Computer - Revision history

Jnc: /* See also */ +List of Computers - de-orphanize

2024-02-24T16:05:10Z

‎See also: +List of Computers - de-orphanize

Jnc: grammar

2023-12-10T02:19:38Z

grammar

Vaxorcist: /* External links */ Fixed typo

2023-12-09T18:18:11Z

‎External links: Fixed typo

Jnc: Stop trying to cram this into Computing device

2023-12-07T12:56:21Z

Stop trying to cram this into Computing device

New page

A '''computer''' is unfortunately not defined in a way that is both generally agreed, and precise. (Which leads to ferocious debates about what was the first 'computer' - because, as Michael Williams observed, "If you add enough adjectives to a description you can always claim [a particular machine to be the 'first'].")

The meaning of 'computer' is generally now 'stored-program computing device' - i.e. the [[program]] (which, it must be emphasized, is a specified series of elementary steps) is stored in the device in some form, in a way that the user can relatively easily change to make it perform some other computation; '''programmability''' is not simply the ability to make physical changes to the device to change what calculation it performs - even if those changes are instantiated in something that was added to the device for that exact purpose, like the [[plug-board]]s of the [[ENIAC]].

An open question is whether the program must be stored in [[memory]] that the computer can modify, allowing the program to change its own program if it desires. This has historically been seen as part of what makes a 'computer', both because [[Turing machine]]s (the theoretical foundation of computers) had that capability, and because the first [[electronic]] computers generally could do that too; they used the same memory to hold the program and data.

Whether or not the ability to modify its own program is important, for something to be classified as a 'computer', can be debated; modern computers almost always run [[pure code]] (in part because [[self-modifying code]] can be difficult to understand and [[debug]]), so it is probably not critical; indeed, [[embedded system]]s usually use [[read-only memory|ROM]] for their program storage. On the other hand, program modifiability is a key aspect of classical Turing machines; but it might be possible for a machine running out of ROM to [[emulator|emulate]] a Turing machine, thereby making such a machine a Turing machine (since it can provide a Turing machine). It is also possible that having the ability to do [[conditional branch]]es could be an alternative to being able to modify the program, for [[Turing complete]]ness.

==See also==

* [[Computing device]]
* [[Harvard architecture]]

==Further reading==

* Paul E. Ceruzzi, [https://ed-thelen.org/comp-hist/Reckoners.html ''Reckoners: The Prehistory of The Digital Computer, From Relays to the Stored Program Concept, 1935-1945''], Greenwood, Westport, 1983
* William Aspray (editor), [https://ed-thelen.org/comp-hist/CBC.html ''Computing Before Computers''], Iowa State University Press, Ames, 1990
* Brian Randell (editor), [https://link.springer.com/book/10.1007/978-3-642-96145-8 ''The Origins of Digital Computers: Selected Papers''], Springer-Verlag, Berlin, Heidelberg, New York, 1973, 1982 (3rd edition)
* Nicholas Metropolis, Jack Howlett, Gian-Carlo Rota (editors), [https://www.sciencedirect.com/book/9780124916500/a-history-of-computing-in-the-twentieth-century ''A History of Computing in the Twentieth Century''], Academic Press, New York, 1980
* Raúl Rojas, Ulf Hashagen (editors), ''The First Computers: History and Architectures'', MIT Press, Cambridge, 2002

==External links==

* [https://www.gleech.org/first-computers Disambiguating the first computer]
* [http://www.inf.fu-berlin.de/inst/ag-ki/rojas_home/documents/1997/Universal_Computer.pdf How to Make Zuse's Z3 a Universal Computer] - it tuns out one doesn't even need conditional branching to have a UTM

[[Category: Basics]]

@@ Line 11: / Line 11: @@
 * [[Computing device]]
 * [[Harvard architecture]]
 ==Further reading==

@@ Line 3: / Line 3: @@
 The meaning of 'computer' is generally now 'stored-program computing device' - i.e. the [[program]] (which, it must be emphasized, is a specified series of elementary steps) is stored in the device in some form, in a way that the user can relatively easily change to make it perform some other computation; '''programmability''' is not simply the ability to make physical changes to the device to change what calculation it performs - even if those changes are instantiated in something that was added to the device for that exact purpose, like the [[plug-board]]s of the [[ENIAC]].
-An open question is whether the program must be stored in [[memory]] that the computer can modify, allowing the program to change its own program if it desires. This has historically been seen as part of what makes a 'computer', both because [[Turing machine]]s (the theoretical foundation of computers) had that capability, and because the first [[electronic]] computers generally could do that too; they used the same memory to hold the program and data.
+An open question is whether the program must be stored in [[memory]] that the computer can modify, allowing the program to change itself if it desires. This has historically been seen as part of what makes a 'computer', both because [[Turing machine]]s (the theoretical foundation of computers) had that capability, and because the first [[electronic]] computers generally could do that too; they used the same memory to hold the program and data.
 Whether or not the ability to modify its own program is important, for something to be classified as a 'computer', can be debated; modern computers almost always run [[pure code]] (in part because [[self-modifying code]] can be difficult to understand and [[debug]]), so it is probably not critical; indeed, [[embedded system]]s usually use [[read-only memory|ROM]] for their program storage. On the other hand, program modifiability is a key aspect of classical Turing machines; but it might be possible for a machine running out of ROM to [[emulator|emulate]] a Turing machine, thereby making such a machine a Turing machine (since it can provide a Turing machine). It is also possible that having the ability to do [[conditional branch]]es could be an alternative to being able to modify the program, for [[Turing complete]]ness.

@@ Line 23: / Line 23: @@
 * [https://www.gleech.org/first-computers Disambiguating the first computer]
-* [http://www.inf.fu-berlin.de/inst/ag-ki/rojas_home/documents/1997/Universal_Computer.pdf How to Make Zuse's Z3 a Universal Computer] - it tuns out one doesn't even need conditional branching to have a UTM
+* [http://www.inf.fu-berlin.de/inst/ag-ki/rojas_home/documents/1997/Universal_Computer.pdf How to Make Zuse's Z3 a Universal Computer] - it turns out one doesn't even need conditional branching to have a UTM
 [[Category: Basics]]