A Generic Architecture of Microcomputer Systems (Cont.)
Arithmetic and Logic Unit (ALU)
It is the part of the CPU which performs operations such as addition, subtraction, and multiplication of integers and bit-wise AND, OR, NOT, XOR, and other Boolean operations.
Register
A register is one of a small number of high-speed memory locations in a computer's CPU. Registers differ from ordinary random access memory (RAM) in several respects:
There are only a small number of registers such as 32. A register may be directly addressed with a few bits. In contrast, there are usually millions of words of main memory, requiring at least twenty bits to specify a location.
Registers are fast; typically, two registers can be read and a third written—all in a single cycle. Memory is slower; a single access can require several cycles.
Address Bus
The connections between the CPU and memory which carry the address from/to which the CPU wishes to read or write.
The number of bits of address bus determines the maximum size of memory which the processor can access.
Data Bus
The bus (connections between and within the CPU, memory, and peripherals) is used to carry data.
Memory
Memory directly accessible to the processor includes main memory, cache, and the CPU registers. Secondary storage includes hard drives, magnetic tapes, CD-ROM, DVD drives, floppy disks, punch cards, and paper tapes.
