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Flashcards in Low Level Operations And Structure Deck (28):
1

What is the purpose of the ALU during program execution?

To carry out calculations and make any logical decisions such as comparing two values

2

What is the purpose of the registers during program execution?

The registers are used if the instruction requires that data be temporarily stored during processing.
Some are for general use whilst others have a specific role such as the program counter which stores the address of the next instruction to be fetched.

3

What is the purpose of the control unit during program execution?

Responsible for overseeing all operations within the processor. These include;
Timing each event using the computer systems clock.
Initiating the transfer of data along the data bus by activating the read and write lines of the control bus
Interrupting the processor if another task (process) needs dealing with
Telling the ALU how to respond to various instructions.

4

What steps are involved in the memory read operation?

1. The memory address of the data to be fetched is placed in the memory address register (MAR)
2. The read line on the control bus is activated by the control unit
3. The data is located at the memory address specified by the address bus and is sent along the data bus to the memory data register.

5

What steps are involved in the memory write operation?

1. The memory address of the data to be fetched is placed in the memory address register
2. The data to be written is placed in the memory data register (MDR)
3. The write line on the control bus is activated by the control unit
4. The data is sent along the data bus and stored in the memory address specified by the address bus.

6

How has CPU technology developed since Von Neumanns original design?

1. Buses have widened - allowing for more memory addresses and more data stored on these addresses
2. Multi core processors allow more than one instruction to be processed at one time. This allows them to effectively run more than one program at one time e.g running a JavaScript program in a web page whilst playing an embedded video
3. Faster types of memory are used to predict and store instructions to be executed through wider buses and being located closer to or within the processor.

7

What are some of the differences in functionality between peripheral devices and the CPU?

Peripherals -
Use Different voltages
Transfer data differently
Use serial transmission
Can be analogue devices
Transfer data at different speeds

8

How does an interface compensate for the differences between the CPU and peripheral devices?

Converting an analogue to a digital signal and vice-versa
Converting serial transmission (one bit being sent down a single wire) to parallel data (multiple bits being sent down multiple wires simultaneously) for transfer down an internal bus
Temporarily storing data in a buffer until a slower peripheral device is ready to receive it
Using status signals to ask the current state of an external device

9

What is an emulator?

An emulator is a program that imitates the behaviour of another computer system - usually used to test circuits and computer systems before they are built or to simulate old systems such as games consoles

10

What is meant by a mobile device?

A notebook, smartphone or tablet

11

What is a virtual machine?

A type of emulator that recreates a complete substitute of a full computer system.
These may be cloud based and purchased on a subscription basis.

12

What is the function of each CPU bus?

Data Bus - To carry data to and from the registers and into memory it is bidirectional.
Address Bus - Used to specify memory locations where instructions/data are stored. Unidirectional.
Control Bus - Used by the CPU to communicate with devices within the computer. Bidirectional.

13

What steps are involved in the fetch execute cycle during program execution?

1. The memory address of the next instruction to be fetched is placed in the memory address register (MAR)
2. The read line of the control bus is activated by the control unit
3. The instruction is located at the memory address specified by the address bus and is net along the data bus to the memory data register
3. The instruction is transferred to the instruction register, where it is decoded and executed

14

What is Unicode?

A character encoding standard used for the representation of 65536 characters
This means that it can represent a wide range of character sets

15

Bit Depth

The number of bits used to store each pixel in an image

16

How are vector graphics stored?

Stored as a list of attributes
Scalable, support layering and are resolution independent

17

Why does cache memory provide faster access than main memory?

It uses static RAM as opposed to dynamic RAM

18

What is parallel to serial conversion?

A data format conversion where data is sent down one line in sequence (Serial) to multiple lines simultaneously (Parallel)

19

Emulator

Designed to allow software on a system to behave in a way that hardware and software on a different system would behave
Eg Dated Gaming Devices

20

What does the exponent represent?

The exponent dictates the range of numbers which can be represented when using floating point notation

21

What is word size?

The amount of bits that can be transferred via the data bus in one fetch/execute operation

22

What is the control unit on the processor responsible for?

Provides timing and regulator signals to allow the CPU to carry out the fetch/execute cycle

Eg Read, Write, Interrupt

23

What is the purpose of a wireframe?

A graphical representation of a potential user interface layout

24

Data Dictionary Purpose

Hold data that defines the characteristics of each entity

25

What are wire frames commonly used for?

Design of an interface layout
Used when there are a range of mobile devices
This includes text holders, image holders and video placement

26

What is an entity?

A person, place or object about which data can be stored

27

How are many-to-many relationships resolved when designing an entity relationship diagram?

By creating an associate entity that link to both entities with one to many cardinality

28

Why do many people prefer the use of a structure diagram to pseudocode?

Some programmers prefer a visual design to a more formal written structure