A character is a single letter, or number, or space, or symbol.
A text file contains nothing but a series of numbers, where each number
represents a character. The number is the character code, which is a mapping
To decode the numbers in a text file, you must know the mappings between those numbers and the characters they represent. Today there is effectively one standard code for this, called Unicode. The first 126 characters in that code are very common and, historically, were defined first as the ASCII code.
Some characters have special “non-printable” meanings and represent something other than a shape you can see: these are called control characters.
Accessing character codes programmatically
Most general programming languages let you access a character’s underlying character code.
In Python, use the
letter = "A" ord(letter) # => 65
In Java, the underlying value of the primitive type
char is its character code.
So casting it explicitly as an integer will give that code. For example:
char letter = 'A'; int char_code = letter; // => 65
charCodeAt() with the index of the character
within the string (but for full Unicode support, use
charCodeAt() is only good for codes up to 65536):
let letters = "ABCZ"; letters.charCodeAt(0); // A => 65 letters.charCodeAt(3); // Z => 90