ASCII, Extended ASCII and Unicode

Introduction

Converting text to binary

Converting text to binary is a simple process. You simply look up the decimal value for the character in the ASCII table below, and then convert that value from decimal to binary, like we did last lesson.

Example – hello

ascii-hello-example

ASCII Table

DO NOT USE THE HEX COLUMN!!!

Click to enlarge

Click to enlarge

ASCII Table

Binary to Text

Converting Binary to Text

Converting from binary to text is nice and simple. You simply convert each binary number to a decimal number and then look up that number on the ASCII table.

ascii-goodbye-example

Practice

Convert these text examples to binary:

a. dog

b. cat

c. mouse

Convert these binary examples to text:

d. 01100101 01100111 01100111

e. 01101000 01100001 01101101

f. 01100011 01101000 01101001 01110000 01110011

ASCII

ASCII

Pros

  • Very easy to read, write and understanding ASCII code, simple for a human being to memorise each character.
  • Small storage and transmission size ( 7 bits for standard ASCII 8bits for extended ASCII)

Cons

Only works for the English language, limited number of special characters.

Extended ASCII

Extended ASCII

As ASCII became more widely used outside of America and into Europe there emerged a need to include French and German letters and accents, and so ASCII was extended from 7 to 8 bits, which allowed a total of 256 characters. This system was used for a while until a system that allowed characters from international alphabets to be used – the Unicode system.

Pros

Allowed the use of more European language characters and accents

Cons

  • 1 bit longer than ASCII so required more storage space
  • Still couldn’t support Eastern alphabets / characters

Unicode

UNICODE

It became clear that a system with a much large number of available characters was required and hence Unicode was invented.

Pros

Millions of different characters available due to the larger number of bits per character ( 16 or 32 bits)

(Take a look at the full list here)

Cons

2 or 4 times more storage space taken up per letter.

All the ASCII printable characters

An example of a few of hundreds of thousands of Unicode characters available

 

Resources