Instructions & Programs: Crash Course Computer Science #8

software

(computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory

To make a basic, but functional Central Processing Unit - or CPU - you need:

ALU, control unit, some memory, and a clock

1971, Intel released the 4004 processor that supported

46 instructions, shown here. Which was enough to build an entire working computer.

conditional jumps

JUMP IF EQUAL and JUMP IF GREATER.

hardware

The machines, wiring, and other physical components of a computer or other electronic system

JUMP

This causes the program to "jump" to a new location. This is useful if we want to change the order of instructions, or choose to skip some instructions.

Immediate Value

When the CPU sees an instruction that needs something like a JUMP instruction, it knows it must also fetch the address to jump to, which is saved immediately behind the JUMP instruction in memory.

A modern computer processor, like an Intel Core i7,

has thousands of different instructions and instruction variants, ranging from one to fifteen bytes long.

Infinite loops

keep repeating until the program is interrupted

JUMP_NEGATIVE

only jumps the program if the ALU's negative flag is set to true

STORE

saves data into memory location

HALT

tells the computer when to stop processing

Software can do something our hardware could not. The ALU didn't have the functionality

to divide two numbers, instead it's the program we made that gave us that functionality.