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Computer museum: The Varian and its users

Status: public -- Last revision: May 24, 2015

Varian V73

The Varian V73 was the first computer in the Department Computer Science

The users

Th varian could execute 2 or more tasks simultaneously, one (interactive) in foreground and all others in background. In practice this meant that only one user could work. On the door of the computer room there was a reservation scheme.
Every user had its own removable disc pack. This disc pack did protect users against each other (although this was seldom needed). The system was not protected for user errors.

Starting procedure

The Varian had a front panel with switches. Using this one could enter information in memory. To start the machine one had to enter first about 10 instructions (in binary) into memory. Then this program was started and the program read the information (operating system) from disk or tape.
The Varian used core memory, even when the power was switched of this memory did maintain its state. The ten start instructions were stored at high (mostly unused) addresses and unless some program had overwritten these instructions there was seldom need to switch in the start program.

System Generation

System generation started from magnetic tape (basic system) and punched cards (driver for Tektronix). The complete generation started by switching in a small program to read the tape. We mostly started in the morning with three people. If every thing went well, we had a working system on disc around noon. In the afternoon local system modifications where done and with a bit of luck the Varian could be used following night/day.

The most frequent cause of problems was the punched card reader blocking during reading. the only solution was then to restart. Sometimes the loader did not find a module. In that case a symbol table was printed on the teletype . In this symbol table the missing module was marked ?????. Unfortunately the software assumed 80 symbols per line while our Teletype only had 72. When the symbol was in the last column one could only guess.

Indirect addressing

The address range of the Varian was 32 Kword. Only 15 bit addresses were needed for this range. When the highest bit of an address was 1, it meant that the address to which the 15 lowest bits pointed should again be interpreted as an address. This construction could be used when programming linked lists. However when an indirect address did point to itself the processor would keep reading and interpreting the same address forever. When this did happen you had a programming error but the divers and memory cores for this word would warm up and could wear down. Therefore the hardware did implement a (undocumented) feature to stop this loop after 5 steps. (This feature could be found in the hardware diagrams delivered with the system.)


Vortex only had a line oriented editor. One of our first projects was VEDIT (Varian EDITor), a screen oriented editor on the Tektronix memory screen. VEDIT was written partly in assembly language and partly in Fortran.

The first "computer game"

One of the most used programs made for the Varian was Lambik, an electronic pinball game. The game was called Lambik (a comic hero) because Lambik was drawn on every pin. This was one of the first computer graphics programs. Many lunch hours have been spent playing Lambik. When we moved from the Varian to a PDP 11/60, the PDP (with multiple users and Unix) was too slow to play Lambik any more.

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