Loops: Multiplication Table

CSC-115 · Semester I · C Programming

beginner20 minAvailable

Cin-browser interpreter · runs locally

#include <stdio.h>

int main() {
  int n = 7;
  for (int i = 1; i <= 10; i++) {
    printf("%d x %d = %d\n", n, i, n * i);
  }
  return 0;
}

10 lines

Output

Write some code, then press Run. Stdout and errors appear here.

Lab brief

Objective

Generate and print a multiplication table using a for loop, and understand loop control variables.

Theory & concepts

A multiplication table is a classic first loop problem. One for loop iterates a counter from 1 to 10, and each iteration prints one line of the form 'n x i = product'. The counter i is the loop control variable - it drives the loop and is read in every iteration.

Rendering diagram…

The for loop that prints the table

for (int i = 1; i <= 10; i++)
    printf("%d x %d = %d\n", n, i, n * i);

Expected output for n = 5

The program prints exactly ten lines, the first being '5 x 1 = 5' and the last '5 x 10 = 50'. Any missing or extra row means the loop bounds are wrong.

Prerequisites

Lesson: The for loop, break and continue
Lesson: Formatted output with printf

Instructions

1Read an integer n from the user with scanf.
2Use a for loop that runs i from 1 to 10.
3Inside the loop, print 'n x i = n*i' with printf.
4Run with n = 5 and check that 5 x 1 through 5 x 10 appear.
5Modify the loop to print only the even multiples (i = 2; i <= 10; i += 2).

Tasks

Print the full table
Implement the loop so input 5 prints 5 x 1 = 5 through 5 x 10 = 50.
Verify the math
Spot-check two rows with a calculator, e.g. 5 x 7 = 35 and 5 x 9 = 45.
Change the step
Print only even multiples by starting at 2 and stepping by 2.
Reverse it
Print the table in descending order (10 down to 1) with a loop that counts down.

Self-check

All ten rows are printed in the correct order.
Every product is arithmetically correct.
The loop control variable is used correctly and terminates.
The student can change the start, stop, and step of the loop.

Environment

editorstandard inputstdout consoletest cases