Charsets and encoding

What is a character?

A character is a symbol that humans understand - like letters (a, ñ), numbers (3), or punctuation (?).

Computers, however, only understand binary numbers (0 or 1).

So, to represent characters in a computer, we need a mapping between characters and numbers.

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What is a charset (character set)?

A charset (short for "character set") is basically a table that assigns a unique number (a code point) to each character.

For example, in the ASCII charset:

Character	Decimal Code	Binary Representation
a	97	01100001
b	98	01100010
A	65	01000001

So when you type the letter "a", the computer actually stores the number 97 in memory.

Here is the full ASCII charset table

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What is encoding?

An encoding defines how the numbers (code points) from a charset are stored in bytes.

Think of it like this:

• Charset = Dictionary (maps letters to numbers)
• Encoding = Packaging method (decides how to store those numbers in bytes)

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Example with "a"

Let’s look at "a" in several encodings:

Encoding	How "a" is stored (in bytes)	Explanation
ASCII	01100001 → 0x61	Only one byte (97 in decimal). ASCII supports 128 characters.
UTF-8	01100001 → 0x61	Same as ASCII for English letters. UTF-8 is backward compatible with ASCII.
UTF-16	00000000 01100001 → 0x00 0x61	Uses two bytes for basic Latin letters.
UTF-32	00000000 00000000 00000000 01100001 → 0x00 0x00 0x00 0x61	Always uses 4 bytes per character.

So for the same “a”:

Charset	Encoding	Bytes Stored
ASCII	ASCII	0x61
Unicode	UTF-8	0x61
Unicode	UTF-16	0x00 0x61
Unicode	UTF-32	0x00 0x00 0x00 0x61

Why do we need Unicode?

ASCII only covers 128 characters - perfect for English, but not for other languages.

Unicode was created to represent all the world’s characters (like ñ, 你, or 😊).

Unicode assigns a unique number (code point) to every symbol.

For example:

Character	Unicode code point	Decimal
a	U+0061	97
ñ	U+00F1	241
😊	U+1F60A	128522

UTF-8, UTF-16, and UTF-32 are different ways of encoding these Unicode code points.