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The '''IBM 1401''' was a small [[mainframe]] introduced by [[International Business Machines|IBM]] in 1959. It was internally a digit/[[character]] at a time machine (a [[serial computer]], in a way), using decimal [[address]]ing; it supported from 1,400 up to 16,000 locations of [[main memory]]. (They held 8-bit [[byte]]s - although that term did not exist then - holding a six-bit character - similar to [[SIXBIT]], a [[parity]] bit, and a 'wordmark' bit, used to mark the end of variable sized [[operand]]s and [[instruction]]s.)

Instructions contained up to 4 fields: an [[operation code]] (one byte - the only mandatory field), an A operand address (three bytes), a B operand address (also three bytes), and a 'digit modifier' (one byte). Three bytes (locations) sufficed to hold any address, as characters were used to hold the first digit for addresses above '999'. Most instructions were memory to memory, which worked well with the 1401's variable-length operands.

It was intended primarily for the processing of data stored on [[punched card]]s (the primary medium of data storage in the business world at the time). It rapidly became the first computer used by many organizations around the world, and was the most common computer during most of the 1960s (in installations, not sales - IBM still mostly rented its products at that point). In the middle of the 1960s, half of all computers in the world were 1401s.

It was one of the first IBM computers to be built with [[transistor]]s, although its [[clock]] speed was a relatively sedate 11.5 µseconds; it also used [[core memory]]. Its 1403 chain [[line printer]] was outstanding; it was still a standard output [[peripheral]] over a decade later.

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==See also==

* [[IBM 701]]
* [[IBM 7094]]

==External links==

* [http://www.bitsavers.org/pdf/ibm/1401/ IBM 1401 Data Processing System] - documentation at [[Bitsavers]]
** [http://www.bitsavers.org/pdf/ibm/1401/A24-1401-1_1401_System_Summary_Sep64.pdf IBM 1401 System Summary]
** [http://www.bitsavers.org/pdf/ibm/1401/D24-1401-1_General_Information_Manual_IBM_1401_Feb60.pdf General Information Manual]
** [http://www.bitsavers.org/pdf/ibm/1401/A24-1403-5_1401_Reference_Apr62.pdf Reference Manual]
** [http://www.bitsavers.org/pdf/ibm/1401/X24-6532-0_1401_Program_Card_1961.pdf Program Card]
** [http://www.bitsavers.org/pdf/ibm/1401/A_Guide_to_1401_Programming_1961.pdf a guide to IBM 1401 programming]
* [https://ibm-1401.info/ The IBM 1401 Demo Lab and Restoration Project]
** [https://ibm-1401.info/Pics3/IBM1401_FactSheet.pdf Introduction to the IBM 1401]
** [https://ibm-1401.info/IBM1401_IEEE_SSCS_Mag_Jan2010-100DPI.pdf The Legendary IBM 1401 Data Processing System]
* [https://ed-thelen.org/comp-hist/ProgrammingTheIBM1401.pdf Programming the IBM 1401]

[[Category: IBM Mainframes]]

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	* [https://ed-thelen.org/comp-hist/ProgrammingTheIBM1401.pdf Programming the IBM 1401]		* [https://ed-thelen.org/comp-hist/ProgrammingTheIBM1401.pdf Programming the IBM 1401]

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 ** [http://www.bitsavers.org/pdf/ibm/1401/X24-6532-0_1401_Program_Card_1961.pdf Program Card]
 ** [http://www.bitsavers.org/pdf/ibm/1401/A_Guide_to_1401_Programming_1961.pdf a guide to IBM 1401 programming]
 * [https://ibm-1401.info/ The IBM 1401 Demo Lab and Restoration Project]
 ** [https://ibm-1401.info/Pics3/IBM1401_FactSheet.pdf Introduction to the IBM 1401]

IBM 1401 - Revision history

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