C Programming Basics: Variables, Loops, and Functions Hands-On

C is a language that, once you learn it, gives you a clear picture of how a computer works under the hood. In this tutorial we will look at four fundamentals of C — variables, conditions, loops, and functions — with examples.

1. Variables and data types

A variable is a named box in memory where we store a value. In C, every variable has a specific type:

int age = 20;          // integer
float gpa = 3.85;      // decimal number
char grade = 'A';      // a single character

printf("Age: %d, GPA: %.2f\n", age, gpa);

Here %d prints an integer and %.2f prints a float to two decimal places.

2. Conditions: making decisions

A program has to make different decisions depending on the situation. That is the job of if-else:

int marks = 78;

if (marks >= 80) {
    printf("Grade: A+\n");
} else if (marks >= 70) {
    printf("Grade: A\n");
} else {
    printf("Needs more effort\n");
}

The program checks the conditions from top to bottom and runs only the block whose condition is true first.

3. Loops: doing the same thing repeatedly

Loops are used to do the same task over and over. Here is an example that prints the numbers 1 through 5:

for (int i = 1; i <= 5; i++) {
    printf("%d ", i);
}
// Output: 1 2 3 4 5

A for loop has three parts — the starting value, the condition to keep going, and the change each time. When you do not know the count in advance, a while loop is more useful.

4. Functions: breaking up your code

Instead of writing the same code repeatedly, we put it in a function and call it as needed:

int sum(int a, int b) {
    return a + b;
}

int main() {
    int result = sum(7, 8);
    printf("Sum: %d\n", result);   // Sum: 15
    return 0;
}

Functions make code clean, reusable, and easy to test.

Practice on your own

• Write a program that checks whether a number is even or odd.
• Find the sum of the numbers from 1 to 100 using a loop.
• Write a function that computes the factorial of a number.

Reading alone is not enough — type out every example yourself and run it. Real learning comes from hands-on practice.