Von Neumann architecture was first majoranticipated structure for general-purpose computer. However before consideringmain components of von Neumann architecture let us first elaborate term 'computer' as this will help us in considering about von Neumann architecture in logical detail. Computer is described in Oxford dictionary as 'An automatic electronic apparatus for making calculations or controlling operations which are expressible in logical or numerical terms'.
The description clearly categorises computer as an electronic apparatus though first computers were electro-mechanical and mechanical apparatuses. The definition points towards 2 main areas of computer applications too which are computer assisted controls/operations and data processing. Additionalsignificant aspect of definition is fact that computer can execute only those calculations / operations that can be expressed in Numerical or Logical terms. Some of fundamental questions which arise from above description are: How are the control operations and data processing performed by an electronic device such as computer?
Electronic components are used for makingelementary logic circuits which are used to execute calculations.
What is the fundamental function performed by a computer? Basic function implemented by a computer is execution of program. A program is a sequence of instructions that operates on data to implement certain tasks like finding a prime number. Computer controls execution of the program.
What is data in computers? In modern digital computers data is signified in binary form by employing two symbols 0 and 1. These are known as binary digits or bits however data which we deal with comprises numeric data and characters like alphabets A to Z, decimal digits 0 to 9, arithmetic operators (e.g. +,-, etc.), relations operators (e.g. =, > , etc.) and many other special characters (e.g.;,@,{,], etc.). Consequently there has to be a specific mechanism for data representation. Old computers employ eight bits to signify a character. This allows up to 28 = 256 different items to be represented uniquely. This collection of eight bits is termed as a byte. So one byte is used to represent one character internally. Most computers employ two bytes or four bytes to signify numbers (positive and negative) internally. The data comprises the operational data like integer, decimal number etc.