4 - Computer Systems

Question 1

What is a computer system?

Answer 1

A computer system takes a set of digital inputs, processes them and creates a set of outputs. This is done by a combination of hardware and software.

Question 2

Hardware

Answer 2

Hardware is the physical components that make up a computer e.g. keyboard

Question 3

Software

Answer 3

Software is human-written programs that contain instructions on how the hardware will operate

Question 4

Role of the CPU

Answer 4

CPU processes data. It does this by fetching instructions from memory (RAM), decoding the instructions and then executing them

Question 5

What does the CPU do as well as processing data?

Answer 5

The CPU controls all of the component parts of a computer e.g. the hard disk

Question 6

Where is the CPU located?

Answer 6

In the motherboard

Question 7

What are the 3 main parts of the CPU?

Answer 7

Control Unit
Arithmetic Logic Unit (ALU)
Registers

Question 8

What is the role of the ALU?

Answer 8

To handle all of the data processing inside the CPU. The arithmetic part deals with arithmetic operations. The logic part deals with logic and comparisons.

Question 9

What is the CPU clock?

Answer 9

A tiny quartz crystal inside the CPU chip that ticks at a steady speed. During each tick the CPU processes and executes a single instruction.

Question 10

What are CPU clocks measured in/

Answer 10

They are measured in Hz. 1 GHz enables 1 billion instruction to process every second

Question 11

What is Von Neumann architecture?

Answer 11

Von Neumann is where both the data and the software currently being used are stored in the RAM.

Question 12

What does the Control Unit do?

Answer 12

It handles the movement of data and instructions around the computer.

Question 13

What are buses and what do they do?

Answer 13

The buses are collections of wires through which data is transmitted from one component to another in a CPU

Question 14

What is main memory (RAM)?

Answer 14

RAM is where the programs and data whilst in use are stored

Question 15

What are registers?

Answer 15

Registers are a very small but fast type of memory which can hold a data value in use by the CPU

Question 16

What is the fetch-decode-execute cycle?

Answer 16

The fetch-decode-execute cycle is where the CPU continuously reads instructions stored in main memory and executes them as required

Question 17

How is the first instruction fetched?

Answer 17

The first instruction in the program is loaded (fetched) from main memory into the CPU.

Question 18

How is the next instruction fetched?

Answer 18

The next instruction’s location of the RAM is loaded into the program counter, and then is copied to the MAR. After this, the control unit copies the instruction from the MAR onto the address bus. The RAM then reads the contents of the location and loads it onto the data bus. The content is then loaded onto the Data bus and is copied to the MBR. After this, the instruction from the MBR is copied to the instruction register.

Question 19

What registers are involved in the Fetch-Decode-Execute cycle?

Answer 19

Memory Buffer Register (MBR)
Program Counter
Accumulator
Instruction register
Memory Address Register (MAR)

Question 20

How is the instruction decoded?

Answer 20

The control unit reads the contents of the MBR, and checks that it is a valid instruction. The CPU determines exactly which operation is to be executed.

Question 21

How is the instruction executed?

Answer 21

The control unit sends signals to the ALU, which may perform a logic comparison or calculation.

Question 22

How is the fetch-decode-execute cycle a cycle?

Answer 22

Once each instruction is executed, the control unit increments the program counter and uses it to find the next instruction to be fetched, and the cycle begins all over again.

Question 23

What is the effect of clock. speed on the CPU?

Answer 23

The faster the clock, the more instructions the processor can complete per second. However, if this is too high it can cause the CPU to overheat.

Question 24

What is a core?

Answer 24

A core is a complete processing unit within the CPU, which has an ALU, a control unit and registers.

Question 25

What is the effect of the number of cores on CPU performance?

Answer 25

CPUs with multiple cores have more power and can therefore run a number of programs at the same time

Question 26

What is cache?

Answer 26

Cache is a special type of memory which is volatile, and can be accessed much faster than RAM

Question 27

What is the effect of cache size on CPU performance?

Answer 27

The larger the cache size, the better the performance because the computer is able to store more data

Question 28

What is the effect of cache type on CPU performance?

Answer 28

Level 1 cache is extremely fast but relatively small
Level 2 cache is larger than level 1 but slower
Level 3 cache is a specialised memory that works to improve levels 1 and 2.
As cache speed increases, less memory is available

Question 29

What are embedded systems?

Answer 29

A system that has computer hardware with software embedded in one of its components

Question 30

What are some examples of embedded systems?

Answer 30

treadmill, ATM, car system, microwave oven, mobile phone, TV remotes, washing machines

Question 31

How does an embedded system differ from a non-embedded system? (2 differences)

Answer 31

an embedded system doesn’t load and execute other applications, which means the system is only able to run a single application, whereas non-embedded systems do

the software of an embedded system is custom-written, to work with its specific hardware. Non-Embedded systems are more general purpose

Question 32

Non-embedded systems examples

Answer 32

Laptops, Desktops, Tablets

Question 33

What is the purpose of an operating system?

Answer 33

An operating system primary purpose is to allow applications software to communicate with the hardware.

Question 34

Where may the result of a fetch-execute cycle be stored?

Answer 34

The results of this may be stored in a register in the CPU, or may be returned to main memory if the program requires it.