Editing Computer multitasking (section)

== Multiprogramming ==
In the early days of computing, [[CPU time]] was expensive, and [[peripheral]]s were very slow. When the computer ran a program that needed access to a peripheral, the central processing unit (CPU) would have to stop executing program instructions while the peripheral processed the data. This was usually very inefficient. Multiprogramming is a computing technique that enables multiple programs to be concurrently loaded and executed into a computer's memory, allowing the CPU to switch between them swiftly. This optimizes CPU utilization by keeping it engaged with the execution of tasks, particularly useful when one program is waiting for I/O operations to complete.

The [[Bull Gamma 60]], initially designed in 1957 and first released in 1960, was the first computer designed with multiprogramming in mind. Its architecture featured a central memory and a Program Distributor feeding up to twenty-five autonomous processing units with code and data, and allowing concurrent operation of multiple clusters.

Another such computer was the [[LEO (computer)#Applications and successors|LEO III]], first released in 1961. During [[batch processing]], several different programs were loaded in the computer memory, and the first one began to run. When the first program reached an instruction waiting for a peripheral, the context of this program was stored away, and the second program in memory was given a chance to run. The process continued until all programs finished running.<ref>{{cite book|url=http://settle.ddns.net/LeoMan/Vol4P1.htm|title=MASTER PROGRAME AND PROGRAMME TRIALS SYSTEM PART 1 MASTER PROGRAMME SPECIFICATION|at=section 6 "PRIORITY CONTROL ROUTINES"|date=February 1965}}</ref>

Multiprogramming gives no guarantee that a program will run in a timely manner. Indeed, the first program may very well run for hours without needing access to a peripheral. As there were no users waiting at an interactive terminal, this was no problem: users handed in a deck of punched cards to an operator, and came back a few hours later for printed results. Multiprogramming greatly reduced wait times when multiple batches were being processed.<ref>{{Cite web|url=https://pediaa.com/what-is-the-difference-between-batch-processing-and-multiprogramming/|title=What is the Difference Between Batch Processing and Multiprogramming|last=Lithmee|date=2019-05-20|website=Pediaa.Com|language=en-US|access-date=2020-04-14}}</ref><ref>{{Cite web|url=https://www.notesjam.com/2017/09/evolution-of-operating-system.html|title=Evolution of Operating System|date=2017-09-29|access-date=2020-04-14}}</ref>