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16 votes

How were 18-bit instructions encoded in paper tape?

The answer is invariably specific for a particular computer, and indeed may be specific depending on what is doing the reading (say, hardware bootstrap versus software loader, or what it's reading ...
dave's user avatar
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12 votes
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What was the DEC Type 30 vector graphics display used for?

In that era you couldn't afford to build the raster displays that we have now. The RAM for the frame buffer would have been far too expensive. Vector displays were common, even though they had ...
davidbak's user avatar
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11 votes
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When was DEFUN added to Lisp?

From the MIT AI Lab file .INFO.; LISP ARCHIV for Maclisp updates: 3/1/69 JONL THE CURRENT VERSION OF LISP, "LISP 102", HAS THE FOLLOWING AS-YET UNDOCUMENTED FEATURES: 1)"DEFUN" IS AN FSUBR ...
Lars Brinkhoff's user avatar
10 votes
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Documentation for the MIT PDP-1X OS

I believe this is the best place for PDP-1X documentation: http://bitsavers.trailing-edge.com/pdf/mit/rle_pdp1/ (Linking to a mirror because the main bitsavers.org is offline for the moment.) The ...
Lars Brinkhoff's user avatar
8 votes

How were 18-bit instructions encoded in paper tape?

In addition to anotehr-dave's in depth answer maybe some (not PDP-1 specific) background information to show the environment: 8 hole punch tape was only a thing rather late on. Paper tape was commonly ...
Raffzahn's user avatar
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7 votes

How were 18-bit instructions encoded in paper tape?

This is explained here starting at page 21. There are basically two modes in which a paper tape can be used: Alphanumeric: 8 bits per tape line. Binary: 3 tape lines of 6 effective bits each per 18 ...
WimC's user avatar
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5 votes

What was the DEC Type 30 vector graphics display used for?

Just what was it used for? The answer is in the name - to display graphics It doesn't make much sense to produce a list of application, but lets look at the core issue of having a screen at all: ...
Raffzahn's user avatar
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3 votes

What was the DEC Type 30 vector graphics display used for?

The PDP-1 was priced to be sold to a lab and was relatively easy to interface to. This means that it could be used for processing and displaying data from a variety of equipment such as mass ...
hughk's user avatar
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3 votes

When was DEFUN added to Lisp?

The defun macro is just syntactic sugar for define plus lambda. InterLisp (1970) doesn't seem to have it either, so your MacLisp example is either the first, or pretty close to being the first.
Omar and Lorraine's user avatar
3 votes
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PDP-1 skip group invert bit functionality

Is this example equivalent to "skip on not zero accumulator"? Yes. It's the same idea as skips on the PDP-8, as explained in this Q&A: Without the I bit, you "or" the ...
dirkt's user avatar
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1 vote

PDP-1 skip group invert bit functionality

If the normal instruction is "Skip on X, do not skip on not-X" then if setting bit 5 resulted only in "do not skip on X, do not skip on not-X", it would not be very useful. ...
dave's user avatar
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1 vote

What was the DEC Type 30 vector graphics display used for?

The PDP-1 was designed as an unofficial successor to the MIT Lincoln Labs TX-0, which also had a similar display. On the TX-0 this had been used for interactive debugging as well as graphical display ...
occipita's user avatar
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