Working with the Cast Operator

Playing with the Cast Operator

In C, you can convert one data type to a different one by prefixing the cast operator to the operand.

The general form of the cast operator is

(data-type)x

Here data-type specifies the data type you want to convert to. x is a variable (or, expression) that contains the value of the current data type. You have to include the parentheses ( and ) to make up a cast operator.

For example, the (float)5 expression converts the integer 5 to a floating-point number, 5.0.

The program in Listing 6.4 shows another example of using the cast operator.
TYPE
Listing 6.4. Using the cast operator.

1:  /* 06L04.c: Using the cast operator */
2:  #include <stdio.h>
3:
4:  main()
5:  {
6:     int x, y;
7:
8:     x = 7;
9:     y = 5;
10:    printf("Given x = %d, y = %d\n", x, y);
11:    printf("x / y produces: %d\n",  x / y);
12:    printf("(float)x / y produces: %f\n",  (float)x / y);
13:    return 0;
14: }

    OUTPUT
    The following output is obtained by running the executable 06L04.exe from a DOS prompt:

    C:\app> 06L04
    Given x = 7, y = 5
    x / y produces: 1
    (float)x / y produces: 1.400000
    C:\app>

    ANALYSIS
    In Listing 6.4, there are two integer variables, x and y, declared in line 6, and initialized in lines 8 and 9, respectively. Line 10 then displays the values contained by the integer variables x and y.

The statement in line 11 prints out the integer division of x/y. Because the fractional part is truncated, the result of the integer division is 1.

However, in line 12, the cast operator (float) converts the value of x to a floating-point value. Therefore, the (float)x/y expression becomes a floating-point division that returns a floating-point number. That's why you see the floating-point number 1.400000 shown on the screen after the statement in line 12 is executed.