Unicode

Unicode is a character set standard designed to cover every writing system in the world, along with symbols such as maths signs, music notes and emoji. Each character in the set has its own unique binary code, so the same code stands for the same character on any device.

More bits means more characters

Unicode gives each character more bits than ASCII does. A version of Unicode that uses 16 bits per character has 2 to the power 16, which is 65,536 different codes, so it can hold many thousands of characters. ASCII's 8 bits stretch only to 2 to the power 8, which is 256 codes, so ASCII is limited to English letters, digits, punctuation and a few extra symbols.

Working alongside ASCII

For any character that appears in both sets, Unicode uses exactly the same code as ASCII. Text made of ASCII characters therefore keeps its meaning when it is read as Unicode, so older files and programs carry on working. Unicode is the larger, more capable set, but it does not throw ASCII away.

One benefit and one drawback

The main benefit is that one standard can store text in any language on any device. A birthday message that ends with a waving-hand emoji, or a name that includes an accented letter, saves and displays correctly whatever computer it is opened on.

The main drawback is storage. Because every character uses more bits, the same piece of text takes up more space in Unicode than it would in ASCII, so files and messages become larger.