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38 votes
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What was the rationale behind 32-bit computer architectures?

there some particular design theory or constraint that made a 32-bit word size attractive for IBM to migrate to? It all comes down to the most basic data type, addressing constrains and, less ...
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35 votes
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Were any IBM mainframes ever run multiuser?

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 ...
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21 votes

Were any IBM mainframes ever run multiuser?

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 ...
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19 votes

Were any IBM mainframes ever run multiuser?

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 ...
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19 votes

When did IBM start to use ASCII?

IBM started using ASCII before 1970; the 2260 terminal, released in 1964, used the unpublished (but ratified) 1965 version of the ASA X3.4 standard. IBM mainframes still use EBCDIC, so I don’t think ...
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19 votes
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When did IBM start to use ASCII?

TL;DR: ASCII was never intended for processing, just as an interface standard for data exchange (hence the name American Standard Code for Information Interchange) IBM never switched, it still uses ...
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11 votes
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Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers These issues are unrelated. Registers are about addressing, so they need to hold an address word. Byte addressable ...
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11 votes

Why did IBM skip "System/380" as a mainframe family name?

If you have a look at the announcements for the various System/XXX machines you mention, you'll notice a pattern: System/360, April 1964. System/370, June 1970. System/390, September 1990. Comments ...
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10 votes
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Why did IBM 7030 or IBM 360 use byte and word addressing simultaneously

[Please see as well this answer, as it's kind of an extension] Why did IBM 7030 or IBM 360 use byte and word addressing simultaneously Not sure what's with /360 reference here, as it's uses byte ...
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10 votes

Were any IBM mainframes ever run multiuser?

But were any of them used like the college-lab VAX, to provide a bunch of people with interactive shell accounts that could run arbitrary code? Absolutely 100%! TL;DR University of Maryland - ...
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10 votes

Were any IBM mainframes ever run multiuser?

Certainly. A place where I worked in the early 1980s had an IBM 4341 system running some species of MVS, with the TSO ('time sharing option') that supported interactive program development. I'm ...
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8 votes

How was the APL character set represented on IBM mainframes?

It's important to keep in mind, that there weren't that much symbols using overstrike in basic (IBM) APL. By using an 8 bit codeset they all could be integrated. The most common charset on the ...
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8 votes

Were any IBM mainframes ever run multiuser?

Thus it was necessary or at least highly beneficial for the operating system to use memory protection to screen the users from each other ... That "memory protection" scheme is typically ...
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7 votes
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Weird example code for CALL/360:BASIC

So... it just errors out and never closes the file? So why is there a line 70? Left over from the previous program? Is there unexplained magic here that causes it to continue after 60, or is this as ...
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6 votes

Were any IBM mainframes ever run multiuser?

Circa 1970, MIT's EE department operated an APL\360 virtual machine under CP/67 on an IBM 360/67. APL\360 was a multiuser dialup system for 360 mainframes, specialized for APL, but virtualizing it ...
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  • 973
6 votes

Were there "higher level programming" macro packages for the IBM Macro Assembler?

The IBM/360 Macro Assembly language was quite powerful, allowing non-trivial compile-time string manipulation. Well, reducing it to "string manipulation" might fall short, as there is no ...
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6 votes

Why did IBM System /360 have byte addressable RAM, but didn't have 8 bits registers

There is no downside I can see to storing an 8-bit quantity in a 32-bit register if you already have the 32-bit register. Load/store take the same amount of time. Memory transfers are at least word-...
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  • 27.8k
6 votes

Why did IBM 7030 or IBM 360 use byte and word addressing simultaneously

'Byte' was used before it meant '8 bits' and It was used on machines that had word-addressable memory. The point was for the program to be able to read and write data of less than a word size. The ...
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  • 27.8k
6 votes

Were any IBM mainframes ever run multiuser?

The University of Cambridge (UK) Computing Service acquired a 370 around 1972 at the time I was starting my Ph.D, and operated it as a time-sharing service. Using experience from the Titan operating ...
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6 votes

What was the rationale behind 32-bit computer architectures?

One small reason is that you can access memory as a bit array without needing to divide (or do a modulo). Just use the bottom N bits for the byte or word or data cache line position or shift, and the ...
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  • 7,684
5 votes

How was the APL character set represented on IBM mainframes?

IBM had several different APL mainframe implementations, and they where updated and modified over many years to support different types of hardware and I/O equipment over their life time. The source ...
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5 votes

Were any IBM mainframes ever run multiuser?

Wikipedia has this: https://en.wikipedia.org/wiki/Time-sharing_system_evolution IBM features heavily.
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  • 275
5 votes

Were any IBM mainframes ever run multiuser?

To add to all this, System/370 with virtual memory was one of the first platforms (perhaps the third) that UNIX was ported to. You can read a paper about that porting done here. IBM would follow it ...
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  • 9,396
5 votes

Were any IBM mainframes ever run multiuser?

In the 70's I used Orvyl and Wylbur extensively on Stanford's 360/67, which Wikipedia says were originally developed in 1967-68. There were golfball terminals all over campus. Keypunched batch jobs ...
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5 votes

What was the rationale behind 32-bit computer architectures?

Worthy of mention is the rise of the microprocessor- notably the 4004 which was designed for mostly numerical operation in calculators. Whether the step to 8 bit architecture was inevitable is open ...
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4 votes

Were any IBM mainframes ever run multiuser?

Yes To add to the UM students above we had a 7090 in the mid 60s that any student could run their own program on by submitting a punch card deck to the computer center. You picked up the print out and ...
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  • 41
4 votes

How was the APL character set represented on IBM mainframes?

I was once writing an APL compiler (never finished, having figured I could single-handedly write a compiler in a 10 week undergraduate programming project), and the choice I made was to have an ...
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  • 27.8k
4 votes

When did IBM start to use ASCII?

In the 1960s, IBM used a crazy variety of character codes. IBM was the king of punched cards, commonly known as "IBM cards", so many codes related to the sparse 12 bit codes used for those. ...
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  • 973
3 votes

Any informations on IBM's "Generalized Information System" still available?

All I could find on IBM's website was the following quote: One of the earliest systems designed to provide structure and random access to data was the Generalized Information System (GIS), which was ...
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3 votes

Were any IBM mainframes ever run multiuser?

Yes, I had a timeshare account on my university's IBM System/360 in the early 1970s where I wrote and debugged programs in APL. The computer center had several dumb terminals that students could use ...
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