73
And if you go back further, e.g. to the ENIAC, you'll see a word size of 40 bits.
And if you go back even further, to mechanical calculators, you'll see word sizes determined by the number of decimal digits they can represent.
And that explains the approach: Computers originally were meant to automate calculations. So you want to represent numbers. With ...
68
In the 1980's a certain bank with its headquarters in Edinburgh has a problem with (IBM) disc storage that had to be kept online for live customer account information for branch and ATM machine operation that it ran out of city buildings to put the disc drives in.
Yes: Not just a building, but buildings. Luckily, just after that time radical developments ...
53
Old COBOL standards were based around 80-column punched cards, and columns beyond 71 (or 72) were reserved for line numbers. They were little used, but a numbered deck, if dropped, could be sorted by a collator.
Because of this, some compilers would not parse beyond a certain column (which could be 70, 71, or 72). So, in the interests of compatibility, it ...
51
DOS/360
(As distinct from TOS/360, the tape OS)
Announced at the end of 1964 per Wikipedia.
50
TL;DR;
Punch card code is not binary but a collection of n out of m encodings.
Long Story
Yes, really a long story, so I'll only cover the main line from Hollerith to EBCDIC. There are many sidelines for special equipment, situations and as used by different manufacturers. Some covering up to 7 holes but all mostly compatible in the basic Numeric/Alpha ...
36
Yes, huge safety concerns as I remember engineers sitting inside the cabinets of large mainframes while it was running, fully powered, large currents in each cabinet powering fans. Cooling water being pumped through the frames. Huge wiring looms hanging across the floor to great logic analysers on wheeled trolleys; trip hazards.
One person regularly smoked ...
33
Yes. There were CP/CMS and VM/370 - true multiuser operating systems running on the mainframe with individual users logged in. AFAIK it was mainly used for software developers (to develop IBM mainframe software).
I had the pleasure working on VM/370 once. Not what you'd call an ideal development environment. You got storage allocated to you: A certain ...
31
Uppercase text only needs six bits per character.
The fundamental mistake that you are making is assuming that punch codes were binary numbers.
They were not.
The encodings were patterns, combinations of of zero, one, two, or three holes.
This is a reference card in IBM 5081 format:
The row numbering was somewhat odd, for historical reasons: 12, 11, 0, 1, ...
30
But I can't seem to find any pictures of a computer filling an entire room, much less a whole multi-story building.
(Image taken form Centre for Computing History)
Well, for example look at this picture of a 4341 setup. This is a small entry-level mainframe of ~1980. With a believable setup for such small machine with:
CPU (in the middle against the 'wall'...
30
Although you have many correct answers describing the nature of the coding used in punched cards, no one has touched on the mechanical properties of the cards. Regular users of punched cards in the past would be familiar with this issue, as getting cards through the mechanics of a fast card reader regularly and repeatedly was a major issue at the time.
If a ...
21
The excellent history book "AN/FSQ-7: the computer that shaped the Cold War" describes the size of a 1950's era radar monitoring air defence computer.
A single installation (a single computer) was built in a specially designed four-storey "blockhouse" - 74 feet high and providing 90,000 square feet of floorspace. A separate building housed the generators ...
20
Here's a picture of the "Strela" (arrow) computer (1954)
Vacuum tubes, 2000 op/sec (on 43-bit fixed point), 150kWt, 300 m³
20
Longer words mean more bits can be processed at once. An 8 bit processor can perform a 32 bit calculation, but it has to do it in 4 stages of 8 bits each. A 32 bit processor can do it in one stage.
Since early computers had limited clock speeds due to slow electronics increasing the word size was one of the few options available to improve performance.
In ...
19
There is some code left over in the pcc codebase showing how the GCOS compiler (for the Honeywell/GE 6000 series) worked, it used 9-bit (ASCII, most likely) characters natively, but supported 6-bit BCD characters with `STRING` syntax for encoding them in the source.
The lexer support for these string tokens can be seen at old/pcc/mip/scan.c, the strtob ...
