IBM 1401 Starting by LaFarr Stuart
Last Up date:
2006 November 2
This Web Page started: 2006 November 2
Of the early "Real Computers" (computers that had nothing dependable in
memory when they were powered up) the 1401 was by far the most
elegant.
The 1401 had a Load Button on the console; but there was a
duplicate one on the Card Reader. The Load Buttons were back
illuminated and always "Yellow". Pressing either of these:
- Cleared the first 100 locations of memory
- Read a card into locations 1 through 80
- Started running at location 1
The first 4 characters punched into that card had to be: ,008
because every op-code had to have a Word Mark set. The comma was the
command that set the word mark. See
More about the
1401
and its features. These 4 characters were followed by 3 more characters.
The "set word mark command" could set two word marks. Making this
instruction 7 characters long. Thus, the next instruction was at
location 008. I believe set word mark is the only command that does
not have to have a word mark with the first character following it.
Generally, at least another "set word mark command" followed. In an 80
column card you could get a few instructions and of course another card
read. Incidentally, the card read instruction could be only one
character--the digit 1, but if it were followed by a 3 character
address, it would read and branch to that address. With this the 1401
was off and running.
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