Editing Computer program (section)

===Very Large Scale Integration===
[[Image:Diopsis.jpg|thumb|right|A VLSI integrated-circuit [[die (integrated circuit)|die]] ]]
A major milestone in software development was the invention of the [[Very Large Scale Integration]] (VLSI) circuit (1964).<ref name="digibarn_bp">{{cite web
 | url=https://www.digibarn.com/stories/bill-pentz-story/index.html#story
 | title=Bill Pentz — A bit of Background: the Post-War March to VLSI
 | publisher=Digibarn Computer Museum
 | date=August 2008
 | access-date=January 31, 2022
 | archive-date=March 21, 2022
 | archive-url=https://web.archive.org/web/20220321183527/https://www.digibarn.com/stories/bill-pentz-story/index.html#story
 | url-status=live
 }}</ref> Following [[World War II]], tube-based technology was replaced with [[point-contact transistor]]s (1947) and [[bipolar junction transistor]]s (late 1950s) mounted on a [[circuit board]].<ref name="digibarn_bp"/> [[Invention of the integrated circuit|During the 1960s]], the [[aerospace]] industry replaced the circuit board with an [[integrated circuit chip]].<ref name="digibarn_bp"/>

[[Robert Noyce]], co-founder of [[Fairchild Semiconductor]] (1957) and [[Intel]] (1968), achieved a technological improvement to refine the [[Semiconductor device fabrication|production]] of [[field-effect transistor]]s (1963).<ref name="digital_age">{{cite book
 | url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA46
 | title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS
 | publisher=Johns Hopkins University Press
 | year=2002
 | isbn=9780801886393
 | access-date=February 3, 2022
 | archive-date=February 2, 2023
 | archive-url=https://web.archive.org/web/20230202181649/https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA46
 | url-status=live
 }}</ref> The goal is to alter the [[electrical resistivity and conductivity]] of a [[semiconductor junction]]. First, naturally occurring [[silicate minerals]] are converted into [[polysilicon]] rods using the [[Siemens process]].<ref name="osti">{{cite web
 | url=https://www.osti.gov/servlets/purl/1497235
 | title=Manufacturing of Silicon Materials for Microelectronics and Solar PV
 | publisher=Sandia National Laboratories
 | year=2017
 | access-date=February 8, 2022
 | last1=Chalamala
 | first1=Babu
 | archive-date=March 23, 2023
 | archive-url=https://web.archive.org/web/20230323163602/https://www.osti.gov/biblio/1497235
 | url-status=live
 }}</ref> The [[Czochralski process]] then converts the rods into a [[monocrystalline silicon]], [[Boule (crystal)|boule crystal]].<ref name="britannica_wafer">{{cite web
 | url=https://www.britannica.com/technology/integrated-circuit/Fabricating-ICs#ref837156
 | title=Fabricating ICs Making a base wafer
 | publisher=Britannica
 | access-date=February 8, 2022
 | archive-date=February 8, 2022
 | archive-url=https://web.archive.org/web/20220208103132/https://www.britannica.com/technology/integrated-circuit/Fabricating-ICs#ref837156
 | url-status=live
 }}</ref> The [[crystal]] is then thinly sliced to form a [[Wafer (electronics)|wafer]] [[Substrate (materials science)|substrate]]. The [[planar process]] of [[photolithography]] then ''integrates'' unipolar transistors, [[capacitor]]s, [[diode]]s, and [[resistor]]s onto the wafer to build a matrix of [[metal–oxide–semiconductor]] (MOS) transistors.<ref name="anysilicon">{{cite web
 | url=https://anysilicon.com/introduction-to-nmos-and-pmos-transistors/
 | title=Introduction to NMOS and PMOS Transistors
 | date=4 November 2021
 | publisher=Anysilicon
 | access-date=February 5, 2022
 | archive-date=6 February 2022
 | archive-url=https://web.archive.org/web/20220206051146/https://anysilicon.com/introduction-to-nmos-and-pmos-transistors/
 | url-status=live
 }}</ref><ref name="britannica_micropressor">{{cite web
 | url=https://www.britannica.com/technology/microprocessor#ref36149
 | title=microprocessor definition
 | publisher=Britannica
 | access-date=April 1, 2022
 | archive-date=April 1, 2022
 | archive-url=https://web.archive.org/web/20220401085141/https://www.britannica.com/technology/microprocessor#ref36149
 | url-status=live
 }}</ref> The MOS transistor is the primary component in ''integrated circuit chips''.<ref name="digital_age"/>

Originally, integrated circuit chips had their function set during manufacturing. During the 1960s, controlling the electrical flow migrated to programming a [[Diode matrix|matrix]] of [[read-only memory]] (ROM). The matrix resembled a two-dimensional array of fuses.<ref name="digibarn_bp"/> The process to embed instructions onto the matrix was to burn out the unneeded connections.<ref name="digibarn_bp"/> There were so many connections, [[firmware]] programmers wrote a ''computer program'' on another chip to oversee the burning.<ref name="digibarn_bp"/> The technology became known as [[Programmable ROM]]. In 1971, Intel [[stored-program computer|installed the computer program onto the chip]] and named it the [[Intel 4004]] [[microprocessor]].<ref name="intel_4004">{{cite web
 | url=https://spectrum.ieee.org/chip-hall-of-fame-intel-4004-microprocessor
 | title=Chip Hall of Fame: Intel 4004 Microprocessor
 | publisher=Institute of Electrical and Electronics Engineers
 | date=July 2, 2018
 | access-date=January 31, 2022
 | archive-date=February 7, 2022
 | archive-url=https://web.archive.org/web/20220207101915/https://spectrum.ieee.org/chip-hall-of-fame-intel-4004-microprocessor
 | url-status=live
 }}</ref>

[[Image:Slt1.jpg|thumb|right|IBM's System/360 (1964) CPU was not a microprocessor.]]
The terms ''microprocessor'' and [[central processing unit]] (CPU) are now used interchangeably. However, CPUs predate microprocessors. For example, the [[IBM System/360]] (1964) had a CPU made from [[IBM Solid Logic Technology|circuit boards containing discrete components on ceramic substrates]].<ref name="ibm_360">{{cite web
 | url=https://www.computer-museum.ru/books/archiv/ibm36040.pdf |archive-url=https://ghostarchive.org/archive/20221010/https://www.computer-museum.ru/books/archiv/ibm36040.pdf |archive-date=2022-10-10 |url-status=live
 | title=360 Revolution
 | publisher=Father, Son & Co.
 | year=1990
 | access-date=February 5, 2022
 }}</ref>