CPU,Memory And Program Execution

Question 1

What does the “memory” part do?

Answer 1

It stores both the program while it is running and the data on which the program operates.

Question 2

What properties does the “memory” have and explain its functions?

Answer 2

1. Discrete locations - It is is organised as a sequence of discrete locations
2. Address - Every memory location has an address, whole numbers starting at 0
3. Values - Memory locations record/store values
4. Finite capacity- This means that the memory locations have a finite capacity.

Question 3

Define Random Access Memory (RAM)

Answer 3

This is the name for computer memory

RAM is measured in megabytes (MB),gigabytes (GB) or terabytes (TB)

Lots of memory is needed to handle the space required of programs and data

Question 4

What does the control unit do?

Answer 4

The control unit of a computer is where the Fetch/Execute cycle occurs.
- It fetches an instruction from memory and performs the other operations of the Fetch/Execute Cycle on it.

Question 5

What is a typical instruction formation in a computer system?

Answer 5

The typical machine instruction is : ADD 4000,2000,2080

Question 6

What does it really mean from the instruction formation?

Answer 6

So what ever the numbers are stored in memory locations 2000 and 2080 be added together and the result be stored in locations 4000.

Question 7

What does the arithmetic Logic Unit (ALU) do?

Answer 7

It does the maths

The circuit in the ALU can add/subtract two numbers

The circuit uses logic gates or simpler circuits that implement operations like AND and OR

There’s another circuits for multiplying, for comparing two numbers etc.

ALU carries out each machines instruction with a separate circuit

Question 8

What does the Input/output units do?

Answer 8

The two components are the wires and circuits through which information moves into and out of a computer.

A computer without input or output is useless

Question 9

What does the peripherals do?

Answer 9

It connect to the computer input/output (I/O) ports

They provide input or receiving its output

Question 10

What does the peripherals do?

Answer 10

It connect to the computer input/output (I/O) ports

They provide input or receiving its output

Question 11

Why isn’t “Peripherals” not considered as part of the computer?

Answer 11

It because they only specialised gadgets that encode or dead code information between the computer and the physical world.

E.g keyboard, mouse, USB, Network cards

Question 12

How do we execute programs?

Answer 12

The program is loaded into memory and address of FIRST INSTRUCTION is placed in PC (Program Counter)

Question 13

What are the steps of the Fetch/ Execute cycle after the first instruction?

Answer 13

1. Instruction Fetch (IF)
2. Instruction decode (ID)
3. Data/ Operand Fetch (DF/OF)
4. Instruction Excution (EX)
5. Result return/ store (RR/ST)

Question 14

What does the instruction Fetch (IF) function?

Answer 14

Move instruction from memory to the control unit

Question 15

What does the Instruction Decode (ID) determines?

Answer 15

It determines what operation the ALU will perform (ADD) and sets up the ALU

Question 16

What are the two things decoder finds in the computer system?

Answer 16

1. It finds the memory address of the instruction’s data (source Operands)
2. It finds the destination address for Result Return step and places the address in the RR circuit.

Question 17

What is the instruction decode function?

Answer 17

It pull apart the instruction,set up the operation in the ALU, and computer the source and destination operand addresses.

Question 18

What is the function of ‘Data Fetch’ (DF)?

Answer 18

It moves the operands from memory to the ALU

Answer 19

Data values to be operated on are retrieved from memory.

Data values remain in memory ( they are not destroyed)

Question 20

What is the function for Instruction execute?

Answer 20

Computer the result of the operation in the ALU

Question 21

What is the function of the Result Return?

Answer 21

Store the result from the ALU into the memory at the destination address.

Answer 22

RR returns the result of EX to the memory location specified by the destination address

Once the result is stored the cycle begins again.