Chapter 10: Sample Beginner Programs

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This chapter consolidates everything we've learned so far—data types, control flow, and functions—into practical, real-world examples. Analyzing these programs will build your "computational thinking" in C.

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I. Numerical Logic: Fibonacci Sequence

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The Fibonacci sequence is a classic problem in both iterative and recursive programming.

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#include <stdio.h>

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void print_fibonacci(int n) { long long t1 = 0, t2 = 1, nextTerm;

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printf("Fibonacci Series (%d terms): ", n);
for (int i = 1; i <= n; ++i) {
    printf("%lld ", t1);
    nextTerm = t1 + t2;
    t1 = t2;
    t2 = nextTerm;
}
printf("\n");

}

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int main() { int n = 10; print_fibonacci(n); return 0; }

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II. Mathematical Logic: Prime Number Check

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Finding prime numbers is an essential task in cryptography and algorithm design.

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#include <stdio.h>
#include <stdbool.h>

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bool is_prime(int n) { if (n <= 1) return false; for (int i = 2; i * i <= n; i++) { if (n % i == 0) return false; } return true; }

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int main() { int num = 29; if (is_prime(num)) printf("%d is a prime number.\n", num); else printf("%d is not a prime number.\n", num); return 0; }

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III. Data Logic: Simple Bubble Sort

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Sorting is the process of arranging data in a specific order. Bubble Sort is the simplest sorting algorithm, ideal for learning how nested loops interact with data.

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#include <stdio.h>

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void bubble_sort(int arr[], int n) { for (int i = 0; i < n - 1; i++) { for (int j = 0; j < n - i - 1; j++) { if (arr[j] > arr[j + 1]) { // Swap arr[j] and arr[j+1] int temp = arr[j]; arr[j] = arr[j + 1]; arr[j + 1] = temp; } } } }

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int main() { int data[] = {64, 34, 25, 12, 22, 11, 90}; int n = sizeof(data) / sizeof(data[0]); bubble_sort(data, n);

printf("Sorted array: ");
for (int i = 0; i < n; i++) printf("%d ", data[i]);
printf("\n");
return 0;

}

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IV. Interactive Logic: Calculator with switch

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Building a basic command-line tool reinforces user input handling and selection logic.

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#include <stdio.h>

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int main() { char op; double n1, n2;

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printf("Enter operator (+, -, *, /): ");
scanf(" %c", &op);
printf("Enter two numbers: ");
scanf("%lf %lf", &n1, &n2);

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switch (op) {
    case '+': printf("%.1lf + %.1lf = %.1lf\n", n1, n2, n1 + n2); break;
    case '-': printf("%.1lf - %.1lf = %.1lf\n", n1, n2, n1 - n2); break;
    case '*': printf("%.1lf * %.1lf = %.1lf\n", n1, n2, n1 * n2); break;
    case '/': 
        if (n2 != 0) printf("%.1lf / %.1lf = %.1lf\n", n1, n2, n1 / n2); 
        else printf("Error! Division by zero.\n");
        break;
    default: printf("Error! Invalid operator.\n");
}
return 0;

}

These programs are the foundations for all the complex software systems you will encounter in your career. Practice writing them from memory before moving to more advanced topics.