Alt code
A legacy method for entering characters via numeric keypad.
Last updated
It works by holding the Alt key and typing a number on the numeric keypad.[1] The BIOS interprets the typed number and places the corresponding character at the cursor.[2] On Microsoft operating systems, personal computers with numeric keypads can use the Alt code method to enter characters lacking dedicated keys.[1]
Quick Facts
- Origin system
- IBM PC compatible personal computers from the 1980s
- Original code page
- CP437
- Common alternative code page
- CP850
- Windows oem behavior
- Alt+### generates characters from legacy OEM code pages
- Windows unicode behavior
- Alt+0### produces characters using the Windows code page associated with the current input locale
Facts from the source article.
How it changed
IBM developed the method to place characters that cannot be typed by a keyboard on the screen.[2] Three-digit codes represent OEM codes, while codes with a preceding 0 represent the new ANSI codes.[2] After adopting Windows to Unicode, entering all Unicode characters by the same method was desired but not achieved across all systems.[2] Holding down the Alt key and typing a decimal number on the keypad was a feature of the BIOS on IBM PC compatible computers from the 1980s.[3]
The code was frequently taken as an 8-bit character from the active code page; for the original IBM PC, that code page was CP437.[3] Microsoft kept the original OEM codes while introducing a new set called ANSI, later renamed Windows codes.[2] In applications using the Windows RichEdit control, numbers from 256 up to 65,535 could generate the matching Unicode character.[4]
What the maker and period sources say
The alt-codes.net site states that Alt-Codes can be typed on Microsoft Operating Systems with NumLock on.[2] It notes that Unicode codes cannot be typed using this method.[2] The site explains that characters produced may vary depending on the OEM Code Page setting.[2] The site specifies that the procedure is not applicable for MacOS.[2]
References
- Wikipedia, "Alt code" (CC BY-SA 4.0), which cites: "Alt Codes List of Alt Key Codes Symbols", www.alt-codes.net (we also read that source) en.wikipedia.org
- "Alt Codes List of Alt Key Codes Symbols", www.alt-codes.net. facts only, no text reused. alt-codes.net
- Wikipedia, "Alt code" (CC BY-SA 4.0), which cites: If the entered value exceeds 255, only the remainder after dividing by 256 (i.e., the value modulo 256) was used by the BIOS. For example, 520 is interpreted as (original not read by us) en.wikipedia.org
- Wikipedia, "Alt code" (CC BY-SA 4.0), which cites: If the entered value exceeds 255, only the remainder after dividing by 256 (i.e., the value modulo 256) was used by the BIOS. For example, 520 is interpreted as; Chen, "The history of Alt+number sequences, and why Alt+9731 sometimes gives you a heart and sometimes a snowman", The Old New Thing, 2 July 2024; Walker, "About Rich Edit Controls", Windows App Development, 27 April 2022 (original not read by us) en.wikipedia.org
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Alt code (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Alt code (CC BY-SA 4.0).
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