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20 votes
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What is the difference between CTSS and ITS?

The technical differences are large when compared to the technical similarities. CTSS was built for a modified IBM 7094 system while ITS was built for the DEC PDP-6 (later PDP-10). Both of these ...
Walter Mitty's user avatar
  • 6,158
20 votes

Why was Logo created?

LOGO was intimately tied up with research into educational methods, and in teaching children how to use computers. The project proposal by Seymour Papert mentions "research on children's thinking ...
dave's user avatar
  • 35.7k
17 votes
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What did memory dumps look like on 36-bit machines like PDP-10s?

A PDP-10 dump is primary a plain memory dump stored in a file typed 'DMP'. To get a printout a utility like DUMP or DUMPR must be used. both offer a huge variety of options to configure what to be ...
Raffzahn's user avatar
  • 224k
16 votes
Accepted

How did 36-bit computers format ARPANET packets?

However, at that time, the world had not yet settled on octets. I beg to differ. If you look through brochures and manuals of next to all manufacturers, they tried hard to be IBM compatible at least ...
Raffzahn's user avatar
  • 224k
15 votes
Accepted

What are the differences between the various 36-bit computers from DEC?

What are the differences between these? I'm not that interested in architectural differences, cache sizes, etc. I'm most interested in the differences that could feasibly trip up an assembly language ...
Raffzahn's user avatar
  • 224k
13 votes

How did 36-bit computers format ARPANET packets?

ARPANET isn't the only context in which the world of PDP-10 computing ran into data paths that used octets for framing. Four other contexts come to mind: 9 track magnetic tape, PDP-11 file exchanges,...
Walter Mitty's user avatar
  • 6,158
13 votes
Accepted

What happened to Doug Engelbart's NLS?

Yes, it was sold to Tymshare. The project continued under the name Augment, running on a modified TENEX, called August, on a KA10 computer. It was later ported to TOPS-20 on a KL10. Tymshare also ...
Lars Brinkhoff's user avatar
12 votes
Accepted

How was concurrent programming achieved on the PDP-10?

Short Answer It's done by use of the EXCHange instruction with interrupts disabled. The Long Read The PDP-10 also allows an interrupt to occur part-way through one instruction, so there's no ...
Raffzahn's user avatar
  • 224k
12 votes
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What is the FPD bit on the PDP-10?

The First Part Done bit is used to signal whether a specific part of an instruction (the "first part") is done already or not. It is only set on instructions like ILDB ("Increment and load byte") ...
tofro's user avatar
  • 35k
11 votes
Accepted

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
9 votes

How did 36-bit computers format ARPANET packets?

36-bit computers were used to communicate through channels which were not 36-bit. ARPANET packets are not the only one, paper and magnetic tapes, connections to terminals, ... have also their frame ...
AProgrammer's user avatar
9 votes

Why was Logo created?

According to Wikipedia: Logo, second paragraph fragment The language was conceived to teach concepts of programming related to Lisp and only later to enable what Papert called "body-syntonic ...
Michel Keijzers's user avatar
8 votes

Is there a non-paging ITS for the PDP-6 or PDP-10?

This is a frame from MIT AI film #43. I'm not sure what year it's from, but it seems to be from the PDP-6 era. The code is very similar to old ITS source code, so it's likely this is a tiny fragment ...
Lars Brinkhoff's user avatar
7 votes

Why was Logo created?

Seymour Papert was a developmental psychologist, and in the early days of computers had lots of interesting ideas about how children might be taught using them. His work's online if you're interested. ...
Greenaum's user avatar
  • 410
7 votes

How was the Microsoft PDP-10 8080 emulator developed?

I'm guessing here, but I suspect they started from Intel's own INTERP/8 8008 simulator. This was supplied on tape for PDP-10 as FORTRAN IV source. While I can't find the source of INTERP/8, the manual ...
scruss's user avatar
  • 21.7k
7 votes

Why does PDP-6 Fortran need JSA and JRA?

I think you need to keep the context in mind to understand the decision. The PDP-6 was introduced in 1964. At the time, the number of high level languages in wide use could be counted on one hand with ...
Jerry Coffin's user avatar
  • 4,872
6 votes

What are the differences between the various 36-bit computers from DEC?

