Editing Computer program (section)

===Stored-program computers===
Instead of plugging in cords and turning switches, a [[stored-program computer]] loads its instructions into [[Random-access memory|memory]] just like it loads its data into memory.<ref name="eniac-ch6-p120">{{cite book
  | last = McCartney
  | first = Scott
  | title = ENIAC – The Triumphs and Tragedies of the World's First Computer
  | publisher = Walker and Company
  | year = 1999
  | page = [https://archive.org/details/eniac00scot/page/120 120]
  | isbn = 978-0-8027-1348-3
  | url = https://archive.org/details/eniac00scot/page/120
  }}</ref> As a result, the computer could be programmed quickly and perform calculations at very fast speeds.<ref name="eniac-ch6-p118">{{cite book
  | last = McCartney
  | first = Scott
  | title = ENIAC – The Triumphs and Tragedies of the World's First Computer
  | publisher = Walker and Company
  | year = 1999
  | page = [https://archive.org/details/eniac00scot/page/118 118]
  | isbn = 978-0-8027-1348-3
  | url = https://archive.org/details/eniac00scot/page/118
  }}</ref> [[Presper Eckert]] and [[John Mauchly]] built the ENIAC. The two engineers introduced the ''stored-program concept'' in a three-page memo dated February 1944.<ref name="eniac-ch6-p119">{{cite book
  | last = McCartney
  | first = Scott
  | title = ENIAC – The Triumphs and Tragedies of the World's First Computer
  | publisher = Walker and Company
  | year = 1999
  | page = [https://archive.org/details/eniac00scot/page/119 119]
  | isbn = 978-0-8027-1348-3
  | url = https://archive.org/details/eniac00scot/page/119
  }}</ref> Later, in September 1944, [[John von Neumann]] began working on the ENIAC project. On June 30, 1945, von Neumann published the ''[[First Draft of a Report on the EDVAC]]'', which equated the structures of the computer with the structures of the human brain.<ref name="eniac-ch6-p118"/> The design became known as the [[von Neumann architecture]]. The architecture was simultaneously deployed in the constructions of the [[EDVAC]] and [[EDSAC]] computers in 1949.<ref name="eniac-ch6-p123">{{cite book
  | last = McCartney
  | first = Scott
  | title = ENIAC – The Triumphs and Tragedies of the World's First Computer
  | publisher = Walker and Company
  | year = 1999
  | page = [https://archive.org/details/eniac00scot/page/123 123]
  | isbn = 978-0-8027-1348-3
  | url = https://archive.org/details/eniac00scot/page/123
  }}</ref><ref>{{Citation |last=Huskey |first=Harry D. |title=EDVAC |date=2003-01-01 |encyclopedia=Encyclopedia of Computer Science |pages=626–628 |url=https://dl.acm.org/doi/10.5555/1074100.1074362 |access-date=2025-04-25 |place=GBR |publisher=John Wiley and Sons Ltd. |isbn=978-0-470-86412-8}}</ref>

The [[IBM System/360]] (1964) was a family of computers, each having the same [[instruction set architecture]]. The [[IBM System/360 Model 20|Model 20]] was the smallest and least expensive. Customers could upgrade and retain the same [[application software]].<ref name="sco-ch1-p21">{{cite book
  | last = Tanenbaum
  | first = Andrew S.
  | title = Structured Computer Organization, Third Edition
  | publisher = Prentice Hall
  | year = 1990
  | page = [https://archive.org/details/structuredcomput00tane/page/n42 21]
  | isbn = 978-0-13-854662-5
  | url = https://archive.org/details/structuredcomput00tane
  | url-access = registration
  }}</ref> The [[IBM System/360 Model 195|Model 195]] was the most premium.  Each System/360 model featured [[multiprogramming]]<ref name="sco-ch1-p21"/>—having multiple [[Process (computing)|processes]] in [[random-access memory|memory]] at once. When one process was waiting for [[input/output]], another could compute.

IBM planned for each model to be programmed using [[PL/1]].<ref name="cpl_3rd-ch2-27">{{cite book
  | last = Wilson
  | first = Leslie B.
  | title = Comparative Programming Languages, Third Edition
  | publisher = Addison-Wesley
  | year = 2001
  | page = 27
  | isbn = 0-201-71012-9
}}</ref> A committee was formed that included [[COBOL]], [[Fortran]] and [[ALGOL]] programmers. The purpose was to develop a language that was comprehensive, easy to use, extendible, and would replace Cobol and Fortran.<ref name="cpl_3rd-ch2-27"/> The result was a large and complex language that took a long time to [[compile]].<ref name="cpl_3rd-ch2-29">{{cite book
  | last = Wilson
  | first = Leslie B.
  | title = Comparative Programming Languages, Third Edition
  | publisher = Addison-Wesley
  | year = 2001
  | page = 29
  | isbn = 0-201-71012-9
}}</ref>

[[File:Dg-nova3.jpg|thumb|Switches for manual input on a [[Data General Nova]] 3, manufactured in the mid-1970s]]
Computers manufactured until the 1970s had front-panel switches for manual programming.<ref name="osc-ch1-p6">{{cite book
  | last = Silberschatz
  | first = Abraham
  | title = Operating System Concepts, Fourth Edition
  | publisher = Addison-Wesley
  | year = 1994
  | page = 6
  | isbn = 978-0-201-50480-4
}}</ref> The computer program was written on paper for reference. An instruction was represented by a configuration of on/off settings. After setting the configuration, an execute button was pressed. This process was then repeated. Computer programs also were automatically inputted via [[paper tape]], [[punched cards]] or [[9-track tape|magnetic-tape]]. After the medium was loaded, the starting address was set via switches, and the execute button was pressed.<ref name="osc-ch1-p6"/>