Electrologica X1

Early Dutch computer

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 The X1 was a solid state binary computer ("completely transistorized" In 1965, the X1 was superseded by the X8. Electrologica was taken over by Philips a few years later. As a result, conditional execution can be based on tests made some number of lines earlier, rather than being conditional only based on the result of the most recent arithmetic operation. This allowed for compact expression of programs. The following example demonstrates the loading of the value of memory at n into the accumulator A, calling a subroutine (which presumably uses that value in A), and finally setting A to be the absolute value of the number read:

2A n P // copy [n] to A, set condition flag to "yes" if positive
6T fn 0 // call the function at fn, which will return with the condition flag preserved
N 5P AA // if condition flag is "no", copy A to A

The X1 arithmetic operators used binary ones' complement arithmetic.

The X1 included a simple assembler in its read only memory. It has rather basic features: symbolic addresses may be defined, but symbols are only two letters long. Instructions are named by a combination of a digit representing the operation, and a letter designating the register to be operated on, or one or two letters indicating an operation class. For example, "0A" means "add memory content to accumulator A", and "5P" means "set an accumulator to the negative of another accumulator". The normal use of symbolic addresses is to name "paragraphs", i. e., related blocks of code or data. The symbolic addresses would be modified by a "line number" (a numeric offset) and a "page number" (a number in the range 0 to 31). For example, "3 FE 6" is line number 3, page number 6, representing an offset of 195 (6 * 32 + 3) from the start of paragraph FE. This address notation is a peculiarity of the assembler; the hardware addressing simply uses 15 bit addresses.