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

About Bill Detwiler

Bill Detwiler is Managing Editor of TechRepublic and Tech Pro Research and the host of Cracking Open, CNET and TechRepublic's popular online show. Prior to joining TechRepublic in 2000, Bill was an IT manager, database administrator, and desktop supp...

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