U.S.A. Standard Code for Information Interchange
approved by the United States of America Standards Institute
Also known as:
ISO 646-US-1972 -- there is one notable difference: vertical bar instead of broken vertical bar
ISO 646-IRV-1991 -- capitalist forces displace ISO 646-IRV-1972 with ISO 646-US-1972, establishing the new International Reference Version of ISO 646-IRV-1991. BFD.
This is a 7-bit character set. Holding a 7-bit character in a 8-bit byte is easy. What to do with that extra bit? Well, it's been used as an even parity bit, an odd parity bit, and as extensions to the glyph characters.
IBM in their code page 437 (IBM CP437, also known as OEM437) used the control characters and high-bit range for additional glyphs. Sometimes to get them on the display, the programmer had to use either some low level helper routines (interrupt calls), or change the bytes on the video card text page by setting the bytes directly.
Apple II's used the extra bit to indicate whether the text was inverse (or blinking) or not. With the Apple IIgs, Apple included extra interesting glyphs in those ranges.
Commodore's PET, VIC, and CBM personal computers used the extra bit for their own interesting glyphs. Like IBM, they also included glyphs in the control character range.
Other standards are supersets of X3.4-1967, or a close variant such as ISO 646-US-1972. Such standards like ISO 8859 family of character sets. Or "de facto" proprietary standards like Apple's MacRoman (extended ISO 646-US-1972) or Microsoft's Win1252 (extended ISO 8859-1).
Some computers actually use the standards as is: most Unix OS, Amiga OS, Linux OS.
The current standard that's worthy of compliance, in my humble opinion, is ISO 10646 commonly known as [Unicode], currently at v3.0 with v3.1 in beta (as of this writing, 2001-Jan-17). Using UTF-8 encoding of UCS-4 (31-bit universal character set).
Newline sequence: 0A (LF)
CP/M and Microsoft DOS and Windows idiosyncratically uses: 0D 0A (CR LF)
Apple's AppleDOS, ProDOS, GS/OS and MacOS idiosyncratically uses: 0D (CR)
Unix, AmigaOS, Linux, and many other OS's use the standard's specification.
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0
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NUL | DLE | SP |
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1
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SOH | DC1 |
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2
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STX | DC2 |
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3
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ETX | DC3 |
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4
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EOT | DC4 |
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5
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ENQ | NAK |
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6
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ACK | SYN |
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7
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BEL | ETB |
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8
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BS | CAN |
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9
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HT | EM |
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A
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LF | SUB |
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B
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VT | ESC |
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C
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FF | FS |
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D
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CR | GS |
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E
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SO | RS |
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F
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SI | US |
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DEL |
Legend
| light blue background indicates a control character | |
| normal colored background indicates a glyph (printable) character | |
| NUL | null |
| SOH | start of heading |
| STX | start of text |
| ETX | end of text |
| EOT | end of transmission |
| ENQ | enquiry |
| ACK | acknowledge |
| BEL | bell (audible or attention signal) |
| BS | backspace |
| HT | horizontal tabulation |
| LF | line feed |
| VT | vertical tabulation |
| FF | form feed |
| CR | carriage return |
| SO | shift out |
| SI | shift in |
| DLE | data link escape |
| DC1 | device control 1 (XON) |
| DC2 | device control 2 |
| DC3 | device control 3 (XOFF) |
| DC4 | device control 4 |
| NAK | negative acknowledge |
| SYN | synchronous idle |
| ETB | end of transmission block |
| CAN | cancel |
| EM | end of medium |
| SUB | substitute |
| ESC | escape |
| FS | file separator |
| GS | group separator |
| RS | record separator |
| US | unit separator |
| SP | space (normally whitespace glyph) |
| ' | apostrophe |
| , | comma |
| < | less than |
| > | greater than |
| \ | reverse slant |
| ¦ | broken vertical bar, Latin1 and Unicode: ¦ (¦) |
| DEL | delete |
Even Parity Grid (1 even parity bit + 7 data bits)
| hexadecimal |
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0 |
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F |
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