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IGCSE Computer Science
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IGCSE Computer Science IGCSE Computer Science IGCSE Computer Science
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IGCSE Computer ScienceAs humans, we process ........data, but a computer cannot process this type of data. For a computer to
be able to process data it needs to be converted to ............data. As humans, we mostly use a ............
number system; this is a base ........ number system. Computers use a .............number system; this is a
base ..........number system.
Complete the sentence by using these words:
denary, 2, 10, binary, analogue, digital - ANS analogue
digital
denary
10
binary
2
Explain why binary is used to store data in a computer system. - ANS Computer consist of transistors /
logic circuits
... that can only store/process data in two states / as high-low / on-off / 1 and 0
Convert 1001 1011 to denary - ANS 128+16+8+2+1= 155
Convert 85 to binary - ANS 1010101
How many bits is in nibble and byte? - ANS 1nibble=4 bits
1 byte=8 bits
How many bytes in a kilobyte? - ANS 1024 bytes
,Explain the differences between the binary system and the denary sytem. - ANS -The Binary number
system is base 2
-The Denary number system is base 10
-The Binary number system uses 0 and 1 values
-The Denary number system uses values from 0 to 9
-The Binary number system has units / placeholders / column headings that increase by the power of 2
-The Denary number system has units / placeholders / column headings that increase by the power of
10
-Binary has more digits for the same value OR Denary has fewer digits for the same value
What is hexadecimal? - ANS Base 16 number system
Convert the hexadecimal number B5 into binary. - ANS 1011 0101
Convert the binary number 1111 0110 into hexadecimal. - ANS F6
What is the advantage of using hexadecimal numbers? - ANS -They are easier to read and understands
-They make it easier to spot mistakes
-They are shorter / More can fit on the screen / 16 bits can be represented by 4 hex digits
-It is easy to convert between Hex and Binary.
-Faster than binary for entering numbers
What is a MAC address? - ANS A Media Access Control (MAC) address is a number that uniquely
identifies a device on the internet.
--> (first part manufacturer ID) (second part serial number)
,For example 23-45-97-89-AB-CD
first 6/8 digits = manufacturer code/ID of device (NIC)
last 6/8 digits = serial number of device (NIC)
It is a static address - It does not change
How hexadecimal is used to display ASCII/Unicode values? - ANS Everytime you type something on your
keyboard for example "A" it will store the ascii value of 65.
Use of hexadecimal in HTML/CSS colour code. - ANS The 6 digit hex colour code should be considered in
three parts.
First two digits represents the amount of red in the colour (max FF, or 255)
The next two digits represent the amount of green in the colour (max FF, or 255)
The final two digits represent the amount of blue in the colour (max FF, or 255)
E.g. orange can be represented as #FFA500, which is (255 red, 165 green, 0 blue).
Give an example of file format. - ANS Sound - .mp3 .wav
Text- .txt .pdf
Picture- .jpeg .png .gif
Video- .mp4
What is a MIDI file? - ANS Musical Instrument Digital Interface (MIDI) s contain a list of commands that
instruct a device how to produce a particular sound or musical note.(set of commands instruction how
the song should be played)
*MIDI files stored the notes played and not the sound.
, e.g.
Durations of note
The volume of the note
Tempo
Type of instrument
Pitch of the note
Modulations
What are 2 types of file compression? - ANS Lossy and Lossless
What is lossy compression? - ANS Compression in which some of the information is permanently
eliminated
What is lossless compression? - ANS Making the size of a file smaller without losing any of the
information in the file.
How image file like jpeg reduce the file size? - ANS JPEG is an image file that used lossy compression to
reduce the size of the file. It reduces the range of colour used/colour depth/bits per pixel and reduces
the number of pixels / removes unnecessary data.
How mp3 reduce the file size? - ANS The mp3 file should use a lossy compressed file. It compresses by
discarding any unnecessary sounds and sounds that humANS can't hear by reducing the rate of the
amplitude of the sounds.
How mp4 reduce the file size? - ANS The mp4 file is suitable to use lossy compressed files. It compresses
by reducing resolution and colour palette that is indistinguishable, so each pixel requires fewer bits and
removes the detail that is unnecessary, like sound that humANS can't hear.
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