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Computer science > Hardware (Paper 1) > Flashcards

Hardware (Paper 1) Flashcards

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1
Q

What does CPU stand for?

A

Central processing unit

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2
Q

What is the fetch, decode and execute cycle?

A

.Every instruction is fetched from the memory
.Once fetched it is decoded with the control unit to find out what to do next
.Then the instruction is executed

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3
Q

What does the arithmetic logic unit do (ALU)?

A

Carries out mathematical and logical operations including AND, OR and NOT binary shifts. it compares values held in registers

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4
Q

What does the control unit do (CU)?

A

Coordinates all of the CPU’s actions in a fetch, decode and execute cycle and decodes instructions. sends and receives control signals to fetch and write data

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5
Q

What does the clock do?

A

The clock regulates the speed and timing of all signals and computer functions

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6
Q

what do the registers do?

A

Very small, very fast memory locations. registers are built into the CPU chip to temporarily store memory addresses, instructions or data. they are used in the fetch decode and execute cycle for specific purposes

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7
Q

What do the address, data and control buses do?

A

Buses are wires used to transfer data, instructions, memory addresses of data and instructions, and control signals from one component to another

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8
Q

What does the current instruction register do (CIR)?

A

Holds the instruction that is currently being executed

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9
Q

What does the memory data register (MDR) do?

A

Holds data or a program instruction when it is fetched from memory or data that is waiting to be written to memory

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10
Q

What does the accumulator do (ACC)?

A

The accumulator is a register in which results of operations carried out in the ALU are stored

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11
Q

What is the program counter (PC)?

A

A register which holds the memory address of the next instruction to be processed

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12
Q

What is the function of the memory address register (MAR)?

A

Holds the address of the current instruction or piece of data to be stored or fetched

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13
Q

What does the clock speed determine?

A

The number of fetch, decode executes per second

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14
Q

What is the purpose of the CPU?

A

To continuously process instructions and data that are input by repeatedly carrying out the fetch, decode and execute cycle

The CPU contains the Arithmetic logic unit and the control unit in addition to several general purpose and special purpose registers

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15
Q

Define the term microprocessor

A

A type of integrated circuit on a single chip that processes instructions

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16
Q

Define the term core

A

Each processor may contain more than one core
Each core can process one operation per clock cycle
A dual or quad core processor will be able to perform 2 or 4 operations simultaneously

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17
Q

What is the role of cache memory in a CPU?

A

Since cache memory transfers quicker than main memory it makes the CPU more efficient which means less time is spent waiting for data to be transferred

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18
Q

What is an instruction set?

A

A list of specific commands written in machine code that can be understood and executed by the CPU

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19
Q

What is an embedded system?

A

Micro-processor based hardware system with software designed to carry out a specific function

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20
Q

What are some examples of embedded systems?

A

Vending machines, air conditioning units, microwaves, lighting systems and security systems

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21
Q

Why are embedded systems more reliable?

A

As they cannot be modified once manufactured and are carried out to perform one specific function

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22
Q

What is a scanner?

A

An input devices that all use reflected light to recognize a pattern or shape which a computer can convert into meaningful data

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23
Q

What is primary storage?

A

Main memory which is directly accessible to the CPU for example RAM and ROM

24
Q

What is the use of Random access memory (RAM)?

A

To temporarily store the instructions and data the computer needs whilst in operation

25
Q

What is the use of Read only memory (ROM)?

A

Stores instructions and data that never need to be changed such as the computer’s start up instructions

26
Q

What are the properties of RAM storage?

A

Volatile
Can be written to and read from
Used as the computer’s working memory for instructions, programs and data

27
Q

Define the term volatile

A

All data is lost when the power is turned off

28
Q

Define the term non-volatile

A

Data is permanently retained without power

29
Q

What are the features of ROM?

A

.Non-volatile
.Read only so it cannot be written to
.Used for the computer’s start up instructions and in embedded systems

30
Q

Define secondary storage

A

Storage that is not directly accessed by the CPU and is used for more permanent data storage

31
Q

What are some examples of secondary storage?

A

Hard drives (Internal and external)
USB flash drives
CDs

32
Q

Why is secondary storage needed?

A

As it is non volatile it is used for longer term storage of files and data

33
Q

What are the advantages of solid state drives (SSDs)?

A

They require little power and create little heat due to lack of moving parts
They are also small and reliable

34
Q

What are some examples of magnetic storage?

A

HDDs - Hard disk drives
Floppy disks
Magnetic tapes

35
Q

What are some examples of optical storage?

A

CD
Blu-ray

36
Q

What are some examples of solid state?

A

USB
SSDs

37
Q

What is virtual memory?

A

Virtual memory is used when there isn’t enough space in RAM for all the programs and data that you are currently working on

38
Q

How is virtual memory created and when is it necessary?

