4.7.1 Internal Hardware components of a compute 4.7.2 The stored Program concept

Question 1

Explain the role of the processor?

Answer 1

1) The Processor responds to and processes the instructions that drive the computer
2) It contains the control unit, the arithmetic logic unit (ALU) and the registers
3) The control unit coordinates and controls all the operations carried out by the computer

4) The processor repeats the following operations
- Fetch: Causes nest instruction to be fetched from memory
- Decode: Decodes the instruction
- Execute: Causes the instructions o be executed

Question 2

What is the function of the ALU?

Answer 2

The Arithmetic Logic Unit (ALU) performs:

1) Addition
2) Subtraction
3) Multiplication
4) Division

Question 3

What is a bus? (ADC)

Answer 3

A bus is a set of parallel wires connecting two or more components of a computer the processor connects to the main memory via three main busses

1) Address Bus
2) Data Bus
3) Control Bus

Question 4

What is the address bus?

Answer 4

1) The address bus is used to transport memory location addresses of the register the data is being carried to
2) The width of the address bus determines the maximum possible capacity of the system

Question 5

What is the data bus?

Answer 5

1) The data bus is bi-directional for carrying data and instructions between the processor and memory
2) Width of the data bus is important towards the overall performance
3) If the bus is 8 bits wide and each instruction is 16 bits wide the processor must access the main memory twice to fetch the instruction

Question 6

What is the control bus?

Answer 6

1) Bi-Directional bus that carries signals

2) Transmits command timing and specific status information between the system components

Question 7

What are the I/O controllers?

Answer 7

1) An I/O controller is a device that interacts between an input or output device and the processor
2) The device has a separate controller that connects to the control bus
3) Controllers receive input and output from the processor and then send back specific control signals to the device that they control

Question 8

What is main memory?

Answer 8

1) Main memory is memory that can be accessed directly by the processor. The main memory consists of memory locations that store instructions or data. There are two types of main memory:
1) volatile memory, which loses its contents when the power is removed
2) non-volatile memory, which keeps its contents even without power

Usually refers to RAM (random access memory) which is a volatile memory

Question 9

What is the Von Neumann architecture?

Answer 9

1) This architecture specifies the basic components of the computer and processor in which a shared memory bus is used for both data and instructions
2) Makes use of the stored program concept where machine code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations
3) This architecture is used extensively in general-purpose computing systems

Question 10

What is the Harvard architecture?

Answer 10

1) A computer architecture with physically seperate memories for instructions and data
2) Used in embedded systems such as Digital processing systems (DSP)

Question 11

What is the difference between the Von Neumann and Harvard architectures?

Answer 11

1) Harvard architecture is faster than Von Neuman as data and instructions are fetched in parallel rather than competing for the same bus

Question 12

What is the function of the control unit?

Answer 12

1) The Control unit controls and coordinates the activities of the CPU directing the flow of data between the CPU and other devices
2) It accepts instructions, breaks them down into sequential steps, manages execution and stores the result in memory and registers

Question 13

What is the System clock?

Answer 13

1) Generates a series of signals between 0 and 1 billion times a second
2) Synchronizes CPU Operations
3) E.g. A 3GHz processor’s clock ticks three billion times per second
4) Operations start as the clock changes from 0 to 1 and the CPU cannot perform operations faster than the clock cycle

Question 14

What are General Purpose registers (Accumulator) ?

Answer 14

1) 16 registers in a CPU
2) All arithmetic, logical and shift operations occur in registers

3)

• Load contents of 150 into R1
• Add contents of 164 to R1
• Store contents of R1 to 170

4) Also known as a accumulator

Question 15

What is the program counter (PC)?

Answer 15

1) Hold the address of the next instruction to be executed

2) E.g. Next instruction in a sequence of instructions

Question 16

What is the Current instruction register (CIR)?

Answer 16

1) Holds the current instruction being executed

Question 17

What is the memory address register?

Answer 17

1) Holds the address of the memory location from which data (or an instruction) is to be fetched or to which data is to be written

Question 18

What is a memory buffer register? (MBR)

Answer 18

1) Used to temporarily store the data read from or written to memory

Question 19

What is a Status register?

Answer 19

1) Contains bits which are set or cleared depending on the result of an instruction

2) E.g. One bit could be set if an overflow occurs
Other bits may indicate whether a result of the last instruction was negative, zero or caused a carry

Question 20

What is the Fetch-code-Execute cycle?

Answer 20

1) Sequence of operation involved in executing an instruction

2) Divided into 3 sections:
- Fetching
- Decoding
- Executing

3) This cycle is repeated over and over as each instruction of the program is executed

Question 21

Explain the Fetch phase of the cycle including the registers used? (Step 1)

Answer 21

1) Address of next instruction copied from Program Counter (PC) to the memory address (MAR)
2) Address is sent via the address bus to the main memory
3) The instruction in that address is returned to the memory buffer register
4) At the same time the content of the PC (Program Counter) is incremented to hold the address of the next instruction
5) The content of the MBR is copied onto the CIR (Current Instruction Register)

Question 22

Explain the Decode Phase of the cycle including the registers used? (Step 2)

Answer 22

1) Instructions inside of the CIR is decoded and split into opcode and operand
2) Opcode used to determine the type of instruction and what hardware is used to execute it

Question 23

Explain the Execute Phase of the cycle including the registers used? (Step 3)

Answer 23

1) Instructions are executed using the ALU if required

2) The results are stored in the accumulator, general purpose register or memory

Question 24

What is meant by processor instruction set?

Answer 24

1) Processor instruction set is processor specific and it is a set of all the instructions that are supported by its hardware

Question 25

Understand a Barcode Reader?

Answer 25

1) Two different types of barcode linear barcode and 2D barcode
2) 2D barcodes store more information in the same space as a 1D barcode but they require more processing
3) The pattern of light and dark strips in a barcode represents binary 1’s and 0’s
4) Barcodes have error detection such as parity bits and check digits which check if a barcode has been read correctly

Question 26

Understand a digital camera?

Answer 26

1) A digital camera consists of a lens that focuses light onto a sensor the path of light is regulated by a shutter
2) Two common sensors used are CMOS and CCD which convert incident light into electrical charge

Question 27

Understand a Laser Printer?

Answer 27

1) A laser printer is an output device that produces images on paper from digital signals
2) Drum +ly charged toner is -ly charged opposites attract
3) Paper is heated by fusers and the toner is fixed to the paper

Question 28

Understand RFID Radio Frequency Identification?

Answer 28

1) Method of transferring information wirelessly
between a tag and a reader

2) Contains a chip with a small amount of memory and a coil is attached to it which acts as an antenna

3) When an RFID tag is scanned, the reader emits radio waves which are picked up by the
tag’s antenna

Question 29

What is a Hard Disk?

Answer 29

1) A Hard disk consists of a number of circular platters which are made from a magnetic material. Above each platter hovers an actuating arm on which is a read/write head.