# Input / Output Subsystem
Handles devices that allow the computer system to:

* Communicate and interact with the outside world
	- Screen, keyboard, printer

* Store information

![[io-subsystem.png]]

# The Control unit
Program stored in memory. (machine language in binary)

Task of control unit is to execute programs by:
* Fetch: from memory the next instruction
* Decode: instruction to determine what to do
* Execute: issuing signals to ALU, memory and IO systems.

Repeats until HALT instruction.

# Typical Machine Instructions
MOV: move data from a to b
ADD: add numbers
SUB: subtract numbers
JMP: transfers program control flow to the indicated instruction