ASCII (American Standard Code for Information Interchange) is a character encoding system that assigns numbers to letters, digits, and symbols so computers can store and exchange text. Each character gets a number from 0 to 127, which means ASCII uses 7 bits to represent 128 different characters. This includes uppercase and lowercase English letters, numbers 0-9, punctuation marks, and control characters like newline and tab.
Why it matters
ASCII was one of the first widely adopted standards for text encoding, and it remains foundational to how computers handle digital information. When you save a plain text file, work with config files, or send data through an API, ASCII encoding is often working behind the scenes. Understanding ASCII helps you grasp why Unicode was created and why character encoding issues sometimes cause strange symbols to appear in text.
How it Works
In ASCII, the letter "A" is represented by the number 65, "B" is 66, and so on. Lowercase "a" is 97. The digit "0" is actually stored as 48, not zero. A space character is 32. When your computer stores the word "Hi", it really stores the numbers 72 and 105 in binary. You can see this relationship between characters and numbers when working with text processing, JSON data, or debugging character-related issues.
Limitations
ASCII only covers English characters and basic symbols. It cannot represent characters from other languages like Chinese, Arabic, or even accented European letters. This limitation led to the development of Unicode, which can represent virtually every character from every writing system in the world.