ASCII

• ASCII or American Standard Code for Information Interchange
  • This is an 7 bit code to represent characters.
    • This means that we can represent $2^7 = 128 $ characters.
  • An additional bit was added to allow for parity check.
• ASCII is the basis for character computing today.
  • It has influenced programming language syntax
  • It is why a byte will probably remain an accessible memory size for a long time.
  • It is the basis for unicode
• Originally published in 1963
  • The first part of the code includes a number of control characters
  • It was designed to make sorting easier.
• The standard has been modified a number of times.
• If you look at the code in hex, the organization is clear.
  • 
  • 0x and 1x are control codes
  • 2x are punctuation
  • 3x are the digits
  • 4x and 5x are the upper case letters
  • 6x and 7x are the lower case letters.
  • And other things are stuck in where there is space.
• The control characters have been problematic
  • Systems like windows use return (0D₁₆) or \r and newline (0A₁₆) or \n to mark an end of line.
  • Linux only uses the \n
  • There are similar problems with backspace (08₁₆) and delete ( 7F₁₆)
• Extended ASCII used the 8^th bit to add special characters.