INFORMATION TECHNOLGY SYSTEMS

Register Specially wired groups of bits found in the CPU used to store memory addresses or contents. These bits are grouped according to the word size of that computer, which can be 1,2, 4 or more bytes in length. These storage locations
differ from those found in main memory in that they have special circuits built into them that allow rapid transfer of their contents to and from various other places in the CPU.

All computers have an instruction execution cycle:

1. Fetch an instruction from memory via the PC, MAR, and MBR

2. Decode the instruction via Control and IR, update PC

3. Get operand if needed via MAR and MBR

4. Perform instruction via Control, ALU, ACC, and other registers as needed

5. Repeat from #1 until all instructions processed.

Each of these steps can be subdivided into smaller elements called micro-instructions that determine which circuits are to be opened and closed. One micro-instruction is performed in the period between one clock pulse and the next. It usually takes
several (4+) clock pulses to complete one machine language instruction such as ADD, LOAD, STORE, etc.

That's it! All the basic functional parts of the CPU are described here. The wiring diagrams can be quite complex depending on the capabilities of the computer, but all CPUs are nothing more than a collection of bits and circuits wired together in complex
ways to perform programs represented in binary machine language, at a rate determined by the beat of the clock circuit.  Memory is used to store programs and required data until needed by the CPU and also to store the results as they are
computed.