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> Now that I think about it, its surprising ASCII wasn't designed around ease of translation to segmented display. Wikipedia has a section on the design consid

by kibwen 4y ago

> Now that I think about it, its surprising ASCII wasn't designed around ease of translation to segmented display. Wikipedia has a section on the design considerations of ASCII: https://en.wikipedia.org/wiki/ASCII#Design_considerations https://en.wikipedia.org/wiki/ASCII#Design_considerations

jodrellblank 4y ago
I love that there's a fractal world down there; from that the digits 0-9 start with bit pattern 0011 and then their value in binary to make easy convertion to/from BCD, and that control codes Start Message and End Message were positioned to maximise the Hamming distance so they're maximally different and least likely to be misinterpreted as each other in case of bits being mixed up, that 7-bit ASCII used on 8-bit tape drives left room for a parity bit for each character, that lowercase and uppercase letters differ only by the toggling of a single bit, that some of the digit/shift-symbol pairings date back to the first typewriter with a shift key in 1878...
- jasomill 4y ago
  And my personal favorite: DEL is 1111111 so it could be punched over any other character to "delete" it from a paper tape.
  - IIAOPSW 4y ago
    In the 8 bit variant you could also interpret it as the Morse Code letter ........, which is an early form of non-printable character known as a "procedure sign" (aka "pro-sign"), and is often transcribed as letters without the inter-letter spacing (Eg <SOS> is the transcription of ...---...). The prosign <eeeeeeee> means the sender has mis-keyed something and you should ignore the previous character.
kps 4y ago
The Wikipedia section is pretty good now. There are a few notable omissions. The backslash was added so that logical ∧ and ∨ could be written as /\ and \/ — two operators for the price of one. The characters : and ; were considered the least important punctuation, so they were placed immediately after 9, where they could be replaced by single-character 10 and 11 for shillings. And the characters *+,-./ were placed in rows 10-15 so that they could easily be combined with the digits to make a 16-bit subset suitable for writing numbers and basic arithmetic.

by kibwen 4y ago

jodrellblank 4y ago

I love that there's a fractal world down there; from that the digits 0-9 start with bit pattern 0011 and then their value in binary to make easy convertion to/from BCD, and that control codes Start Message and End Message were positioned to maximise the Hamming distance so they're maximally different and least likely to be misinterpreted as each other in case of bits being mixed up, that 7-bit ASCII used on 8-bit tape drives left room for a parity bit for each character, that lowercase and uppercase letters differ only by the toggling of a single bit, that some of the digit/shift-symbol pairings date back to the first typewriter with a shift key in 1878...

jasomill 4y ago
And my personal favorite: DEL is 1111111 so it could be punched over any other character to "delete" it from a paper tape.
- IIAOPSW 4y ago
  In the 8 bit variant you could also interpret it as the Morse Code letter ........, which is an early form of non-printable character known as a "procedure sign" (aka "pro-sign"), and is often transcribed as letters without the inter-letter spacing (Eg <SOS> is the transcription of ...---...). The prosign <eeeeeeee> means the sender has mis-keyed something and you should ignore the previous character.

kps 4y ago

The Wikipedia section is pretty good now. There are a few notable omissions. The backslash was added so that logical ∧ and ∨ could be written as /\ and \/ — two operators for the price of one. The characters : and ; were considered the least important punctuation, so they were placed immediately after 9, where they could be replaced by single-character 10 and 11 for shillings. And the characters *+,-./ were placed in rows 10-15 so that they could easily be combined with the digits to make a 16-bit subset suitable for writing numbers and basic arithmetic.