Summary - Loops
- C course
- Beginner
- Lesson 47/116
- 5 min
Combine for, while and nested loops to write a multiplication table.
Summary - Loops
In this section you learned for, while, do-while, break, continue and nested loops. Now we'll combine them in a multiplication table app.
The multiplication table is the classic example of nested loops: the outer loop produces rows, the inner produces columns. Then we'll add a while menu loop.
Practice 3x3 multiplication table
Write a C program. Write an outer for (int i = 1; i <= 3; i++) and inner for (int j = 1; j <= 3; j++) loop. In the inner loop print printf("%d ", i * j);. At the end of the outer print printf("\n");. Put #include <stdio.h> at the top.
Starter code
#include <stdio.h>
int main(void) {
// Print a 3x3 multiplication table with nested for
return 0;
}Sample solution
#include <stdio.h>
int main(void) {
for (int i = 1; i <= 3; i++) {
for (int j = 1; j <= 3; j++) {
printf("%d ", i * j);
}
printf("\n");
}
return 0;
}Expected output
1 2 3 2 4 6 3 6 9
Practice 1 to 5 with while
Write a C program. Declare int i = 1;. Use a while (i <= 5) loop to print printf("%d\n", i); and increment with i++;. Put #include <stdio.h> at the top.
Starter code
#include <stdio.h>
int main(void) {
// Declare i, print 1 to 5 with while
return 0;
}Sample solution
#include <stdio.h>
int main(void) {
int i = 1;
while (i <= 5) {
printf("%d\n", i);
i++;
}
return 0;
}Expected output
1 2 3 4 5
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which loop builds a multiplication table?
for (i=1; i<=n; i++)
for (j=1; j<=n; j++)
printf("%d ", i*j);- Single while
- Switch
- Single do-while
- Nested for Correct answer
Explanation: The multiplication table uses nested for loops.
2 End the do-while
do {
scanf("%d", &choice);
} ____ (choice == 1);do {
scanf("%d", &choice);
} while (choice == 1);Explanation: do-while ends with while and a semicolon.
3 Match loop and control
| Term | Meaning |
|---|---|
for |
Counted |
while |
Conditional |
do-while |
At least once |
break |
Exit |