CS 120 Lecture Notes - Lecture 13: Arithmetic Logic Unit, Central Processing Unit, Computer Memory
13 Mar 2017
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Document Summary
Given a turing machine with state and system calls, we still need input/output and memory storage to create a computer. There are 3 parts to a computer: central processing unit (cpu, memory (ram, control unit. The cpu contains the arithmetic logic unit (alu), which does all of the math. Word size: the number of bits that the cpu is operating with (typically 32 or 64 bit) Start at 0 until some large number, each number representing a memory location; every location contains a bit pattern (none of them are empty). Address space: the total number of memory locations there are: 32-bit machines have 4 gigabytes of address space. Read is to access memory, and write is to write memory. You cannot change memory directly, you have to change a register that contains some part that you want and rewrite it to memory. In modern computers, the smallest writing size is 8 bits (1 byte).
