This lesson explains how computers represent text, sound and images as binary. You will learn about character sets such as ASCII and Unicode, how sound is sampled using sample rate and resolution, and how bitmap images are stored using pixels, colour depth and resolution, along with the effect each factor has on file size and quality.
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Representing text
A character set is an agreed table that gives every character (letters, digits, symbols) a unique binary code so that text can be stored and shared between devices.
ASCII uses 7 bits per character, giving 128 different codes, which is enough for the English alphabet in upper and lower case, digits, and common punctuation.
Unicode uses more bits per character (commonly 16 or more), giving tens of thousands of codes, so it can represent the characters of almost every language in the world plus emoji.
The trade-off is that Unicode text takes up more storage per character than ASCII, but it can represent far more symbols than ASCII can.
Check you've got it
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1. Which statement best describes a difference between ASCII and Unicode?
2. A sound clip is recorded at a sample rate of 8000 samples per second, a sample resolution of 16 bits, and lasts 5 seconds. What is its uncompressed size in bits?
3. An image has a colour depth of 3 bits per pixel. How many different colours can each pixel show?
4. What is the most likely effect of increasing the resolution of a bitmap image?