The NOT(!) Operators

The NOT(!) Operators

So far we have used only the logical operators && and ||.Third operator is the Not operator, written as !. This operator reverses the result of the expression it operates on.For example,if the expression evaluates to a non-zero value,then applying !operator to it results into a '0'. Vice versa,if the expression evaluates to zero then applying ! operator to it makes it 1,a non-zero value. The result (after applying !) 0 or 1 is considered to be FALSE or TRUE  respectively.  value.The final are Here is an example of the 'NOT' operator applied to a relational expression.!(y=10). The NOT operator is often used to reverse the logical value of a single variable, as in the expression
             if(!flag)
This s another way of saying Does the NOT operator sound confusing?  Avoid it if you want, as the same thing can be achieved without using NOT operator.

Example:30

              main()
              {
               int i=-1,j=1,k,l;
                k=!i&&j;
                l=!i||j;
                printf("%d%d",I,j);
              }

OUTPUT:  0 1



Example:31

          main()
          {
           int x=10,y=5,p,q;
            p=x>9;
            q=x>3&&y!=3;
            printf("p=%d q=%d",p,q);
          }

OUTPUT:  p=1  q=1

Explanation: Since x is greater than  9, the condition evaluates to TRUE, the result of the test is
treated as I otherwise it is treated as 0.Hence p contains value 1.

             q=x>3&&y!=3,

The first  condition evaluates to TRUE,hence is replaced by 1.Similarly,second condition also
evaluates to TRUE and is replaced by 1.Since the conditions are combined using && and since both are TRUE, the result of the entire expression becomes 1,which is assigned to q.


 Example:32

            main()
            {
             int a=30,b=40,x;
              x=(a!=10)&&(b=50);
              printf("x=%",x);
            }

OUTPUT:    x=1

Explanation:  a!=10 evaluates to TRUE and is replaced by 1,b=50 uses an assignment(=), hence 50 is assigned to b. Therefore the condition becomes,
          x=1&&50

       Since 1 and 50 both are TRUE values , x value is '1'

Example:33

               main()
               {
                int a=300,b=10,c=20;
                if(!(a>=400)
                 b=300;
                c=200;
                printf("b=%d c=%d",b,c);
               }

OUTPUT:     b=300 c=200

Explanation:         The condition (a>=400) evaluates to FALSE  since a is neither equal to nor greater than 400.The condition is therefore(!)  negates the result of this condition. This means it reverses the result of condition 0 to 1> thus the IF  gets reduced to,
         if(1)
           b=300;

   obviously, b=300 would get executed, followed by c=200,
 hence the output.       

Example:34

                    main()
                    {
                     int x=10,y=100%90;
                     if(x!=y)
                     printf("x=% y=%d",x,y);
                    }

OUTPUT:    x=10 y=10

Explanation:  Contrary to usual belief, the statement y=100/90
is perfectly acceptable. So the output results.

Example:35

             main()
             {
              int  x=10,y=-20;
              x=!x;
              y=!y;
              printf("x=%d y=%d",x,y):
             }

OUTPUT:          x=0 y=0