Chapter 4: Control Flow – if, else, and Loops

Table of Contents

• Table of Contents
• 4.1 if and else Statements
• 4.2 Loops: while, for, do-while
• 4.3 Exercises
• 4.4 Solutions
• 4.5 What’s Coming in the Next Chapter

4.1 if and else Statements

Control the flow of your program using if and else:

if (x > 0) {
    printf("Positive\n");
} else {
    printf("Not positive\n");
}

4.2 Loops: while, for, do-while

Loops let you repeat actions:

• while loop:

  int i = 0;
  while (i < 5) {
    printf("%d\n", i);
    i++;
  }
  

• for loop:

  for (int j = 0; j < 5; j++) {
    printf("%d\n", j);
  }
  

• do-while loop:

  int k = 0;
  do {
    printf("%d\n", k);
    k++;
  } while (k < 5);
  

4.3 Exercises

1. Write a program that prints numbers 1 to 10 using a loop.
2. Modify the program to print only even numbers.
3. What is the difference between while and do-while?

4.4 Solutions

4.4.1 Solution 1

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

4.4.2 Solution 2

for (int i = 2; i <= 10; i += 2) {
    printf("%d\n", i);
}

4.4.3 Solution 3

while checks the condition before the loop body; do-while checks after.

4.5 What’s Coming in the Next Chapter

Next, you’ll learn how to organize your code with functions!

Next Chapter → Functions – Divide and Conquer