When computers communicate, store data or display texts, everything ultimately boils down to just 0s and 1s. But how do those numbers represent letters, symbols and nowadays even emojis? That's what character encoding systems are used for. ASCII is one of the earliest and one of the most influential character encoding systems.
So what is ASCII?
ASCII stands for American Standard Code for Information Interchange. It is a character encoding standard developed in the early 1960s to represent text in computers, telecommunication equipment and other devices.
In earlier days, manufacturers used different codes to represent characters and special symbols, which made data sharing impossible. Former IBM engineer Bob Bemer submitted a proposal to the American Standards Association to solve this issue by making a single unified language for computers. In 1961 a committee was created to make this a possibility, but it took them two years to complete. The first edition of ASCII was released in 1963.
How does ASCII work?
ASCII assigns a unique numeric value to each character so that computers can store and transmit text consistently.
- A → 65 → 01000001
- a → 97 → 01100001
ASCII is a 7 bit encoding system, which means it can represent up to 128 characters (from 0 to 127)
Categories of ASCII characters
1) Control characters (0 to 31 and 127)
These characters are non-printable and were designed to control hardware and data transmission.
- 0 → Null
- 8 → Backspace
- 9 → Tab
These were especially useful in early computers, printers and teletype machines.
2) Printable Characters (32 to 126)
These characters are visible and commonly used in text. They include:
- Space → 32
- Digits → (48 to 57)
- Uppercase Letters → (65 to 90)
- Lowercase Letters → (97 to 122)
- Special symbols like ! @ $ % etc
Why ASCII become widely used?
1) Standardization
Before ASCII different manufacturers used different encodings, making communication between systems very difficult. ASCII provided a common standard that everyone could use, making communication simple.
2) Simplicity
ASCII was perfect for early computers with very limited memory and processing power because it used fixed size encoding and simple numerical mappings.
3) Efficiency
Using only 7 bits per character saved a lot of memory and money at a time when storage was extremely expensive.
Limitations of ASCII
Despite its popularity, ASCII has significant limitations.
Since ASCII uses 7 bits, it can only represent 128 symbols in total (0 to 127).
So ASCII only supports,
- English Letters
- Some special symbols
- Digits and Control signals
There's no support for accented characters, other language scripts or symbols, which made ASCII unsuitable for global use. There is no way to represent every script and symbol with just 128 codes. These limitations led to the creation of Extended ASCII.
Extended ASCII
Extended ASCII uses 8 bits instead of 7 bits, giving an extra 128 characters, which again is not enough to represent everything, but it was a huge improvement from ASCII. Those extra characters were used to represent accented characters, additional symbols, currency symbols etc.
But unlike ASCII, Extended ASCII was not standardized globally. So different organizations used different versions of Extended ASCII which again led to compatibility problems.
Why does ASCII still matter today?
Even though modern systems use Unicode, ASCII remains deeply embedded in computing.
- UTF-8 is backward compatible with ASCII
- Programming languages use ASCII based syntax
In many ways ASCII is the core subset of modern text encoding.
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