1.2 - The Fetch Execute Cycle

Question 1

Where is the computer’s memory?

Answer 1

The computer’s memory is very close to the CPU.

Question 2

How is the CPU and Memory joined?

Answer 2

By buses

Question 3

When people refer to the CPU and Memory , what do they call it?

Answer 3

Processor

Question 4

What are three memory types?

Answer 4

Secondary storage: is used to save user data files and program files in a non-electrical form until they are needed by the processor.

Immediate Access Store (IAS): Computer’s ability to go directly to a requested file or piece of data instead of sifting through a list

Random Access Memory (RAM): primary storage that holds data ready to be used by the CPU.

Question 5

What does memory hold?

Answer 5

-The instructions that tell the computer what to do.
-The data values that the computer needs
-The results of the CPU’s work.

Question 6

How do modern computers transfer data and instructions differently?

Answer 6

In a modern computer the instructions and data are held in the same memory. But they go down two different buses to the CPU.

Question 7

When the CPU completes an instruction, what does it do with the results?

Answer 7

It sends the results back to memory

Question 8

What is memory made up of ?

Answer 8

-Memory is made of microscopic electrical circuits.

Question 9

How does memory work?

Answer 9

The memory circuits can be on or off. Everything inside the memory is stored using these on / off signals.

Question 10

How is data stored in memory?

Question 11

How is data lost in memory ?

Answer 11

Data is stored in memory as electrical signals. But if the electricity is turned off, all the data will be lost.

Question 12

What happens when you save your work?

Answer 12

Data is copied from memory to storage

Question 13

What are some examples of storage ?

Answer 13

-The hard disk of your computer
-A flash memory drive
-The storage on your school network
-Cloud storage on the internet

Question 14

What is another name of storage ?

Answer 14

Secondary storage

Question 15

What is secondary storage?

Answer 15

Peripherals such as storage drives. Secondary storage is used to save user data files and program files in a non-electrical form until they are needed by the processor.

Question 16

What are the advantages of RAM (electronic memory)?

Answer 16

RAM is very close to the CPU. The CPU can get data and instructions form RAM easily and quickly.

Question 17

What are the disadvantages of RAM (electronic memory)?

Answer 17

The disadvantage of RAM is that it’s contents are lost when the computer is switched off.

Question 18

What are the advantages of the secondary storage ?

Answer 18

The secondary storage can keep data and instructions safe when they are not needed, or when the computer is turned off.

Question 19

What are the disadvantages of secondary storage?

Answer 19

Secondary storage is further away from the CPU. It takes longer for the CPU to get data and instructions from the secondary storage than from RAM.

Question 20

What is the fetch-execute cycle?

Answer 20

The actions that take place in a CPU during a single processing cycle.

Question 21

What are the fetch-execute cycle steps?

Answer 21

1) Fetch
2)Decode
3)Execute
4)Save

Question 22

Describe the Fetch step:

Answer 22

The control unit ‘fetches’ the instruction from RAM. The instruction travels down the bus from RAM to the control unit.

Question 23

Describe the Decode step:

Answer 23

The instruction is in the form of a binary code. The control unit knows all the binary number codes. The control unit ‘decodes’ the instruction, so it knows what to do.

Question 24

Describe the Execute step:

Answer 24

The control unit sends a signal to the ALU to tell it what to do. The ALU carries out the instruction. ‘Execute’ means carry out an instruction.

Question 25

Describe the Save step:

Answer 25

If the instruction produces a result, then the ALU sends the result back to RAM.

Question 26

In what form does the instruction arrive to the control unit?

Answer 26

In binary numbers

Question 27

Which part of the CPU know binary codes?

Answer 27

Control unit

Question 28

What 2 things affect the speed of the computer?

Answer 28

-The speed of the clock -The size of the memory

Question 29

What happens if a computer has lots of RAM?

Answer 29

If a computer has lots of RAM, then all the data and instructions can fit into the memory. The CPU can get the data and instructions very quickly . The computer will go quickly.

Question 30

What happens if a computer doesn’t have very much memory?

Answer 30

If a computer doesn’t have very much memory, then the data and instructions won’t all fit into the memory. Some will have to wait in storage . The CPU will get the data and instructions slowly. The computer will go more slowly.

Question 31

What is cache ?

Answer 31

A small area of primary storage that holds data and instructions that are about to be processed by the CPU.

Question 32

How close is the cache to the CPU?

Answer 32

The CPU has a small amount of memory (cache) which is even closer than RAM.

Question 33

What happens if a computer has a big cache?

Answer 33

It is very quick for the CPU to get data and instructions from cache. If a computer has a big cache then it will be able to get all the dat and instructions quickly.

Question 34

What is word size?

Answer 34

The amount of data that a computer can fetch and use in one cycle is called the ‘word size’.

Question 35

How is the size of the buses in different word sizes?

Answer 35

Computers with a larger word size tend to have larger buses so they can carry more data in one cycle.

Question 36

How does word size affect a computer’s speed?

Answer 36

A computer with a larger word size generally works more quickly