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CSCI 260 - Professor Pavel

What is a program?

List of instructions for computer to execute.

What is purpose of computer?

To execute program.

What does it mean to run the program?

Execute program one by one line.

What computer component executes program?

The CPU runs lines of program one by one.

What is data?

Whatever isn’t instructions, is data.

Where is running program stored? What else is stored?

Stored in the RAM also called main memory (code and data).

Machine Cycle

A sequence of steps that CPU goes through to execute a single instruction.

Machine Cycle Steps

Fetch: CPU fetches instruciton from RAM

Decode: Prepare instruction execution

Execute: Do what instrument says

Write-back: Some instructions require results to go back to CPU.

What do we know about RAM memory (properties)?

• It’s slow (compared to CPU)

• Random Access: Time to access data doesn’t depend on physical location of data on memory device.

What is memory stall?

BAD SITUATION; When CPU freezes and waits for data to be delivered in RAM.