Fundamental Topic in C Language

Sure! Below is a list of some fundamental C language topics along with detailed examples for each topic:

1. Hello World Program:
   Example:
   ```c
   #include <stdio.h>
   
   int main() {
       printf("Hello, World!\n");
       return 0;
   }
   ```
   This is a basic C program that prints "Hello, World!" to the console.

2. Variables and Data Types:
   Example:
   ```c
   #include <stdio.h>
   
   int main() {
       int age = 25;
       float height = 5.9;
       char grade = 'A';
   
       printf("Age: %d\n", age);
       printf("Height: %.1f\n", height);
       printf("Grade: %c\n", grade);
   
       return 0;
   }
   ```
   This program declares variables of different data types (int, float, char) and prints their values.

3. Input and Output:
   Example:
   ```c
   #include <stdio.h>
   
   int main() {
       char name[50];
       printf("Enter your name: ");
       scanf("%s", name);
   
       printf("Hello, %s!\n", name);
       return 0;
   }
   ```
   This program takes user input (name) and prints a personalized greeting.

4. Conditional Statements (if-else):
   Example:
   ```c
   #include <stdio.h>
   
   int main() {
       int num;
       printf("Enter a number: ");
       scanf("%d", &num);
   
       if (num > 0) {
           printf("Positive number\n");
       } else if (num < 0) {
           printf("Negative number\n");
       } else {
           printf("Zero\n");
       }
   
       return 0;
   }
   ```
   This program checks if a number is positive, negative, or zero using if-else statements.

5. Loops (for, while, do-while):
   Example (for loop):
   ```c
   #include <stdio.h>
   
   int main() {
       int i;
       for (i = 1; i <= 5; i++) {
           printf("%d ", i);
       }
       printf("\n");
   
       return 0;
   }
   ```
   This program uses a for loop to print numbers from 1 to 5.

6. Arrays:
   Example:
   ```c
   #include <stdio.h>
   
   int main() {
       int numbers[5] = {1, 2, 3, 4, 5};
       int i;
   
       printf("Array elements: ");
       for (i = 0; i < 5; i++) {
           printf("%d ", numbers[i]);
       }
       printf("\n");
   
       return 0;
   }
   ```
   This program declares and prints elements of an integer array.

7. Functions:
   Example:
   ```c
   #include <stdio.h>
   
   int add(int a, int b) {
       return a + b;
   }
   
   int main() {
       int num1 = 5, num2 = 3, result;
       result = add(num1, num2);
       printf("Sum: %d\n", result);
   
       return 0;
   }
   ```
   This program defines a function to add two numbers and uses it in the main function.

8. Pointers:
   Example:
   ```c
   #include <stdio.h>
   
   int main() {
       int num = 10;
       int *ptr;
   
       ptr = &num;
   
       printf("Value of num: %d\n", num);
       printf("Address of num: %p\n", &num);
       printf("Value of ptr: %p\n", ptr);
       printf("Value pointed by ptr: %d\n", *ptr);
   
       return 0;
   }
   ```
   This program demonstrates pointers by declaring a variable, a pointer to that variable, and printing their values and addresses.

9. Structures:
   Example:
   ```c
   #include <stdio.h>
   
   struct Student {
       char name[50];
       int age;
       float marks;
   };
   
   int main() {
       struct Student s;
       printf("Enter name: ");
       scanf("%s", s.name);
       printf("Enter age: ");
       scanf("%d", &s.age);
       printf("Enter marks: ");
       scanf("%f", &s.marks);
   
       printf("Student Details:\n");
       printf("Name: %s\n", s.name);
       printf("Age: %d\n", s.age);
       printf("Marks: %.2f\n", s.marks);
   
       return 0;
   }
   ```
   This program defines a structure for a student and stores and prints their details.

10. File Handling (Reading and Writing):
    Example (writing to a file):
    ```c
    #include <stdio.h>
    
    int main() {
        FILE *file = fopen("example.txt", "w");
        if (file != NULL) {
            fprintf(file, "This is a file handling example.\n");
            fclose(file);
            printf("Data written to the file successfully.\n");
        } else {
            printf("Failed to open the file.\n");
        }
    
        return 0;
    }
    ```
    This program demonstrates writing data to a file.

These examples cover various fundamental concepts of the C programming language. As you progress in your C programming journey, you will encounter more advanced topics and techniques to enhance your skills further.