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The Electrologica X1 was a digital computer designed and manufactured in the Netherlands from 1958 to 1965. About thirty were produced and sold in the Netherlands and abroad.
The X1 was designed by the Mathematical Centre in Amsterdam, an academic organization that had been involved in computer design since 1947, and manufactured by Electrologica NV, a company formed expressly for the purpose of producing the machine.
The X1 was a solid-state binary computer ("completely transistorized") with magnetic core memory. Word-length was 27 bits and peripherals included punched and magnetic tape. It was one of the first European computers to have an interrupt facility.
Like its counterparts the Zuse Z22 and the ZEBRA, (and the much later ARM architecture), all instructions, not just branches, could be made conditional. This allowed for compact expression of programs. The following example demonstrates the loading of the absolute value of memory at n into the accumulator A:
2A n P // copy [n] to A N 3A n // if A is negative, copy -[n] to A
The X1 arithmetic operators used binary fixed-point arithmetic.
A notable peculiarity of the X1, or at least of the people who worked with it, was the use of base-32 notation when writing addresses.
The X1 was the subject of Edsger Dijkstra's Ph.D. dissertation, and the target of the first complete working ALGOL 60 compiler, completed by Dijkstra and Jaap Zonneveld. In 1965, the X1 was superseded by the X8. Electrologica was taken over by Philips a few years later.
- CACM 2(9): 24 (1959). 1, EE, Edsger W. Dijkstra: Communication with an Automatic Computer, University of Amsterdam 1959.
- The Electrologica X1 and X8 computers
- "Communication with an Automatic Computer", Dijkstra's Ph.D. thesis (PDF)
- The Dijkstra-Zonneveld ALGOL 60 compiler for the Electrologica X1 (PDF) includes a good description of the X1 instruction set.