An assignment statement is where you give a new value to a variable. The new value can be a simple constant, as in our first assignment, or an expression which is to be calculated.

count = 99 ;

The thing on the left is the identifier for a variable which we have declared. The equals sign (=) is working as an assignment operator in that it tells the compiler that what follows is an expression which is to be assigned to the variable. In the case of our first assignment the expression is simply the constant 99. When you execute this line of the code, the contents of the count variable change to 99.

The second line is a bit more complicated:

count = count + 1 ;

In this case the expression is a sum which is to be worked out and then assigned to count. The program will fetch the current value of count (which we know is 99) and add 1 to it to produce 100. It will then store the result in count again. The effect of all this is to make count 1 bigger.

/*  Simple Variable  */
void main ( void )
{
  /* create an integer variable  */
  int count ;
  set the value to 99            */
  count = 99 ;
  /* increase count by 1         */
  count = count + 1 ;
}