Index 10 SET: A
Title of the Program: C | File Handling
Objectives
Upon completion of this lab, students will be able to:
• To understand the concepts of file handling and its importance in C programming.
• To use file pointers and functions like fopen() and fclose() to manage files.
• To implement character-level I/O using getc() and putc().
• To implement integer-level I/O using getw() and putw().
• To perform formatted I/O using fprintf() and fscanf().
• To perform block-level I/O for structures using fread() and fwrite().
Requirements
• Computer System: Any standard desktop or laptop computer.
• Operating System: Windows, macOS, or Linux.
• Integrated Development Environment (IDE) / Compiler:
o Dev-C++
o Code::Blocks
o Visual Studio Code with C/C++ extensions
o GCC (GNU Compiler Collection)
Theory
File Handling in C
File handling in C allows programs to interact with files on the disk. This enables persistent storage
of data, meaning the data remains even after the program has finished running. The <stdio.h>
header file provides a set of standard library functions for file I/O.
The FILE Pointer
All file handling functions use a special pointer of type FILE. This pointer, often called a file
handle, is used to communicate with the file and track its position.
Core File I/O Functions
• fopen(): Opens a file and returns a FILE pointer. It takes the file path and mode (e.g., "r"
for read, "w" for write, "a" for append) as arguments. It returns NULL if the file cannot be
opened.
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• fclose(): Closes an open file, saving all data and releasing the file pointer.
• getc(): Reads a single character from the file.
• putc(): Writes a single character to the file.
• getw(): Reads a single integer from the file.
• putw(): Writes a single integer to the file.
• fscanf(): Reads formatted input from a file, similar to scanf().
• fprintf(): Writes formatted output to a file, similar to printf().
• fread(): Reads a block of data (e.g., a structure or an array of structures) from a binary
file.
• fwrite(): Writes a block of data to a binary file.
Procedure
Part 1: Character and Integer I/O
Problem 1: Reading and Writing a Single Character (putc, getc)
Write a C program to ask for a student's grade (e.g., 'A', 'B', 'C') and write it to a file named
grade.txt. Then, read the character back from the same file and display it on the screen.
C Program:
#include <stdio.h>
int main() {
FILE *fp;
char grade;
// Open file in write mode ("w") to write the grade
fp = fopen("grade.txt", "w");
if (fp == NULL) {
printf("Error opening file!\n");
return 1;
}
printf("Enter student's grade (A-F): ");
scanf(" %c", &grade); // Note the space before %c to consume whitespace
putc(grade, fp); // Write the character to the file
fclose(fp); // Close the file
// Open file in read mode ("r") to read the grade
fp = fopen("grade.txt", "r");
if (fp == NULL) {
printf("Error opening file!\n");
return 1;
}
grade = getc(fp); // Read a character from the file
printf("The grade read from the file is: %c\n", grade);
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fclose(fp); // Close the file
return 0;
}
Output (example):
Enter student's grade (A-F): B
The grade read from the file is: B
Problem 2: Reading and Writing a Single Integer (putw, getw)
Write a C program to store a student's roll number in a file named rollno.dat and then read it
back. Use putw() and getw().
C Program:
#include <stdio.h>
int main() {
FILE *fp;
int roll_number;
// Open file in write mode ("w") to write the integer
fp = fopen("rollno.dat", "w");
if (fp == NULL) {
printf("Error opening file!\n");
return 1;
}
printf("Enter student's roll number: ");
scanf("%d", &roll_number);
putw(roll_number, fp); // Write the integer to the file
fclose(fp); // Close the file
// Open file in read mode ("r") to read the integer
fp = fopen("rollno.dat", "r");
if (fp == NULL) {
printf("Error opening file!\n");
return 1;
}
roll_number = getw(fp); // Read an integer from the file
printf("The roll number read from the file is: %d\n", roll_number);
fclose(fp); // Close the file
return 0;
}
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Output (example):
Enter student's roll number: 101
The roll number read from the file is: 101
Problem 3: Reading and Writing string into file (fprintf(), fscanf())
Write a C program to store a string / message into a file.
C Program:
#include <stdio.h>
int main()
{
FILE *ptr;
char msz[] = "We are learning File Handling";
ptr = fopen("nepal.txt", "w");
if (ptr == NULL)
{
printf("Error opening file!\n");
return 1;
}
fprintf(ptr, "%s", msz);
fclose(ptr);
printf("Data written to file. Please check file!\n");
return 0;
} Output :
Data written to file. Please check file!
Part 2: Formatted and Block I/O
Problem 4: Formatted File I/O (fprintf(), fscanf())
Write a C program to input a student's name, roll number, and GPA. Store this data in a file
named student_info.txt using fprintf(). Then, read the data back from the file using
fscanf() and display it.
