4 Column ASCII Table
00 01 10 11 00 01 10 11
--------------------------+--------------------------
NUL SPA @ ` __00000 | DLE 0 P p __10000
SOH ! A a __00001 | DC1 1 Q q __10001
STX " B b __10010 | DC2 2 R r __10010
ETX # C c __00011 | DC3 3 S s __10011
EOT $ D d __00100 | DC4 4 T t __10100
ENQ % E e __00101 | NAK 5 U u __10101
ACK & F f __00110 | SYN 6 V v __10110
BEL ' G g __00111 | ETB 7 W w __10111
BS ( H h __01000 | CAN 8 X x __11000
TAB ) I i __01001 | EM 9 Y y __11001
LF * J j __01010 | SUB : Z z __11010
VT + K k __01011 | ESC ; [ { __11011
FF , L l __01100 | FS < \ | __11100
CR - M m __01101 | GS = ] } __11101
SO . N n __01110 | RS > ^ ~ __11110
SI / O o __01111 | US ? _ DEL __11111Cue card sized four column ASCII table. Really helps explain why they picked the values they did. It enables trivial manipulation for routine operations:
- Lower Case:
val |= 0b0100000 - Upper Case:
val &= 0b1011111 - Toggle Case:
val ^= 0b0100000 - Char → Int:
val &= 0b0001111 - Ctrl Char:
val &= 0b0011111
That last one's why things like Ctrl+D closes the terminal, Ctrl+I tab
completes things, Ctrl-L clears the screen, and you can backspace using
Ctrl+H. If you've seen your editor add ^M to the end of lines that's because
it's the control code representation of CR. Same
goes for ^[ that you may have seen if you've played with
ANSI escape codes.
Obviously these bit operations only work given a fairly narrow set of preconditions but they were
pretty cost effective in their day.
Why is DEL last? Did you notice it's
0b1111111? On a punch tap, if you want to delete a character, you could
punch it out entirely to indicate you deleted the symbol. At least that's what
Wikipedia says. Cool, huh?
If you didn't catch it, Char → Int means you can read
ASCII numbers directly from
their binary form. If you see a 0b011____,
you can just read the digit from the end.