Overview
Welcome to Week 5 of C programming! This week, we will explore control statements that help in decision-making and iteration. By the end of this tutorial, you will:
- Understand how to use loops (
for, while, do-while) to repeat tasks - Learn how to use conditional statements (
if-else, switch) for decision-making - Utilize the conditional (
?:) operator for compact conditional expressions
Time Breakdown
- Introduction to Loops & Conditionals (10 min)
- Using
for Loops (15 min) - Nested Loops & Multiplication Tables (15 min)
- Working with
if-else and switch (20 min) - Exercises & Q/A (20 min)
1. Understanding the For Loop (15 min)
A for loop is used when the number of iterations is known beforehand.
Example: Print even numbers from 2 to 20
1
2
3
4
5
6
7
8
| #include <stdio.h>
int main() {
for (int i = 2; i <= 20; i += 2) {
printf("%d ", i);
}
return 0;
}
|
Expected Output:
1
| 2 4 6 8 10 12 14 16 18 20
|
Exercise 1: Modify the above program to calculate and print the sum of all even numbers from 2 to 20.
2. Nested Loops & Multiplication Table (15 min)
Nested loops allow us to create tables and patterns.
Example: Multiplication table up to 10x10
1
2
3
4
5
6
7
8
9
10
11
| #include <stdio.h>
int main() {
for (int i = 1; i <= 10; i++) {
for (int j = 1; j <= 10; j++) {
printf("%3d ", i * j);
}
printf("\n");
}
return 0;
}
|
Expected Output:
1
2
3
| 1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
...
|
Exercise 2: Modify the above program to allow the user to specify the table size.
3. Decision Making with If-Else (20 min)
if-else statements help in executing different code blocks based on conditions.
Example: Check if a number is positive, negative, or zero
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
| #include <stdio.h>
int main() {
int num;
printf("Enter a number: ");
scanf("%d", &num);
if (num > 0) {
printf("The number is positive.\n");
} else if (num < 0) {
printf("The number is negative.\n");
} else {
printf("The number is zero.\n");
}
return 0;
}
|
Example Output:
1
2
| Enter a number: -5
The number is negative.
|
Exercise 3: Write a program that checks if an exam score is a pass or fail (passing mark: 50).
4. Switch Statement (15 min)
The switch statement is useful when there are multiple possible conditions.
Example: Identify vowels and consonants
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
| #include <stdio.h>
int main() {
char ch;
printf("Enter a character: ");
scanf(" %c", &ch);
switch(ch) {
case 'a': case 'e': case 'i': case 'o': case 'u':
case 'A': case 'E': case 'I': case 'O': case 'U':
printf("It is a vowel.\n");
break;
default:
printf("It is a consonant.\n");
}
return 0;
}
|
Example Output:
1
2
| Enter a character: a
It is a vowel.
|
Exercise 4: Write a program that acts as a basic calculator using switch.
5. Conditional Operator (10 min)
The conditional (?:) operator provides a compact way to write if-else statements.
Example: Check if a number is positive, negative, or zero
1
2
3
4
5
6
7
8
9
10
| #include <stdio.h>
int main() {
int num;
printf("Enter a number: ");
scanf("%d", &num);
printf("%s\n", num > 0 ? "Positive" : num < 0 ? "Negative" : "Zero");
return 0;
}
|
Example Output:
1
2
| Enter a number: 7
Positive
|
Exercise 5: Write a program that finds the largest of two numbers using the conditional operator.
Bonus Challenge: Print a Right-Angled Triangle Pattern
Example:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
| #include <stdio.h>
int main() {
int n;
printf("Enter number of rows: ");
scanf("%d", &n);
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= i; j++) {
printf("* ");
}
printf("\n");
}
return 0;
}
|
Example Output (for n = 5):
1
2
3
4
5
| *
**
***
****
*****
|
Summary & Wrap-Up (10 min)
This week, we covered:
- Using loops to automate repetitive tasks
- Making decisions with
if-else and switch - Writing concise conditions with the
?: operator
Next Week: Functions and Modular Programming
Happy coding! 🚀