9 Feb
2010
9 Feb
'10
12:03 p.m.
On 9 Feb 2010 at 14:50, Ethan Dicks wrote:
I've got a pad of those, I think, for an
early-1960s IBM machine (IBM
1401?). They came in a computer correspondence course lesson pack.
The instructions were represented as EBCDIC characters (letters,
numbers, punctuation), and you drew up the program as streams of BCD
entities that would get manually punched onto cards later.
Probably 1401 autocoder. Not EBCDIC--that didn't come along until
S/360. Most likely just plain old "BCD" punch card code.
I used to have a pad labeled "IBM 1620 Absolute Coding System" (they
were the reverse sides of the SPS coding form pages. One column (5
positions) to record the address of the instruction, another for the
opcode (2 positions), and one each (5 positions) for the P- and Q-
address. You coded it up and then punched it, remembering that a
record mark was an 0-8-2 multipunch and a numeric blank was an 8-4.
Add an 11-punch (minus sign) for any flagged digits.
--Chuck