Inside the first personal computer: Kenbak-1

by Bill Detwiler  |  July 20, 2006, 6:39am PDT  |  Image 3 of 15

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

Kenbak Coding Sheet - Image 3 of 15

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Bill Detwiler

About Bill Detwiler

Bill Detwiler is Head Technology Editor of TechRepublic. Previously, he worked as a Support Tech and IT Manager in the social research and energy industries.

Bill Detwiler

Bill Detwiler
Bill Detwiler is Head Technology Editor for TechRepublic. Previously he worked as a Technical Support Associate and Information Technology Manager in the social research and energy industries. Bill is a Microsoft Certified Professional with experience in Windows administration, data management, desktop support, and system security.

Bill Detwiler

Bill Detwiler
Bill Detwiler has nothing to disclose. He doesn't hold investments in the technology companies he covers.
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