Section 1 - Computer Science - Components of a Computer System

What are the two main types of computer systems?

• General-purpose systems (like PCs)

• embedded systems (built into devices like washing machines or microwaves or watches).

What is the main function of the CPU?

To fetch, decode, and execute instructions (the FDE cycle).

Name the three main parts of the CPU

Control Unit (CU), Arithmetic Logic Unit (ALU), and Registers.

What does the Control Unit do?

It manages the FDE cycle and controls the flow of data inside the CPU.

What is the role of the ALU?

Performs Arithmetic calculations and logic operations

What are registers used for in the CPU

Temporarily hold small amounts of data and instructions.

What are two types of memory in a computer?

RAM ( Random access memory )

ROM ( Read only memory )

How does RAM affect performance? Is RAM volatile or non volatile?

More RAM allows more programs to run smoothly at once. RAM is volatile.

What is secondary storage used for? Are they volatile or non-volatile?

To store data and programs when the computer is turned off. They are non-volatile

Give examples of secondary storage devices

Hard drives, SSD’s, CD’s and USB drives

What are the two types of system software?

Operating systems

Utility software

What does an operating system do?

Manages hardware, software, users, and files.

What is utility software?

Software that helps maintain or configure a computer, e.g., antivirus, backup tools.

What factors affect CPU performance?

Clock speed, number of cores, and cache size.

What is the difference between volatile and non-volatile memory?

Volatile memory (like RAM) loses data when power is off; non-volatile (like ROM or SSD) keeps it.

What is the function of RAM and ROM?

RAM temporarily stores data and programs that are currently in use by the CPU. It is volatile, meaning it loses data when the power is off.

ROM permanently stores essential instructions for booting the computer, like the BIOS. It is non-volatile, so it keeps data even when the power is off.

Is ROM volatile or non-volatile?

Non-volatile

What is the cache and what does it do?

Cache is a small amount of high-speed memory located inside or very close to the CPU. It stores frequently used data and instructions so the CPU can access them quickly, improving processing speed.

What is clock speed and what does it do?

Clock speed is the number of cycles the CPU can carry out per second, measured in Hertz (Hz). A higher clock speed means the CPU can process instructions faster, improving performance.

What are the 2 registers in Von Neumanns model of the CPU?

MAR ( memory address register )

MDR ( memory data register )

What does the memory ( MAR and MDR ) do?

Holds the program instructions and the program data

What is the first instruction of the Fetch-execute cycle? What happens?

Step 1 - Fetch instruction - The CPU copies memory address from the PC in the CU. CPU copies the instruction stored in the MAR to the MDR. CPU increases the PC to point to the address of the next instruction.

What is the second instruction of the fetch - execute cycle? What happens?

Step 2 - Decode instruction - The instruction in the MDR is decoded by the CU. The CU may then prepare for the next steps for example by loading values into the MAR or MDR.

What is the third instruction of the fetch- execute cycle? What happens?

Step 3 - Execute instruction - The instruction is executed. E.g. Load data from memory, write data to memory, do a calculation using the ALU.