Lloyd Robert Borrett

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Computing

The First Computer Used

In 1975, I took the subject "Computer Science" whilst at Hellyer College in Burnie. It's amazing that Tasmania, the state those of us on mainland Australia often like to ridicule as being backward, was actually a world leader in the introduction of computers into the education curriculum.

DEC PDP-8/E

DEC PDP-8/E
Digital PDP-8/E minicomputer

Back in 1975, most secondary colleges in Tasmania had either a DEC PDP system on campus, or had a terminal connected to the main DEC system in Hobart. At Hellyer College our computer was a DEC PDP-8/E, one of the most popular minicomputers ever made. 12 bit data word, 15 bit addressing, 8K of wide core memory.

DEC core memory
A DEC core memory card

Of course the computer was wont to crash quite frequently. The process to install the BASIC interpreter involved loading a sequence of machine code instructions via the toggles on the front panel and then waiting for a very large roll of paper tape on which the program was stored to be read in. We'd wait patiently for some 30 minutes and then hold our breath as the tape finished being read. If successful a configuration dialog would begin to clatter out on the Teletype. Unfortunately, it often didn't and we had to start the process again!

Teletype ASR-33

Teletype ASR-33
Teletype ASR-33

Our terminal was a Teletype ASR-33, the classic all-around I/O device. Capable of printing a blazing (for its time) 10 characters per second (upper case and symbols only), generating input at the same speed from keyboard or it's built in punched paper tape reader, and punching paper tape for output and storage at the same speed.

We could even start and stop the paper tape reader or punch by command from the host computer which accounted for the "ASR" (Automatic Send & Receive) designation in it's name.

Yes, we stored our programs and read them back in via paper tape! You could tell those doing "Computer Science" easily as they were the ones walking around with a show box or lunch box in which they stored their paper tapes carefully rolled up and secured with an elastic band.

Using the Computer

Time on the DEC PDP-8/E minicomputer was much sought after. Thus we rejoiced when the college obtained a second Teletype terminal. Two of us on the computer at once! Of course the down side was we had to split the 8K of memory between two users. The policy was a 70/30 split.

Of course many of us were already having a lot of trouble trying to fit our more advanced programs in to 8K of memory. To work on such programs meant going through the process of reloading the BASIC interpreter and answering the setup dialogue so as to only have one Teletype. When finished, of course you had to go through the process again so as to leave the system configured the way you found it.

But we were programming! We had access to a computer! And you never forget your first!

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Last modified: Tuesday, 02 June 2009

 


 
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