ASCII (American Standard Code for Information Interchange, or ASCII) is actually 7-bit. This means that each ASCII character is represented by 7 binary bits, allowing ASCII to represent 2^7, or 128 distinct characters.
These characters include English uppercase and lowercase letters, digits 0-9, control characters (such as carriage return and line feed), and various punctuation marks and symbols. For example, the ASCII code for uppercase 'A' is 65, with the binary representation being 1000001.
Although ASCII is 7-bit, in practice, 8 bits (a byte) are often used to store each ASCII character. This is because most modern computer systems are based on 8-bit groups (bytes), so when storing, an additional 0 bit is typically added before the 7-bit ASCII code to make it 8 bits or a byte. A primary reason for this is memory alignment, which facilitates computer processing and storage management.
Over time, to meet the needs of more languages and symbols, ASCII has been superseded or supplemented by extended versions and other encoding standards (such as UTF-8 and ISO 8859-1), which support more characters and typically use more bits per character. However, the basic ASCII remains 7-bit.