Rich Alderson <RichA at livingcomputers.org> writes:
The 5 characters per word is irrelevant to a
discussion of tape, whether
9- or 7-track: That's how ASCII text was represented in memory, on disk,
on DECtape, or on any other word-oriented medium. Representing the bits
in an ASCII character by the character itself (to make divisions on the
tape more clear), this appears diagrammatically as follows:
Text: HELLOworld
Memory:
HHHHHHHEEEEEEELLLLLLLLLLLLLLOOOOOOO_wwwwwwwooooooorrrrrrrlllllllddddddd_
Core Dump: High Density: SIXBIT: (7 track)
HHHHHHHE HHHHHHHE HHHHHH
EEEEEELL EEEEEELL HEEEEE
LLLLLLLL LLLLLLLL EELLLL
LLLLOOOO LLLLOOOO LLLLLL
....OOO_ OOO_wwww LLLLOO
wwwwwwwo wwwooooo OOOOO_
oooooorr oorrrrrr wwwwww
rrrrrlll rlllllll wooooo
lllldddd ddddddd_ oorrrr
....ddd_ rrrlll
lllldd
ddddd_
Let's add ANSI-ASCII:
.HHHHHHH
.EEEEEEE
.LLLLLLL
.LLLLLLL
_OOOOOOO
.wwwwwww
.ooooooo
.rrrrrrr
.lllllll
_ddddddd
The nice property with this format is that ASCII text in 36-bit words
comes out as ASCII text in octets, while also preserving binary 36-bit
data.