Wednesday, 21 March 2018

1970s Computer Adverts... an occasional series

Introducing the Emulator Terminal, it can be an ADM-3A, VT-52 or other terminals. I want one. Now.

Monday, 19 March 2018

IBM 2701 Data Adaptor Unit

Mainframes in the 1960s and 1970s such as the IBM 360 were huge complicated systems which filled rooms. Some even had smaller computers to help them with the amount of information that needed to be sent into them from a number of sources. These computers were known as Front End Processors or Communication Controllers and they handled data communication allowing the mainframe to concentrate on the jobs at hand [1].

The IBM 270x family, of which the 2701 Data Adaptor Unit was a member of, was an early example of communication controller and worked with the IBM 360 and 370. The 2701 "greatly expands the input/output capabilities of the IBM System/360" [2] by helping to interface to and control information flow from peripherals like the IBM 7701 Magnetic Tape Transmission Unit. The IBM 2701 was introduced in 1964 and replaced by the IBM 3704 in 1972.
Public domain image from SDASM Archives

[1] Barry Wilkinson & David Horrocks, Computer Peripherals (Edward Arnold, 1987) p. 281
[2] IBM 2701 Data Adaptor Unit Principles of Operation (IBM, 1965) p. 5

Friday, 16 March 2018

IBM 7070

The IBM 7070 was a mid-range data processing system introduced in 1958. It was IBM's first stored-program computer to use transistors rather than vacuum tubes and the first of a new line of fully transistorised mainframes. The 7070 used around thirty thousand germanium transistors and could perform twenty seven KIPS (thousand instructions per second). The 7070 used machine words consisting of ten digital digits plus a sign. Each digit was encoded by 5-bits. The 7070 used core memory and could store up to around ten thousand words.

Unfortunately the 7070 was incompatible with the models (such as the 705) it was intended to replace. A simulator was needed to run programs written for older computers though the waste of resource and incompatibilities meant the 7070 was a bit of a flop. The later 7080 was said to be fully compatible. Also coming later were the faster 7072 and 7074 in the early 1960s. They were replaced by the highly successful IBM 360 within a few years.
IBM 7074 (Public domain image)

Tuesday, 13 March 2018

Macintosh SE

The Macintosh SE from 1987 was part of the second generation of Macintoshes, coming out at the same time as the Macintosh II. However unlike the Macintosh II the SE was an all-in-one computer like the first Macs. The SE had a number of improvements compared to earlier Macs: for a start it used the new Apple Desktop Bus interface for the keyboard and mouse. ADB would remain the Apple standard for connecting such devices until the iMac and USB in the late 1990s.

The Macintosh SE was also the first compact Mac to have the option of an internal hard drive and had an expansion slot, SE actually stands for System Expansion. The Mac SE was on sale for 3 years, by then Motorola 68000 based computers were becoming a bit outdated and Apple was moving to faster chips.

There were a number of variants. The SE FDHD (as shown below) introduced the Superdrive - basically a 3.5" floppy drive that could read 1.44MB disks. The SE/30 boasted a 68030 CPU.

The Mac SE shown below was the first Mac I ever bought, second hand from a Cash Converters! It did work fine and helped introduce me to the world of Apple in the mid-1990s. I still miss System 6 (a bit!)

Sunday, 11 March 2018

COMAL (Common Algorithmic Language)

COMAL is a programming language first developed in Denmark in 1973 by Borge R. Christensen and Benedict Lofstedt [1]. The language is a structured language and heavily influenced by contemporary popular educational languages including BASIC and Pascal, indeed the developers of COMAL wanted to combine the simplicity of BASIC with the power of Pascal [2].

What made COMAL stand out was that it was available for 8-bit microcomputers in the late 1970s and early 1980s and was one of the few structured languages available for those computers.

COMAL is still used to this day as a teaching language, it was especially popular in Ireland in the 1980s where Apple supplied around five hundred Apple IIs running COMAL-80 to schools. Earlier versions of COMAL had no graphics commands but these were added later on especially to Commodore implementations of the language which included turtle graphics.

Now for some examples of COMAL, if you are familiar with languages like BASIC then COMAL will seem very familiar:



0050 NEXT NO

[1] John Kelly, Foundations in Computer Studies with COMAL (2nd Edition) (Educational Company of Ireland, 1984) p. vii
[2] Borge R. Christensen, Beginning COMAL (Ellis Horwood, 1982) p. 6

Wednesday, 7 March 2018

1970s Computer Adverts... an occasional series

Well this is a good idea. $395 for a printer was indeed "low cost" in 1979 after all.

Tuesday, 6 March 2018

IBM 5100 Portable Computer advert

An advert for IBM's 5100, one of the first portable personal computers, though as it weighed 22.7KG "portable" was maybe a matter of opinion. Interestingly it was the IBM 5100 which the "time traveller" hoax John Titor had come back to the past from 2036 for, as he needed one to debug legacy computer programs.

Sunday, 4 March 2018

The Virtual Keypunch

If you want a taste of "old iron", and classic computing before the days of microcomputers, floppy discs and the like try the Virtual Keypunch. Punched cards (and tape) were an early data storage method with the data being encoded using holes in a piece of card or other material (hence the need of a Keypunch to make the holes!) The holes and absense of them represented binary data.

Programs were encoded using the cards but because each card (if using the IBM 80 column card method) could only hold one line of code then you might need hundreds of cards for a serious program. All the cards had to be in order and there are plenty of tales of chaos caused by people dropping card stacks!

One benefit of this data storage method however was that if you did suffer such a data corruption you could restore it by putting the cards back in order! Corrupted cards (bent for example) could also repunched. By the 1970s computers were moving onto magnetic storage and visual display terminals though you could still find the keypunches and readers well into the 1990s. I remember at university in the early 1990s one room still had an IBM keypunch machine - though it was not in use. We used the far more up to date Volker-Craig terminals to type our programs instead!