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Unit 1: Data representation and data types

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

Why do computers use the binary number system, and how do you convert between binary and denary?

The binary and denary number systems, why computers store data in binary, the units of data capacity, and converting whole numbers between binary and denary.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on binary and denary numbers, covering why computers use binary, bits bytes and the units of data capacity, place value in base 2, and converting whole numbers between binary and denary in both directions.
8 min answer →

How do you add binary numbers, what is overflow, and how does an arithmetic shift multiply or divide a binary number?

Adding two binary numbers using the carry rules, the meaning of overflow, and using arithmetic (binary) shifts to multiply and divide by powers of two.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on binary arithmetic, covering adding two binary numbers with the carry rules, the meaning and cause of overflow, and using left and right arithmetic shifts to multiply and divide a binary number by powers of two.
8 min answer →

How are text characters stored in a computer using character sets such as ASCII and Unicode?

Representing characters in binary using character sets, the ASCII and Unicode character sets, and the relationship between a character, its character code and the number of bits needed.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on representing text, covering character sets, the ASCII character set and its size, the Unicode character set and why it was introduced, character codes, and how the number of bits limits the number of characters.
8 min answer →

Why is data compressed, and how do lossy and lossless compression, including run-length encoding, work?

The need for compression, the difference between lossy and lossless compression, and how run-length encoding compresses data.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on compression, covering why data is compressed, the difference between lossy and lossless compression and when each is used, and how run-length encoding (RLE) compresses repeated data with a worked example.
8 min answer →

What is hexadecimal, why is it used in computing, and how do you convert between hexadecimal, binary and denary?

The hexadecimal number system, why hexadecimal is used as a shorthand for binary, and converting between hexadecimal, binary and denary.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on hexadecimal, covering the base 16 number system, why hexadecimal is a convenient shorthand for binary, and converting between hexadecimal, binary and denary in both directions with worked examples.
8 min answer →

How are bitmap images stored in binary, and how do resolution and colour depth affect file size?

Representing bitmap images as pixels, the meaning of resolution and colour depth, calculating the file size of an image, and the role of metadata.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on representing images, covering bitmap images and pixels, resolution, colour depth and the number of colours, calculating image file size from dimensions and colour depth, and the role of metadata.
9 min answer →

How are negative whole numbers stored in binary using sign and magnitude and two's complement?

Representing signed (negative and positive) integers in binary using the sign and magnitude method and the two's complement method, and converting between them.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on representing signed integers in binary, covering the sign and magnitude method, the two's complement method, how to find a two's complement number, and the advantages of two's complement for arithmetic.
9 min answer →

How is analogue sound converted into binary, and how do sample rate and bit depth affect quality and file size?

Representing sound in binary by sampling an analogue wave, the meaning of sample rate and sample resolution (bit depth), and how they affect sound quality and file size.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on representing sound, covering analogue to digital conversion by sampling, sample rate and sample resolution (bit depth), how each affects sound quality and file size, and calculating the file size of a sound recording.
8 min answer →