Inside the first personal computer: Kenbak-1

Kenbak Coding Sheet

This sheet (the Kenbak Coding Sheet) tells just about all there is to know about the Kenbak-1.

There were three programming registers, A (location 000), B (001), and X (002) which were assigned locations in the memory. The X register was for memory indexing but could be used in any way you liked. The program counter was P and it was memory location 003. The lights displayed the contents of location 200. Input was made to 377. Operations that could be performed on A, B, and X were Addition, Subtraction, Load, Store, Logical Or, Logical And, Load Negative. The addressing modes were Immediate, Memory, Indirect, Indexed, and Indirect/Indexed. One could do things like subtract the contents of A from A which yielded Clear A.

Reprinted with permission from Vintage-Computer.com


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