Text: ASCII and Unicode
Character sets give every character a code. ASCII's 128 codes, Unicode's millions, and the storage trade-off.
Transcript
Computers store text as numbers. A character set gives every character its own code, and that code is stored in binary.
ASCII uses seven bits, giving one hundred and twenty eight codes: letters, digits, punctuation and control characters. Extended ASCII uses eight bits, giving two hundred and fifty six.
In ASCII, capital A is sixty five, and B is sixty six. The codes follow the alphabet. Lower case a is ninety seven, and the digits start at forty eight.
ASCII only has room for the basics. Other alphabets, symbols and emoji need more codes. Unicode solves this by using more bits for each character.
Unicode can use up to thirty two bits per character, so it can represent over a million characters. The first one hundred and twenty eight are the same as ASCII.
The trade off is size. Each character takes more bits, so the same text needs more storage space in Unicode than in ASCII.
A character set turns characters into codes. ASCII is small and simple, and Unicode is bigger, and covers the world.
More in this series
2:41Denary, binary and hexadecimal
Place values, converting denary to binary and back, and why hex is used for bytes.
2:30Binary addition, overflow and shifts
Adding binary numbers with carries, overflow when a ninth bit is needed, and logical shifts as multiply and divide.
2:12Two's complement
Negative numbers in binary: the -128 place value, invert and add one, and reading a signed byte.
1:27Images
Pixels, resolution, colour depth, image file size and metadata.
1:38Sound
Sampling an analogue wave: sample rate, bit depth, quality against file size.
1:50Storage units and file sizes
Bit to pebibyte in steps of 1024, and calculating image and sound file sizes.
1:58Compression
Why files are compressed, lossy against lossless, and run-length encoding step by step.
5:38Unit 1 quiz
Ten questions with a think-time countdown and explained answers.