TAK - L02

• Digital information in computers

  Computers can store and process information using binary variables. The symbols 0 and 1 usually correspond to different voltage state

  
• Digital information in computers

  Information represented by a sequence of binary 0 and 1 are called discrete information

  Advantages of presenting information in digital form:

  • simplicity of design and construction of electric circuits
  • interference immunity
  • ease of information transmission
• Units of information

  
• SI decimal prefixes, which are multiples of 10, are also used to determine a larger numbers of bytes, but they are also often used incorrectly to mean binary prefixes. Accordingly the International Electrotechnical Commission (IEC) has proposed binary prefixes, which are the number 2
• In CS, we use numeral systems in positional notation, which means that the value of each digit depends not only on itself but also on the position it occupies(each position has a specific numerical weight)
• Signed Magnitude(SM)

  
• Two's complement U2

  • Positive numbers represented as standard as in SM
  • Negative numbers
  • determine the number module
  • negate all bit
  • add 1

  
• An alphanumeric code assigns appropriate numerical values to letters, numbers, punctuation marks, and special characters. In the case of computer systems, we use binary strings

  The most popular:

  • ASCII
  • Unicode
  • EBCDID
• ASCII - American Standard Code for Information Interchange

  • range 0-127(7 bits)
  • letters of the alphabet
  • digits
  • punctuation
  • symbols
  • control commands
• ASCII code is 7 bit and most computers operate on 8-bit bytes.

  One of the standards is ISO-8859, which under 8 bit introduces characteristic letters for a given alphabet

  • ISO-8859-1 - for Western Europe
  • ISO-8859-2 for Central and Eastern Europe
• UNICODE 


  A set of characters intended to cover all the writings used in the world. It assigns the unique number to each character, independent of the platform, program or language used.

  Types:

  • UTF-8
  • UTF-16
  • UTF-32
• EBCDIC

  Extended Binary Coded Decimal Interchange Code

  • eight-bit character encoding used primarily in IBM systems
  • Up to 256 different symbols