Data Representations and Databases

Data Representations
Discrete elements of information are represented in a digital system by physical quantities called signals such as voltage and currents are the most common. The signals in all present-day electronic digital systems have only two discrete values and are said to be binary. The digital-system designer is restricted to the use of binary signals because of the lower reliability of many-valued electronic circuits. For example, to translate unsigned binary integers to decimal: 
   dec = (Dn-1×2n-1) + (Dn-2×2n-2) + … +(D1×21) + (D0×20)
Each digit Dj is multiplied by 2j . For example, the decimal equivalent of the binary number (11010)2 can be found from the multiplication of the digits by powers of 2: 
   (11010)2 = 

            = (  )10          
Databases
A database is an organized collection of structured information, or data, typically stored electronically in a computer system. A database is usually controlled by a database management system (DBMS). Together, the data and the DBMS, along with the applications that are associated with them, are referred to as a database system, often shortened to just database.


Review: Data Representation
    What is the decimal value of the bit string: 00101101?

      23
      31
      45
      57
Result:        




      At a party, a young wife admonished her husband,    
      “That’s the fourth time you’ve gone back for ice cream and cake.    
      Doesn’t it embarrass you?”    
      “Why should it?” answered her spouse.    
      “I keep telling them it’s for you.”    
      — Selma Glasser, Good Housekeeping