von neuwmann model

Question 1

6 Functions of a typical operating system

Answer 1

Muti-tasking, Error Handling, Security, Input and Output controls, Multi-Programming, Batch processing

Question 2

Define 4 of them

Answer 2

Muti-tasking: Allowing you to open may applications at a time.
Error Handling: Refers to the anticipation, detection and resolution of programming, application and communication errors.
Security: Passwords, no information will be leaked.
Input and Output controls: Controlling other devices like printers.

Question 3

What is an interrupt?

Answer 3

An interrupt is a signal that is sent from a device or a software to the processor that would cause the processor to temporarily stop what it is doing and service the interrupt.

Question 4

Reasons for an interrupt to occur

Answer 4

• disk drive ready to receive more data
• error has occurred
• <del> buttons pressed simultaneously</del>
• software error has occurred</del>

Question 5

2 Types of interrupt

Answer 5

Hardware interrupt: signals sent from external devices or hardware
Software Interrupt: signals such as when applications are closed or open on the system

Question 6

What is a Buffer?

Answer 6

temporary memory area that is used to compensate speed difference between 2 communicating devices.

Question 7

2 Types of buffers

Answer 7

Print buffers: for example, stores number of jobs sent to the printer by the people. Lists them in order in the buffer memory showing whether it is waiting for their turn or is being printed.
DVD Buffers: when adding data into the DVD, applications loads the data into the burner buffer that would be stored in the DVD. The burner software loads it into the empty DVD. it makes sure that the burner doesn’t run out of data therefore speeding and slowing down controlling rate of data coming in and out.

Question 8

Describe the structure of the Von Neumann Model.

Answer 8

INPUT DEVICE= CPU { Control unit and Arithmetic/Logic unit} -_-Memory unit = OUTPUT DEVICE

Question 9

List the main components of the model.

Answer 9

Control unit
Memory Unit
Processing unit

Question 10

Define the main components of the model.

Answer 10

Controls the flow of data and tells different components how to respond with instructions given.
(includes Program counter instructions from components in computer.
Current Instruction Register holding all data to be sent to the processing unit to be outputted on the screen.

CPU needs to hold data and instructions before processing therefore is stored in the memory unit.
Data loaded into main memory and brought to Immediate access store.
(MAR and MDR)

ALU used to carry calculations on data. Values placed in the accumulator for calculations to be carried out.
Also includes temporary register.

Question 11

What is a bus?

Answer 11

group of wires that carries signals including data, memory address and instructions between components of a computer system.

Question 12

List the 3 different types of buses

Answer 12

Address bus
Data bus
Control bus

Question 13

define them.

Answer 13

AB:
one way traffic.between processor and memory. carries signals relating to memory addresses.
DB:
two way traffic. between processor, memory unit and input/output devices.
exchange data.
CB:
one way/two way traffic. between processor- other devices or interrupts from other devices- processor.
control and coordination.

Question 14

Define register and accumulator.

Answer 14

register: high speed storage areas in the CPU. holds data and instructions during processing.
accumulator: register used for calculations.

Question 15

Different types of registers.

Answer 15

MAR
MDR
AC
PC
CIR

Question 16

define them.

Answer 16

-Memory address register:
Holds memory location of data to be accessed
-Memory Data Register:
Holds data that is being transferred to or from the memory.
-Accumulator:
Where intermediate arithmetic and logic results are stored.
-Program Counter:
Contains address of the next instruction to be executed.
-Current Instruction Register:
contains the instructions currently being used during processing.

Question 17

Describe the read operation

Answer 17

Value taken from computer memory to display on screen. Address of location first read is written to MAR. read signal sent to memory using control bus. contents then put into MDR. stored as binary data. goes to ALU and is executed.

Question 18

Describe write operation

Answer 18

information saved on hard drive. operation opposite to read operation.

Question 19

What is fetch execute cycle

Answer 19

Fetch execute cycle is the basic operation cycle of a computer. Computer receives instructions from its memory. Establishes, carries out actions required for the instructions. Cycle continuously repeated by the CPU while computer is turned on.

Question 20

What are the steps in the fetch execute cycle

Answer 20

1. PC stores the address of the next instruction
2. PC contents copied onto the MAR
3. MAR contents copied onto the MDR
4. MDR contents copied onto the CIR
5. PC is incremented by 1
6. Instruction is decoded and executed
   repeat