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IGCSE Computer Science > Chapter 1 - Data Representation > Flashcards

Chapter 1 - Data Representation Flashcards

1
Q

What is the building block of all computers and why

A

Binary number system, because it is only made up of 0’s and 1’s. Computers contain millions of tiny switches that must be in either the ON or OFF position. These positions can be represented by the binary number system.
1=ON(high)
0=OFF(low)

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2
Q

What do switches in a computer do and what is another name for them

A

Make use of logic gates and store and process data
Microtransistors

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3
Q

Whaty does binary allow computers to do

A

Carry out calculations

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4
Q

What is a bit

A

A basic computing element that is either a 0 or 1, comes from BInary digiT

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5
Q

What is the binary number system

A

A number system based on 2, and only contains 0’s and 1’s

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6
Q

What is the denary system also called

A

A base 10 number system

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7
Q

What are the uses of the hexadecimal system (4)

A

Error codes
Mac address
IPv6 adress
HTML colour codes

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8
Q

What are error codes

A

They are codes that are usually automatically generated, and refer to the memory location of the error

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9
Q

What does the MAC address stand for

A

Media Access Control address

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10
Q

What does NIC stand for

A

Network interface card

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11
Q

What is a MAC address

A

A number which uniquely identifies a device on a network, it refers to the NIC.

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12
Q

Why are MAC addresses rarely changed

A

So that a particular device can always be identified no matter where it is

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13
Q

What does the NN-NN-NN in a MAC address identify
What does the DD-DD-DD in a MAC address identify

A

The number of the manufacturer
The device serial number

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14
Q

What do IP addresses stand for

A

Internet protocol addresses

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15
Q

What is the difference between an IPv4 and an IPv6 (2)

A

32 vs 128 bit number. IPv6 uses a colon instead of a decimal point

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16
Q

What does HTML colour codes stand for

A

Hyper text markup language colour codes

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17
Q

What is the maximum denary value of an 8-bit binary number

A

255
(2^8-1)

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18
Q

What is it called when there is more than 8 bits generated after calculations and what does it mean

A

Over flow
The number is too big to be stored in the computer using 8 bits
A bigger register needs to be used

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19
Q

What is an overflow error

A

The result of carrying out a calculation where the result is too big for the computers word size.

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20
Q

hexadecimal

A

A number system based on 16, goes from 0-9 and then A-F

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21
Q

What is HTML

A

It is a mark-up (NOT PROGRAMMING) language used when writing and developing web pages
It uses tags<>
Often represents colours of text on screen

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22
Q

What is a logical shift

A

An operation that shifts buts left/right in a register and replaces shifted bits with 0
Left shift= multiply binary number by 2
Right shift=divide binary number by 2

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23
Q

What is the left most bit reffered to as

A

The most significant bit

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24
Q

ASCII

A

American Standard Code for Information Interchange
It is a set of characters for each character on a standard keyboard and 32 control codes control code. (0-31 denary, 00-19 Hex)
Was used in Communication and computer systems

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25
character set
A set of characters that have been defined by computers hardware and software. It is used so that the computer can understand human characters.
26
What does the standard ASCII code character set consist of and what is it used for
7-bit codes(0-127 in denary/00to 7F in hex) Represent the letters numbers and characters found on a standard keyboard together with 32 control codes(0-31 denary, 00 to 19 hex)
27
What does ASCII vs unicode use to represent a character
1 vs 4 bytes
28
goals of unicode (5)
To have uniform code Unambiguous code Reserve part of the code for private use Universal standard More efficient coding system
29
What is unicode
Character set that represents the languages of the world (first 128 are the same as ASCII)
30
What does the aplitude of a wave specify
The loudness of the sound
31
analouge data
Data that varies continuously
32
How do computers store sound wave data
They convert it from anolouge to digital using an ADC, sampling the amplitude at regular intervals. The amplitude cannot be precicely measured so approximate values are stored.
33
How could you get a more accurately sampled sound
By iincreasing the sampling resolution(bit depth)
34
sampling resolution
Also known as bit depth The number of bits used to represent sound amplitude in a digital recording
35
What is bit depth
The number of bits used to represent the smallest unit in a sound file
36
What is the sampling rate
The number of sound samples taken per second Measured in hertz where 1 herts means one sample per second
37
How is sampling used to record a clip (3)
The amplitude is first determined at set time intervals An approximate representation of the wave is produced Each sample is then encoded to a series of binary digits
38
What are the advantages of a higher sample rate/larger resolution (3)
Larger dynamic range Less sound distortion Better sound quality
39
What are the disadvantages of a higher sample rate/larger resolution (3)
Produces larger file size Takes longer to transmit/download Requires a greater processing power
40
bitmap image
An image made up of pixels
41
What is colour depth
The number of bits used to represent the colours of a pixel
42
What is an image made up of
A two-dimentional matrix of pixels
43
What bit depth do modern computers have
24 bit depth
44
What is image resolution
The number of pixels that make up an image
45
Explain the drawbacks of high resolution images
They increase file sizes, which impacts how many images can be stored on the eg. Hardrive. It takes longer to download and transfer the images.
46
what is pixel density
The number of pixels per square inch
47
How big is a byte
8 bits
48
How big is a nibble
4 bits
49
What is the largest memory size metioned in the texbook
Exabyte X10^18
50
What is a more accurate way of measuring memory sizes, and what should be measured using this
IEC memory size system International electronical commision RAM and ROM
51
Why would data need to be compressed (5)
Storage Time taken to stream Reduce file size=reduce costs Reduce time to download/transmit Reduce bandwidth usage
52
What is bandwidth
Where maximum rate of data transfer accross a network measured in kbps or mbps
53
What is lossy file compression Eg. (3)
A compression process that eliminates unneccesary date and some detail which cannot be recovered during the decompression process JPG MP3 MP4
54
How does lossy file compression affect MP3 (2)
It removes sounds out of the human hearing range If there are 2 sounds at the same time, one is removed
55
What is audio compression
A method used to reduce the size ofa sound file using perceptual music shaping
56
What is the difference between MP3 and MP4 files
MP3 is for music MP4 allows multimedia storage.
57
What is the JPEG file reduction process based on
Human eyes dont detect differences in colour as well as they do differences in brightness By separating pixel colour from brightness, images can be split into 8x8 pixel blocks which allows information to be easily discarded with minimal quality loss
58
When should lossless file compression be used (2)
When comressing large/complex spreadsheets or downloading a large computer application
59
What is RLE and what does it do
Run-length encoding Form of lossless file compression Reduces size of a string of adjacent,identicsl data This string is then encoded into 2 values, the first being the number of identical items in the run, the second the code of the data (eg. ASCII) Only effective if there are long runs of repeated bits
60
What is the left most bit refered to as
The most significant bit
61
What is the right most bit refered to as
The least significant bit
62
Character set
List of characters that have been defined by computer hardware and software, neccessary so that computers can understand human characters. Standard ASCII code character set has 7 bits (0-127 binary, 00 to 7F Hex)
63
Difference between upper and lowercase in ASCII
Upper has the 6th bit as 0, lower as 1 Eg. Uppercase: 0 0 00001 Eg. Lowercase 0 1 00001
64
Extended ASCII
Uses 8 bit codes, gives an extrea 128 codes to allow non-english characters and graphical characters
65
Compression
Reduction of file size through removing repeated or redundant pieces of data (can be lossless or lossy)

IGCSE Computer Science (11 decks)

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