File handling in C means storing data in a file and reading it later using functions from stdio.h. It helps save data permanently (even after the program ends).

• FILE is a structure in C that represents a file.
• fp is a file pointer that will point to the file you want to read/write

Basic steps:

1. Create a file pointer → FILE *fp;
2. Open file → fopen()
3. Read/Write data → fprintf(), fscanf()
4. Close file → fclose()

Program using fprintf() to  write readable characters in the  dat file.

#include <stdio.h>
int main() {
FILE *fp;
char name[50];
char address[100];

// Open file in write mode
fp = fopen(“student.dat”, “w”);

//checking file opening or not if incase of system resource failure
if (fp == NULL) {
printf(“Error opening file!”);
return 1;
}

// values from user input
printf(“\nEnter name and address of the student:”);
scanf(“%s%s”, name,address);

// Write to file
fprintf(fp, “Name: %s\n Address: %s”, name, address);
}
fclose(fp);
printf(“\nData stored successfully in student.dat”);

return 0;
}

Program using fwrite() to  write machine readable  binary blocks in the  dat file.

#include <stdio.h>
int main() {
FILE *fp;
char name[50];
char address[100];

// Open file in binary write mode
fp = fopen(“student.dat”, “wb”);

// checking file opening
if (fp == NULL) {
printf(“Error opening file!”);
return 1;
}

// values from user input
printf(“\nEnter name and address of the student: “);
scanf(“%s %s”, name, address);

// Write to file using fwrite
fwrite(name, sizeof(char), 50, fp); //syntax fwrite(variable, sizeof(variable), 1, filepointer);
fwrite(address, sizeof(char), 100, fp);

fclose(fp);
printf(“\nData stored successfully in student.dat”);
return 0;
}

write a program to enter name and salary of employee and write it in a .txt file using structure

#include <stdio.h>
struct employee {
char name[50];
float salary;
};

int main() {
FILE *fp;
struct employee e;

// Open file in text write mode
fp = fopen(“employee.txt”, “w”);

if (fp == NULL) {
printf(“Error opening file!”);
return 1;
}

// Take input
printf(“Enter employee name: “);
scanf(“%s”, e.name); // read full name with spaces

printf(“Enter salary: “);
scanf(“%f”, &e.salary);

// Write data to text file
fprintf(fp, “Name: %s\nSalary: %.2f\n”, e.name, e.salary);
fclose(fp);
return 0;
}

Write a c program to read from file:

• If your file already exists and contains the line:
• my name is Rajesh Parajuli

#include <stdio.h>
int main() {
FILE *fp;
char word[50];

fp = fopen(“file.txt”, “r”);
if (fp == NULL) {
printf(“Error opening file!\n”);
return 1;
}

while (fscanf(fp, “%s”, word) != EOF) {
printf(“%s “, word); // print each word
}

fclose(fp);
return 0;
}