19
IBM mainframes are still around (IBM Z). Linux has been available for IBM Z hardware and its predecessor, System/390, for 20 years, and z/OS is itself a certified UNIX through the z/OS UNIX System Services. Which is to say that IBM mainframes have been run in UNIX-like multi-user fashion for two decades by running UNIX.
Apart from that, z/OS and its ...
18
What is the purpose of the yellow wired panels
It's the backplane, simply the wiring of the machine.
on the IBM 360 Model 20?
Not just there, but next to every mainframe was made that way. Depending on planned (and ordered) production run some would get printed boards, but usually all wiring was done as wire-wrap. The -20 was sold in quite high numbers ...
18
It starts with discussion about computers overheating,
That discussion seams to include some quite vague memory, so I wouldn't put to much into here. Still, such buttons were available and even installed after market, depending on company or state regulations. A CRAY Y-MP EL used at TU München is a great example, with its big power off:
(Picture taken from ...
17
In the old days, I remember we were told to never go beyond the 70'th column in the text editor (the actual value was usually something above 70, but less than 80). [...] If it makes a difference, this was when programming COBOL.
No, it doesn't, as it was more of a feature of the underlaying priciples and standards for handling punch cards. By default ...
17
On the basis that a picture is worth a thousand words, I include my scan of a punched card:
As amply described in the other answers, it shows how the columns are visibly marked on the card for different purposes. It makes sense when you see a card. It makes less sense when you're using a computer display or are using paper tape!
17
The main computer hall of the company I worked for in the 1970s and 1980s was about half the size of a soccer pitch - about 200 feet by 150 feet. That contained three IBM S/370 mainframes at one end, and the rest of the room was packed full of disk drives, stacked up to 6 or 7 feet high with narrow walkways between, with the outside walls lined with tape ...
17
TL;DR:
Which components or facilities were the biggest obstacle to porting typical COBOL applications?
Simply that there were not many applications that made sense to be ported to (desktop) micros. If at all, downward migration of whole applications was toward /3x systems and ultimately AS400. Which was well supported and rather painless.
<RANT>
...
15
Here's the computer room of the Shuttle Mission Simulator (SMS), building 5 of NASA's Johnson Space Center, in the early 1980s. Most of the boxes are parts of a Sperry-Univac 1100 mainframe, but some are "intelligent controller" satellite computers, Perkin-Elmer 8/32s. There are also some Singer-Link Flight Simulation proprietary visual system cabinets and ...
15
Another one to mention is MTS which was first released in 1967, last release in 1988. It was in use at Rensselaer Polytechnic Institute from 1976 to 1999, of which I took part during the early 80s. In 1984 they were running it on Sybil, a dual processor IBM 3081D; slightly before that it ran on Myron, which I think was a 3070 but I'm not sure.
There were a ...
14
It seems to me that a smart terminal would need a microprocessor, so I would expect them to start showing up in the early seventies,
Not really, as discrete, specialized processors could do the job even before that.
When did they arrive on the scene?
TL;DR: Gradually between 1964 and 1971
As with every 'first' question, the answer is rather vague and ...
14
I found the explanation in chapters 23 and 20 of Mackenzie, Charles E, Coded Character Sets, History and Development (Addison-Wesley, 1980), which was linked in a footnote to Wikipedia's ASCII article.
In the early 1960s, 7-bit ASCII was being standardized as an communication format (the last I in the name comes from "interchange"), but this does not ...
13
@raffzahn describes object files, which are not executable. They need to be read into the linkage editor, which produces a load module. That is what CSV (the newer name of the component that loads modules and relocates addresses) loads, and then the operating system eventually branches to the entry point (not always the first byte).
What you are looking for ...
13
A possible answer occurs to me: it might be precisely because of the slow memory.
Say you want to add a pair of ten-digit decimal numbers, SUM += VAL, on a 6502. That chip has a BCD mode in which it can add two digits at a time; it has to do everything through an 8-bit accumulator. So we need a loop of five iterations, which we might unroll for speed. Each ...
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