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GCSE OCR COMPUTER SCIENCE P1 > 1.1/1.2 > Flashcards

1.1/1.2 Flashcards

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1
Q

what is a computer?

A

an electronic device which takes input, processes data and delivers output

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2
Q

what is the purpose of the cpu?

A

To fetch, decode and execute instructions

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3
Q

what happens at the ‘fetch’ stage in the fetch-execute cycle?

A

fetches the next instruction from the main memory (RAM). Brings the instruction back into the cpu.

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4
Q

what happens at the ‘decode’ stage in the fetch-execute cycle?

A

inspects the instruction and works out what it is that needs doing.

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5
Q

what happens at the ‘execute’ stage in the fetch-execute cycle?

A

carries out the instruction (e.g going back to main memory and grabbing some data,performing a calculation , storing info back into main memory)

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6
Q

what are the common cpu components

A

arithmetic logic unit (ALU) , control unit (CU) , cache , registers

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7
Q

what is the purpose of the ALU?

A

performs calculations and logical decisions

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8
Q

what is the purpose of the CU?

A

sends signals to control how data moves around the CPU

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9
Q

what is the purpose of the cache?

A

provides fast access to frequently used instructions and data

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10
Q

what is the purpose of registers?

A

tiny,super fast pieces of onboard memory inside the CPU each with a very specific purpose

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11
Q

what does the Von Neuman architecture consists of?

A

control unit (cu) , arithmetic logic unit (alu) , memory unit (typically ram) , inputs and outputs.

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12
Q

what are the names of registers in the Von Neuman architecture?

A

program counter (pc) , memory address register (mar) , memory data register (mdr) , accumulator

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13
Q

what is the purpose of the program counter?(register)

A

holds the address of the next instruction in memory

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14
Q

what is the purpose of the memory address register?(register)

A

holds the address of where data is to be fetched or stored

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15
Q

what is the purpose of the memory data register?(register)

A

holds the data fetched from or to be written to memory

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16
Q

what is the purpose of the accumulator?

A

holds the result of calculations

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17
Q

what factors affect cpu’s performance?

A

Clock speed, Cache size, Number of cores

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18
Q

how does ‘clock speed’ affect the cpu’s performance?

A

the more pulses per second the more fetch-decode-execute cycles.

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19
Q

how does ‘cache size’ affect the cpu’s performance?

A

the bigger the cache the less time a processor has to wait for instructions to be fetched.

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20
Q

how does the ‘number of cores’ affect the cpu’s performance?

A

(each core is capable of fetching, decoding and executing its own instruction) More cores a cpu has the greater the number of instructions it can process in a given space of time.

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21
Q

what is a cpu called with 2 cores?

A

dual core

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22
Q

what is a cpu called with 4 cores?

A

quad core

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23
Q

how could dual core affect performance?

A

a program is split into two or more parts and each part is processed at the same time) In theory this would double performance on a dual core cpu as each part is processed independently. ​(however, you do not always get twice the performance because many programs cannot be split neatly into two independent parts​).

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24
Q

What is an embedded system?

