Fundamentals: Data Representation

Characters are stored using codes such as ASCII (7-bit) or Unicode (UTF-8, UTF-16). Each letter or symbol has a numeric code which is stored in binary.

Key Definitions

How it works

1. Each character on your keyboard, including letters, numbers, and symbols, is assigned a unique numerical value.
2. The numberical value assigned to each character is standardised by the Character set. To examples of character sets are ASCII (American Standard Code for Information Interchange) and Unicode. ASCII only supports American characters with only 128 possible values using 7 binary digits. Unicode is usually represented in 16 or 32 bits and supports the many different characters avail in all languages and other symbols including emojis
3. For example, the letter 'H' is 72, 'e' is 101, 'l' is 108, and 'o' is 111.
4. These decimal numbers are then converted into binary code (a series of 1s and 0s), which is the language computers understand.
5. When you type "Hello," the device converts it to its binary equivalent, sends it, and the receiving device converts it back into ASCII, displaying the original text.

Interactive 4x4 Image Creator

Choose a colour depth, then a colour, and click on the grid to paint pixels. Binary values update below.

Images are stored as a grid of pixels. Each pixel has a binary value representing its colour, often using RGB values. The number of bits used per pixel is called the colour depth.

Key Definitions

How it works

1. An image is made up of tiny squares called pixels. Each pixel stores a single colour.
2. Each colour is represented using binary. The number of binary digits used per pixel is called the colour depth, this impacts how many colours are available. For greyscale images, each pixel is given a value (e.g. from 0 = black to 255 = white). For colour images, pixels are often stored using the RGB model: Red, Green, and Blue values each range from 0 to 255. Example: (255, 0, 0) = pure red.
   So, a single pixel in RGB needs 3 numbers (Red, Green, Blue), which means: 8 bits for Red + 8 bits for Green + 8 bits for Blue = 24 bits per pixel.
3. The computer stores the binary for each pixel, row by row, like a grid. Extra information (called metadata) is stored too, this includes:
   • Image width and height
   • Colour depth (bits per pixel)
   • File format (e.g. JPEG, PNG, BMP)

Interactive Sound Sampling Demo

Change the sample rate and bit depth to see how digital sound approximates an analogue wave.

Sound is represented by sampling the amplitude of sound waves at regular intervals. The quality depends on the sample rate and bit depth.

Key Definitions

How it works

1. Sound in the real world is analog – it’s a continuous wave of vibrations in the air. Computers can’t store continuous waves directly, so they must convert them into binary.
2. The sound wave is measured (or sampled) at regular intervals. Each measurement records the amplitude (height) of the wave at that point in time. The number of samples taken per second is called the sample rate (measured in Hz).
   Example: CD quality sound = 44,100 samples per second (44.1 kHz).
3. The accuracy depends on the bit depth (number of bits used per sample). Example:
   • 8-bit → 256 possible values
   • 16-bit → 65,536 possible values
   A higher bit depth means the sound is stored more accurately.
4. Each sample value is then converted into binary. All the binary values are stored in sequence, along with extra metadata like:
   • Sample rate
   • Bit depth
   • Number of channels (mono or stereo)