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16

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 from (say, photoelectric reader versus teletype attachment). On the PDP-1 reading 8-channel tape in binary mode from the photoelectric reader, an 18-bit word was ...


12

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 disadvantages - at engineering time you had to make a fixed-for-all-time choice between how long of a vector you could write vs. the persistence time of the phosphor....


11

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 USED TO DEFINE FUNCTIONS. EXAMPLES ARE (DEFUN ONECONS (X) (CONS 1 X)) WHICH IS EQUIVALENT TO (DEFPROP ONECONS (LAMBDA (X) (CONS ...


10

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 1975 memo PDP35, part 5A documents spheres and capabilities: A virtual memory space, any virtual processors (processes) that might be executing inside that ...


8

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 used in 5 to 8 hole versions (special types up to 24 and more), depending on purpose/equipment. 5 hole was 'small' Baudot type tapes, while 6 to 8 hole shared ...


7

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 bit word. Positions 7 and 8 are unpunched and punched respectively when punching. Lines with position 8 unpunched are skipped while reading. Instructions were ...


5

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: There were no of-the-shelf graphic terminals - or (CRT-based) terminals - at all. A terminal was a card punch, a tape punch (and their counterparts) or a typing ...


3

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 spectrometers and so on. It was also used by ITEK for one of the very early CAD systems in 1964, the Electronic Drafting Machine (PDF warning). It could also be used as ...


3

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.


3

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 conditions, and skip if at least one of the conditions is true. With the I bit, you negate the final result, which (using de Morgan's rule) is equivalent to an "...


1

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. Therefore we can probably assume the effect of setting bit 5 is to get you "do not skip on X, skip on not-X". This is guesswork based on a consideration of ...


1

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 of the results of experiments (eg an early machine learning experiment that simulated the way a mouse learns to navigate a maze); it is likely that these ...


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