All Computer data is numbers. Each character of a text is stored as a number. When you press a key on the keyboard, the keyboard sends a number, corresponding to the key that was pressed.
ASCII (American Standard Code for Information Interchange) the value of any input (Alphabet/Number/Symbol) from the keyboard will be generated.
It takes single Alphabet/Digit/Symbol which is then converted to ASCII value for that particular input. For instance, a capital “T” is represented by 84 and a small “t” is represented by 116.