The very simplest answer to register - cpu size is that it is the number of wires that carry the cpu instructions or data. This is a slight over simplification but 16 bit cpu's basicaly use 16 wires, 32 bit cpu's use 32 wires, etc When you hear that a computer has 64 bit addressability it means that it has the wiring for 64 "on/off" states carried on the individual wires. These in turn mean that 64 on-off states provide the highest binary number that can be defined by that number of bits. The "word" originally came from the concept of one individual wiring state that transmitted a computer logical concept within a the limits of the cpu's wiring. So a 16 bit computer's word was 16 bits. The wiring of a computer corresponds in all respects to this word size. Every register is 16 bits on a 16 bit computer.
The counter is a register that holds the address of the next executable instruction. This is a binary number that specifies an address in ram (addressability). This counter is incremented by the next fetch cycle. It can also be altered by programming in which the old value is saved (for later restoration) and a new value provided. This is the basis for all branch, perform, and goto instructions in all languages. Assembler does this but requires programmer effort. _______________________________________________ Pgubook-readers mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/pgubook-readers