A

.For example if windows, word and a word document were open and loaded into the RAM from the hard disk
.This will fill up available space in the RAM completely
If you then try and open an excel file the .CPU must first move some spaces of data that compromise some files into virtual memory from the RAM
.This will free up enough space from the RAM entirely

39
Q

What are the advantages to cloud storage?

A

.Files are automatically backed up in the cloud
.Enables file sharing and collaboration
.One cloud storage centre is more environmentally friendly than millions of individual servers
.Remote file access with internet from anywhere

40
Q

What are the drawbacks to cloud storage?

A

.May need to commit to an annual subscription
.Backup and restore may be slower than local storage depending on your internet speed
.Requires internet access
.You may be responsible for any security breaches even though it may not be your fault
.Security of the data is managed outside the user’s control

41
Q

How does a barcode work?

A

-Red laser light is shone at the barcode to illuminate it
-The light from the white lines is reflected back again
-Black lines absorb the light so less is reflected
-Sensors within the scanner detect the pattern of strong and weak reflections from the lines
-The reflection strength from each line is interpreted by a microprocessor and converted unto a binary value

42
Q

How does a 2D scanner work?

A

-It shines a strip of light onto a document or photograph
-The strip moves over the whole document and as it does, the reflected light is captured using mirrors and lenses for each pixel
-This information is converted into a digital file to produce a digital image of the original document

43
Q

How does a 3D scanner work?

A

-Shines a light over the surface of an object
-It records the geometry and dimensions of the object to produce a digital file
-From this file a digital model of the original object can be created using specialist software
-Parts could then be printed using a 3D printer

44
Q

How does a QR scanner work?

A

-A QR code is read by using a camera commonly on a mobile device
-Three large squares are used for alignment
-The smaller black and white squares then reflect or absorb light in the same way as a barcode
-Software on the mobile device then converts each pixel into a binary value to process the image

45
Q

How does a keyboard work?

A

When a key is pressed on a standard keyboard a peg under the key is pressed into a springy layer to make contact with a conducting membrane

46
Q

How does an optical mouse work?

A

An optical mouse uses a red LED and a sensor to determine the movement of the mouse relative to a surface. The speed and distance of movement is then analysed by a digital signal processor to create the same movement of the mouse cursor

47
Q

How does a microphone work?

A

A microphone uses a diaphragm to vibrate in response to sound. The vibrations cause a coil to move around a magnet which creates changes in the electromagnetic field. Changes are detected and recorded by a processor using an analogue to digital converter (ADC)

48
Q

What are the different types of touch screens?

A

-Resistive
-Infra -red
-Capacitive

49
Q

How does a resistive touch screen work?

A

-They are made up of a layer of conductive polyester and a layer of conductive glass
-They are separated by an insulating membrane
-When the screen is gently pressed the two conducting layers make contact and complete a circuit
-The position where the screen is touched is calculated by a microprocessor

50
Q

Where are resistive touch screens commonly used?

A

-ATMs
-Medical equipment

(Where people often wear gloves)

51
Q

How do infra-red touch screens work?

A

LEDs shine infra-red light across the screen fro the top and sides
-The infra-red rays form a grid across the screen
-When the screen is touched by a finger the infra-red beam is interrupted and a microprocessor calculates the coordinates of where the screen was touched

52
Q

Where are infra-red touch screens commonly used?

A

Staff tills at fast food outlets

53
Q

How do capacitive touch screens work?

A

-Capacitive touch screens are made up of glass layers
-The bottom surface of the upper layer and top surface of the bottom layer are coated in perpendicular lines of transparent conductive material forming a grid
-The screen behaves like a capacitor storing electrical energy
-When the screen is touched by a finger there is a change in the electric field at that position
-The position where the field changes is calculated by a microprocessor
-They can be touched in more than one place at the same time unlike resistive screens

54
Q

How does a digital camera work?

A

-A digital camera contains a CMOS or CCD sensor
-As light enters the lens it falls onto the sensor which is divided up into millions of individual squares or pixels
-Each square measures the light intensity that falls on it and this value is converted into digital data as a pixel with a single binary colour value
-Using the information from each pixel the image can be stored as a file on a flash memory by a microprocessor

55
Q

How does an LCD (Liquid crystal display) screen work?

A

-They are made from millions of pixels

-Each pixel is a separate red, green and blue light which can be switched on or off electronically using liquid crystals

-To rotate polarised light

-The pixels are switched on or off very rapidly to create a moving colour picture

-A special fluorescent lamp is required for the necessary backlight

56
Q

How does an LED (light emitting diode) screen work?

A

-An LED screen uses the light from LEDs to produce a brighter backlight almost instantly

-This replaces the need for the additional fluorescent lamp required by LCD

57
Q

What are the advantages to an LED screen?

A

-They are thinner than LCD screens as they don’t need an additional backlight

-Therefore they would take up less space and be lighter to hang

-Their image is sharper than LCD which displays more realistic colours

-LED screens have a higher pixel density than LCD screens

-LEDs are very long lasting and consume very little power

Computer science (7 decks)

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