Sams Teach Yourself C in 21 Days

The Pieces of a C Program: Statements, Expressions, and Operators 67

4

TABLE4.2 C’s binary mathematical operators

Operator Symbol Action Example

Addition + Adds two operands x + y

Subtraction - Subtracts the second x - y

operand from the first

operand

Multiplication * Multiplies two operands x * y

Division / Divides the first operand x / y

by the second operand

Modulus % Gives the remainder x % y

when the first operand is

divided by the second

operand

The first four operators listed in Table 4.2 should be familiar to you, and you should have

little trouble using them. The fifth operator, modulus, might be new. Modulus returns the

remainder when the first operand is divided by the second operand. For example, 11

modulus 4 equals 3 (that is, 4 goes into 11 two times with 3 left over). Here are some

more examples:

100 modulus 9 equals 1

10 modulus 5 equals 0

40 modulus 6 equals 4

Listing 4.2 illustrates how you can use the modulus operator to convert a large number of

seconds into hours, minutes, and seconds.

LISTING4.2 seconds.c: Demonstrates the modulus operator

1: /* Illustrates the modulus operator. */

2: /* Inputs a number of seconds, and converts to hours, */

3: /* minutes, and seconds. */

4:

5: #include <stdio.h>

6:

7: /* Define constants */

8:

9: #define SECS_PER_MIN 60

10: #define SECS_PER_HOUR 3600

11:

12: unsigned seconds, minutes, hours, secs_left, mins_left;

13:

14: int main( void )

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