CAMBRIDGE IGCSE COMPUTER
SCIENCE 0948/0478 SYLLABUS FOR
2024/2025 EXAM REVIEW QUESTIONS
WITH COMPLETE SOLUTIONS
What is a character set - Answer-A representation of characters as numbers. Each
character gets a number. Unicode and ASCII are character sets.
What is ASCII code - Answer-American Standard Code for Information Interchange - it
is used to represent the english alphabet and encodes 128 characters into 7-bit binary
codes
What is Unicode? - Answer-Unicode is used for internal representation of characters
and strings and it uses 16 bits to represent each other.
What are the 2 differences between ASCII code and unicode - Answer-- unicode allows
for a greater range of characters including different languages than ASCII
- unicode requires more bits per character than ASCII
How does a computer represent sound - Answer-a sound wave is sampled so it can be
stored and processed by a computer
What is sampling? - Answer-when an analogue to digital converter converts sound into
a digital form
What is the sample rate - Answer-the number of sample taken in a second
What is the sample resolution - Answer-Number of bits per sample
What happens as the sample rate and resolution increases - Answer-the accuracy of
the recording and the file size increases
What is an image? - Answer-An image is a series of pixels that are converted to binary,
which is processed by a computer
What is the resolution of an image - Answer-the number of pixels in the image
What us the colour depth of an image - Answer-the number of bits used to represent
each colour
What happens as resolution and colour depth increases - Answer-the file size and
quality of the image increases
, How do you calculate file size of an image file - Answer-resolution (width x height) x bit
depth
How do you calculate file size of a sound file - Answer-sampling frequency x bit depth x
length
What are 3 advantages of compression - Answer-- less bandwidth required
- less storage space required
- shorter transmission time
What is lossy compression - Answer-Compression in which some of the information is
permanently removed. E.g. Reducing resolution, colour depth or reducing sample rate
What is lossless compression - Answer-Making the size of a file smaller without
permenantly losing any of the information in the file.
What happens to data to be transmitted - Answer-data is broken down into packets to
be transmitted
What is the structure of a data packet - Answer-a data packet contains a packet header
a payload and a trailer
What is a payload? - Answer-the actual data being sent
What is a trailer - Answer-the end bit of a data being sent
What is the packet header - Answer-a packet header includes
- destination address
- packet number
- originators address
What is packet switching? - Answer-a mode of data transmission in which a message is
broken into a number of packets that are sent independently, over whatever route is
optimum for each packet, and reassembled at the destination.
What is serial data transmission - Answer-where bits are sent one signal at a time over
a single wire allowing high data transfer rates to be achieved
What is parallel data transmission - Answer-where bits are sent simultaneously over a
number of parallel wires
What is simplex data transmission - Answer-Data is sent in one direction only
What is half-duplex transmission? - Answer-where data can travel in both directions
along a single cable but not simultaneously
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