11 10 09 08 07 06 05 04 03 02 01 00 ___________________________________ | | | | | | | | | | | | | |__|__|__|__|__|__|__|__|__|__|__|__| | | | word address |
The main memory of a CDC-160 was 4K words, addressed by the 12-bit S register.
11 10 09 08 07 06 05 04 03 02 01 00 ___________________________________ | | | | | | | | | | | | | |__|__|__|__|__|__|__|__|__|__|__|__| | | | program counter |
The program counter specifies the memory address from which the next instruction will be fetched. After an instruction fetch, the program counter is incremented, and branching is accomplished by assignment to the program counter.
11 10 09 08 07 06 05 04 03 02 01 00 ___________________________________ | | | | | | | | | | | | | |__|__|__|__|__|__|__|__|__|__|__|__| | | | accumulator |
All arithmetic and logical operations operate on the accumulator.