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EnglandComputer Science

Data representation and storage

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do you add two binary numbers, and what does shifting the bits left or right do?

Binary addition of two 8-bit numbers including carrying and overflow, and binary shifts (left and right) and their effect of multiplying or dividing by powers of two.
An Eduqas GCSE Computer Science answer on adding two 8-bit binary numbers (with carrying and overflow) and performing left and right binary shifts, including how a shift multiplies or divides by powers of two.
11 min answer →

How is text stored in binary, and why was Unicode needed when ASCII already existed?

How text is represented using character sets, the ASCII character set, the need for and nature of Unicode, and how a character maps to a binary code.
An Eduqas GCSE Computer Science answer on how text is stored in binary using character sets, the 7-bit ASCII set, why Unicode was needed to support many languages, and how a character maps to a binary code.
9 min answer →

Why is data compressed, and when should you use lossy rather than lossless compression?

The purpose of compression, the difference between lossy and lossless compression, and how to choose the appropriate type for a given scenario.
An Eduqas GCSE Computer Science answer on why data is compressed and the difference between lossy and lossless compression, including run-length encoding and how to choose the right type for a given scenario.
9 min answer →

How do you convert a number between binary, denary and hexadecimal?

Number systems: binary, denary and hexadecimal, and how to convert between all three, including why hexadecimal is used as a shorthand for binary.
An Eduqas GCSE Computer Science answer on the binary, denary and hexadecimal number systems and how to convert between all three, with worked place-value methods and the reason hexadecimal is a useful shorthand for binary.
12 min answer →

How does a computer store a negative whole number in binary?

Signed and unsigned binary, and the use of two's complement to represent negative integers, including converting between two's complement and denary for 8-bit numbers.
An Eduqas GCSE Computer Science answer on signed versus unsigned binary and how two's complement represents negative integers, with worked conversions between 8-bit two's complement and denary in both directions.
10 min answer →

What are the units of data, and how do you calculate the size of an image or sound file?

The units of data (bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte), how images are stored as pixels (resolution and colour depth), how sound is sampled (sample rate and bit depth), and calculating file sizes.
An Eduqas GCSE Computer Science answer on the units of data, how images (resolution and colour depth) and sound (sample rate and bit depth) are represented in binary, and full worked calculations of image and sound file sizes.
12 min answer →