A

a computer system that is built into another device

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25
what are the characteristics of an embedded system?
low power consumption , small size , rugged operating ranges , low cost per unit .
26
what are examples of an embedded system?
traffic lights, factory equipment hospital equipment
27
why do computers need primary storage?
holds the data and instructions which the CPU needs access to while a computer is running , the CPU = quickly access data fronts primary storage
28
what does the primary storage consist of?
random access memory (RAM) , read-only memory (ROM) , registers and cache
29
what is the purpose of RAM?
holds the operating system, programs and data in use by the CPU when the computer is running.
30
what is the purpose of ROM?
holds the first instruction for when the computer is first turned on (known as bootstrap)
31
what are the characteristics of RAM?
volatile (contents lost when the power is turned off) read and write large
32
what are the characteristics of ROM?
non-volatile (contents remain when power is turned off) read only small in comparison to RAM
33
why might virtual memory be needed in a system?
virtual memory is needed when there is not physical RAM to store the open programs (virtual memory is held on the hard disk)
34
how does virtual memory work?
programs are transferred out to virtual memory from the RAM when they are not currently being executed . programs are transferred back to RAM from virtual memory when they are needed.
35
why do computers need secondary storage?
to keep programs and data indefinitely.
36
what is secondary storage needed for?
-Storage of programs and data when the power is turned off. -Semi-permanent storage of data that can change -Backup of data files -Archive data files
37
what are the common types of storage?
optical (CD-R/RW , DVD-R/RW , Blu-ray) Magnetic ( Hard disk drive , tape) Solid - state (SSD , Memory sticks , Flash memory , memory cards)
38
what are the features of optical storage?
low capacity , compared to other types of storage slow to access data thin , lightweight and portable
39
what are the features of magnetic storage?
high storage capacity quick to access data has moving parts which eventually fail hard disks perform better if they are defragmented
40
what are the features of solid state storage?
medium storage capacity very quick to access data no moving parts , very reliable no noise low power no need to de-fragment limited number of read/write cycles expensive compared to others
41
what is optical storage suitable for?
Read only data distribution on a large scale and small capacity situations
42
what is magnetic storage suitable for?
when high data capacity is required , fast access to data , low cost situations and cloud storage on server forms
43
what is solid state storage suitable for?
low power , small embedded system rugged applications :portable devices small to medium data capacity requirements silent operation very fast access to data situations where the devices need to be small and lightweight
44
what are the advantages/disadvantages of optical storage?
advantages - cheap , lightweight , portable disadvantages - slow access times , prone to scratches
45
what are the advantages /disadvantages of magnetic storage?
advantages - cheap , large capacity disadvantages - slow access times , fragile
46
what are the advantages/disadvantages of solid state storage?
advantages - durable , fast access times disadvantages - cost , limited read/writes
47
why does data have to be stored in binary form?
All data that we want a computer to process needs to be converted into this binary format.
48
What is a bit?
A binary digit, a 0 or a 1.
49
what is a nibble?
4 bits
50
what is a byte?
8 bits
51
what is a kilobyte?
1000 bytes or 1KB
52
What is a megabyte?
1000 kilobytes
53
what is a gigabyte
1000 megabytes
54
what is a terabyte?
1000 gigabytes
55
What is a petabyte?
1000 terabytes
56
what is a character set?
A defined list of characters recognised by the computer.
57
how is a character set represented?
by a unique binary number
58
what are the well known character sets
ascii extended ascii unicode
59
What is ASCII?
7 bit code that can hold 128 characters
60
What is extended ASCII?
8 bit code that can hold 256 characters
61
What is Unicode?
16 bit code that can hold 65,536 characters
62
how can images be stored?
in binary as bitmaps or vectors
63
What is encoding?
process of converting data into a binary code so that a computer can process it.
64
what is a bitmap image?
an image made of pixels
65
what is a vector image?
An image made with mathematical formulas
66
How is each pixel stored?
in binary
67
how many possible values does 1 bit have?
2 possible values: 0 and 1 , therefore 1 bit can store 2 colours: black and white
68
how many possible values does 2 bit have?
4 possible values: 00,01,10,11 , therefore 2 bit can store 4 colours
69
how do you calculate number of colours?
2n (2 to the power of n ( where n is the number of bits per pixel))
70
what is colour depth?
Number of bits per pixel
71
what is metadata?
Additional data stored with the image to define the width, height, bit depth and colour palette
72
how can resolution and colour depth effect file size?
the greater the resolution and colour depth the larger file size.
73
how many bits does a photograph have?
photograph is stored in 24bit colour depth , each pixel is 24 bits , this is 2 to the power of 24 = over 16 million colours
74
why is analogue sound converted to digital?
so it can be stored in binary
75
what is sound file size?
total number of bits in a sound
76
how do you calculate sound file size?
(number of samples per sec) x (number of bits per sec) x (length of sample in secs)
77
What is bit depth in sound?
number of bits stored per sample
78
how can bit depth affect sound?
the higher the number of bits the greater the quality of the sound and the larger the file size
79
what is sample rate?
the number of samples stored in per second
80
how can sample rate affect sound?
the higher the number of samples per sec , the higher the quality of the sound and the larger the file size

GCSE OCR COMPUTER SCIENCE P1 (3 decks)

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