This is only a partial answer, and I hesitate to post it because it's going to primarily be a link, but... There are some real, programmer-visible differences between the PDP-6 and the KA10, though ...
patbarron's user avatar
  • 161
6 votes

Did any 16-bit or 36-bit computer instruction set ever include 4x4 or 6x6 bit-matrix operations?

I don't know if it counts as a 16-bit historical computer, but there were a number of 80287 clones. One of them, from IIT, added a F4x4 instruction that operated on the entire FP stack to perform ...
mcleod_ideafix's user avatar
6 votes
Accepted

Why does PDP-6 Fortran need JSA and JRA?

It's not that FORTRAN required those particular instructions, but that they were the sort of instructions that existing FORTRANs tended to use. At the time, calling conventions were somewhat unsettled,...
dave's user avatar
  • 35.7k
5 votes
Accepted

Why do PDP-10 skip instructions also load an AC?

Some examples. Compare memory contents against two bounds: SKIPG A,FOO ;FOO GREATER THAN ZERO? JRST LOSE CAIL A,BAR ;FOO LESS THAN BAR? JRST LOSE A ...
Lars Brinkhoff's user avatar
5 votes
Accepted

PDP-10 effective address calculation

TL;DR: Yes A (calculated) address (from an instruction) is always used to fetch a word (36 Bit), which, if the I bit was set, is interpreted again the same way - thus allowing indefinite addressing ...
Raffzahn's user avatar
  • 224k
5 votes

How was concurrent programming achieved on the PDP-10?

I'm pretty sure that the KA-10 processor, the first of the PDP-10 processors, had a read-pause-write memory cycle that allowed retrieving and altering a memory location in an atomic operation. ...
Walter Mitty's user avatar
  • 6,158
5 votes

Paradigm for (repeated) use of PDP-10 indirect bit

It might be useful in indirect threaded code. This is a contrived example based on my brief 45-years-ago acquaintance with a Snobol4 implementation (Macro Spitbol - Dewar and McCann). Consider that ...
dave's user avatar
  • 35.7k
5 votes

Did any 16-bit or 36-bit computer instruction set ever include 4x4 or 6x6 bit-matrix operations?

I think the big question you have to ask here is: What would such an instruction have been useful for? Single-bit data types don't usually go together with matrix operations. I've looked at some ...
Chromatix's user avatar
  • 16.8k
4 votes

What is the difference between CTSS and ITS?

It's possible to try both CTSS and ITS yourself. Both operating systems run on emulators. As for differences, Tom Knight, one of the ITS creators, wrote: I would actually say that the main ...
Lars Brinkhoff's user avatar
4 votes

What are the differences between the various 36-bit computers from DEC?

For the assembly language programmer, perhaps a KS10 acted like a KL-10 Model B (except for I/O, as mentioned), but FWIW the KS10 was a completely new CPU implementation using 10 of the AMD 2901 bit ...
Aron Insinga's user avatar
4 votes
Accepted

Is there a non-paging ITS for the PDP-6 or PDP-10?

Here's another clue. It seems Gerald Sussman has a printout of ITS from 1967. The[n] he pulled out a printout that he handled as if it were an original Gutenberg bible. It was the original code for ...
Lars Brinkhoff's user avatar
4 votes

Is there a non-paging ITS for the PDP-6 or PDP-10?

Another piece of tantalizing evidence has surfaced. It's an old ITS file called RG; FD 4/1/68. The name obviously suggests a dating, and it's before a pager was installed. The file contents are ...
Lars Brinkhoff's user avatar
4 votes

How was concurrent programming achieved on the PDP-10?

Digital Equipment Corporation designed the hardware for the AOSE (Add One and Skip if Equal) instruction so that NOTHING could interrupt it. Once that instruction started, it finished. Period. It ...
John R. Strohm's user avatar
4 votes

Why do PDP-10 skip instructions also load an AC?

There are two reasons to have this group of instructions actually load the value that you're comparing. The first is that the instruction word has a field that specifies an accumulator anyway, and the ...
Omar and Lorraine's user avatar

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