# 2. Standard ASCII

You already know that computers can only process binary numbers i.e. "0" and "1".

While this works perfectly well for the computer, imagine how hard it would be to write your essays or emails using only 0s and 1s. How would you know if you had made a spelling mistake? How could you proofread your work?

To solve this, a system had to be developed that would allow computer operators to use the full set of alphabetic characters, both upper and lower case, numbers and symbols.

The system uses binary codes to represent each character, number and symbol in the chosen language.

The most commonly used system is called the 7 bit standard ASCII code short for (The **A**merican** S**tandard **C**ode for **I**nformation **I**nterchange)

7 bits gives you 2^{7} possible values. This is 2 x 2 x 2 x 2 x 2 x 2 x 2, or 128. So the ASCII character set goes from 0-127. The character set is broken down like this :-

Lower case letters of the alphabet | 26 |

Upper case letters of the alphabet | 26 |

Number symbols | 10 |

Punctuation marks and white space | 33 |

Control codes such as carriage return and line feed | 32 |

TOTAL SET |
127 |

Note that there are 127 active characters i.e. show or do something, however code 000 means NUL which means do or show nothing, thus making up the 128 combinations.

**Challenge** see
if you can find out one extra fact on this topic that we haven't
already told you

Click on this link: What is ASCII