Data Representation
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What is binary?
A number system using only 1s and 0s, used by computers to represent all data and instructions.
Why do computers use binary?
Because computers are made of electronic circuits that have two states: on (1) and off (0).
What is a bit?
A binary digit — the smallest unit of data in computing, either 0 or 1.
What are the units of data from smallest to largest?
• Bit • Nibble (4 bits) • Byte (8 bits) • Kilobyte (KB) • Megabyte (MB) • Gigabyte (GB) • Terabyte (TB)
How do you convert binary to denary (decimal)?
Add up the values of the binary digits that are 1 (e.g., 1010 = 8 + 2 = 10).
How do you convert denary to binary?
Subtract the largest possible binary place values from the number, using 1s and 0s to represent each value.
What is hexadecimal and why is it used?
A base-16 number system (0–9 and A–F). It’s shorter and easier for humans to read than binary.
How do you convert binary to hexadecimal?
Split the binary into 4-bit chunks (nibbles) and convert each to a hex digit.
How do you convert hexadecimal to binary?
Convert each hex digit into a 4-bit binary value.
How are characters represented in binary?
Using character sets such as ASCII or Unicode, where each character is assigned a unique binary code.
What is ASCII?
American Standard Code for Information Interchange — uses 7 bits to represent 128 characters including letters, digits, and symbols.
What is Unicode and how is it different from ASCII?
Unicode can represent many more characters (including non-English symbols), using 16 or more bits — supports global communication.
What is an image made up of?
Pixels — small dots of colour, each represented by a binary value.
What is resolution?
The number of pixels in an image (width × height). Higher resolution = more detail.
What is colour depth?
The number of bits used to represent the colour of each pixel. More bits = more colours.
What is metadata in an image file?
Data about the image, such as resolution, colour depth, and file format.
What affects the file size of a bitmap image?
Resolution and colour depth — more pixels and more colours mean larger files.
How is sound represented in binary?
The computer takes samples of the sound wave at regular intervals and records their amplitude as binary numbers.
What is sample rate?
The number of sound samples taken per second, measured in Hz (e.g., 44,100 Hz).
What is sample resolution (bit depth)?
The number of bits used for each sample — higher bit depth = better quality.
What affects the file size of a sound file?
Sample rate, bit depth, and duration — more of any of these = larger file.
What is data compression?
The process of reducing the size of a file so it takes up less storage and can be transmitted faster.
What are the two types of compression?
• Lossy: Removes some data to reduce size — smaller files, lower quality. • Lossless: No data is lost — original can be perfectly restored.
Give examples of lossy and lossless file types.
• Lossy: MP3 (audio), JPEG (image), MP4 (video) • Lossless: PNG (image), FLAC (audio), ZIP (compressed folders)