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Arithmetic operators

Learn basic arithmetic with +, -, *, / and %.

Arithmetic operators

C uses five arithmetic operators often: +, -, *, / and %. The first four are the addition, subtraction, multiplication and division you know. % gives the remainder of a division.

17 % 5  /* 2: 17 = 3*5 + 2 */
7 / 2   /* 3: integer division */

When two int values are divided the fraction is dropped; the result is still an int. Use double if you need the fraction.

Integer division

When two int values are divided the result is an int and the fraction is dropped. 7 / 2 gives 3, not 3.5. This is called integer division.

int a = 7 / 2;   /* a = 3 */
double b = 7.0 / 2.0;  /* b = 3.5 */

For a fractional result make at least one side a double. Writing the literal as 7.0 is enough.

Practice Print five operations

Define int a = 7, b = 3;. With five printf calls print a + b, a - b, a * b, a / b and a % b on separate lines. Output should be 10, 4, 21, 2, 1.

Starter code

main.c
#include <stdio.h>

int main(void) {
    int a = 7, b = 3;
    /* print a + b, a - b, a * b, a / b, a % b */
    return 0;
}

Sample solution

main.c
#include <stdio.h>

int main(void) {
    int a = 7, b = 3;
    printf("%d\n", a + b);
    printf("%d\n", a - b);
    printf("%d\n", a * b);
    printf("%d\n", a / b);
    printf("%d\n", a % b);
    return 0;
}

Expected output

10
4
21
2
1

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is the result of 17 % 5?

  • 3
  • 2 Correct answer
  • 12
  • 0

Explanation: 17 = 3*5 + 2, so the remainder is 2.

2 Complete the remainder operator

Question 
int r = 17 ____ 5;  /* remainder: 2 */
Answer 
int r = 17 % 5;  /* remainder: 2 */

Explanation: The % operator gives the remainder.

3 Match operators to their meanings

Term Meaning
+ Addition
- Subtraction
* Multiplication
/ Division

All lessons in Beginner

1 C basics

  1. What is C?
  2. Your first program
  3. Compile and run
  4. Comments
  5. printf and escapes
  6. Summary - C basics

2 Variables

  1. Declaring variables
  2. Variable assignment
  3. const
  4. Variable scope
  5. typedef
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. char
  4. sizeof
  5. Type conversion
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Menu loop
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Bitwise operators
  6. Summary - Operators

6 I/O

  1. printf formatting
  2. scanf
  3. Multiple inputs
  4. getchar and putchar
  5. puts and fputs
  6. Summary - I/O

7 Conditionals

  1. The if statement
  2. else and else if
  3. The switch statement
  4. The ternary operator
  5. Nested conditionals
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. break and continue
  5. Nested loops
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding products
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Array size
  4. Multidimensional arrays
  5. Arrays and loops
  6. Summary - Arrays

11 Strings

  1. String basics
  2. String literals
  3. strlen
  4. strcpy and strcat
  5. strcmp
  6. Summary - Strings

12 Functions

  1. Defining functions
  2. Return values
  3. Parameters
  4. Function prototypes
  5. Recursion
  6. Summary - Functions

13 Pointer basics

  1. What is a pointer?
  2. The & address operator
  3. Pointer dereference
  4. NULL
  5. Pointer arithmetic
  6. Summary - Pointer basics

14 Arrays and pointers

  1. Array name as pointer
  2. Pointer to array
  3. Passing arrays to functions
  4. Pointer loop
  5. Multidim array pointer
  6. Summary - Arrays and pointers

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String functions

  1. strchr
  2. strstr
  3. strtok
  4. sprintf
  5. sscanf
  6. Summary - String functions

17 Structs

  1. Defining structs
  2. Using structs
  3. typedef struct
  4. Array of structs
  5. Nested structs
  6. Summary - Structs

18 Memory and stack

  1. Stack and heap
  2. Automatic storage
  3. malloc
  4. free
  5. calloc and realloc
  6. Summary - Memory and stack

19 Preprocessor

  1. #define
  2. #include
  3. Conditional compilation
  4. Macro functions
  5. Header files
  6. Summary - Preprocessor

20 Beginner final

  1. Project design
  2. Data model
  3. Functions
  4. Memory management
  5. Putting it together