1620/ IBM 1620 Data Processing System] - documentation at [[Bitsavers]]
** [http://www.bitsavers.org/pdf/ibm/1620/IBM_1620_Product_Specifications_Jan60.pdf Preliminary Functional Specifications CADET Computer]
** [http://www.bitsavers.org/pdf/ibm/1620/A26-5718-0_IBM_1620_System_Summary.pdf IBM 1620 System Summary]
** [http://www.bitsavers.org/pdf/ibm/1620/A26-4500-2_1620ref_Jul61.pdf IBM 1620 Data Processing System Reference Manual]
** [http://www.bitsavers.org/pdf/ibm/1620/Basic_Programming_Concepts_and_the_IBM_1620_Computer_1962.pdf Basic Programming Concepts and the IBM 1620 Computer]
* [https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP1620.html 1620 Data Processing System]
* [http://www.physics.smu.edu/fattarus/ibm1620.html The IBM 1620 Model 1]
* [http://www.columbia.edu/cu/computinghistory/1620.html The IBM 1620 Data Processing System]
* [https://www.cs.utexas.edu/users/EWD/transcriptions/EWD00xx/EWD37.html A review of the IBM 1620 Data Processing System] - a brutal review of the 1620 by [[Edsger Dijkstra]]

[[Category: IBM Small Computers]]