Introduction to Data Representation

Arithmetic Logic Unit

• everything else in the computer is there to serviice this unit
• Handles Integers.
• Does the calculations.
• may handle floaing point numbers.

 Data Types 

• epresented in binary-coded form
• only have 0&1 to represent everything
• can be classified to these categories:        

1. Numbers used in arithmetic computation
2. Letters of the alphabet used in data processing
3. Other discrete symbols used for specific purpose                    

Alphanumeric Representation

An alphanumeric character set is a set of elements that includes the 10 decimal digits, the 26 letters of the alphabet and a number of special character such as $, +, and =.

1. The standard alphanumeric binary code : ASCII (American Standard Code for Information          Interchange)

• uses seven bits to code 128 characters.
• codes must be in binary because registers can only hold binary information.

2. Another alphanumeric code used in IBM equipment, EBCDIC (Extended BCD Interchange Code) that used 8 bits for each character.

• BCD (Binary Coded Decimal) represents each individual digit of a decimal number as a group of binary bits; the other formats would convert an entire decimal value to its equivalent binary value. *In the 8421 Binary Coded Decimal (BCD) representation each decimal digit is converted to its 4-bit pure binary equivalent.