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C Program:
#include <stdio.h>
int main() {
FILE *fp;
char name[50];
int roll_no;
float gpa;
// --- Writing to the file ---
fp = fopen("student_info.txt", "w");
if (fp == NULL) {
printf("Error opening file!\n");
return 1;
}
printf("Enter student name: ");
scanf(" %[^\n]", name); // Reads until newline, including spaces
printf("Enter roll number: ");
scanf("%d", &roll_no);
printf("Enter GPA: ");
scanf("%f", &gpa);
fprintf(fp, "%s\n%d\n%.2f\n", name, roll_no, gpa); // Separate with
newlines
fclose(fp);
// --- Reading from the file ---
fp = fopen("student_info.txt", "r");
if (fp == NULL) {
printf("Error opening file!\n");
return 1;
}
fgets(name, sizeof(name), fp); // Reads the whole line (including spaces)
fscanf(fp, "%d", &roll_no);
fscanf(fp, "%f", &gpa);
printf("\n--- Student Details Read from File ---\n");
printf("Name: %s\n", name);
printf("Roll No: %d\n", roll_no);
printf("GPA: %.2f\n", gpa);
fclose(fp);
return 0;
}
Output (example):
Enter student name: Kapil Sharma
Enter roll number: 105
Enter GPA: 3.85
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--- Student Details Read from File ---
Name: Kapil Sharma
Roll No: 105
GPA: 3.85
Problem 5: Formatted File I/O-II (fprintf(), fscanf())
Write a C program to define a Student structure with roll_no, name, and gpa. The program
should:
1. Ask the user for the number of students (N).
2. Input details for N students into an array of structures.
3. Write the details of all students to a text file named students.txt using fprintf().
4. Read the data back into a new array of structures using fscanf().
5. Display the details of all students from the newly read array.
C Program:
#include <stdio.h>
#include <stdlib.h>
struct Student {
int roll_no;
char name[50];
float gpa;
};
int main() {
int n, i;
printf("Enter the number of students: ");
scanf("%d", &n);
struct Student students[n]; // Array of structures
// Input student details
for (i = 0; i < n; i++) {
printf("\nEnter details for student %d:\n", i + 1);
printf("Roll No: ");
scanf("%d", &students[i].roll_no);
printf("Name: ");
scanf("%s", students[i].name);
printf("GPA: ");
scanf("%f", &students[i].gpa);
}
// --- Writing to the text file ---
FILE *fp;
fp= fopen("students.txt", "w"); // "w" for write text
if (fp== NULL) {
printf("Error opening file for writing!\n");
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return 1;
}
printf("\nSuccessfully wrote %d student records to students.txt\n", n);
for (i = 0; i < n; i++) {
fprintf(fp, "%d %s %.2f\n", students[i].roll_no, students[i].name,
students[i].gpa);
}
fclose(fp);
// --- Reading from the text file ---
fp= fopen("students.txt", "r"); // "r" for read text
if (fp== NULL) {
printf("Error opening file for reading!\n");
return 1;
}
struct Student read_students[n]; // Array to store the read data
printf("\n--- Student Details Read from Text File ---\n");
for (i = 0; i < n; i++) {
fscanf(fp, "%d %s %f", &read_students[i].roll_no,
read_students[i].name, &read_students[i].gpa);
printf("Student %d:\n", i + 1);
printf("Roll No: %d\n", read_students[i].roll_no);
printf("Name: %s\n", read_students[i].name);
printf("GPA: %.2f\n", read_students[i].gpa);
printf("\n");
}
fclose(fp);
return 0;
}
Output (example):
Enter the number of students: 2
Enter details for student 1:
Roll No: 101
Name: Jenish
GPA: 3.5
Enter details for student 2:
Roll No: 102
Name: Jamuna
GPA: 3.9
Successfully wrote 2 student records to students.txt
--- Student Details Read from Text File ---
Student 1:
Roll No: 101
Name: Jenish
GPA: 3.50
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Student 2:
Roll No: 102
Name: Jamuna
GPA: 3.90
Problem 6: Structure and File I/O (fwrite, fread)
Write a C program to define a Student structure with roll_number, name, and marks. The
program should:
1. Ask the user for the number of students (N).
2. Input details for N students into an array of structures.
3. Write the entire array of structures to a binary file named students.txt using fwrite().
4. Read the data back into a new array of structures using fread().
5. Display the details of all students from the newly read array.
C Program:
#include <stdio.h>
// Define the Student structure
struct Student {
char name[50];
int roll_number;
float marks;
};
int main() {
FILE *fptr;
int i,n;
printf("Enter the Number of students\n");
scanf("%d",&n);
struct Student students[n]; // Array of two student structures
// --- Writing data to file ---
// Open file in binary write mode ("wb")
fptr = fopen("students.txt", "wb");
if (fptr == NULL) {
printf("Error opening file for writing!\n");
return 1;
}
for(i=0; i<n;i++){
printf("Enter details for Student %d:\n",i+1);
printf("Name: ");
scanf(" %[^\n]", students[i].name);
printf("Roll Number: ");
scanf("%d", &students[i].roll_number);
printf("Marks: ");
scanf("%f", &students[i].marks);
}
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// Write the array of structures to the file
// fwrite(&address_of_data, size_of_each_element, number_of_elements,
file_pointer)
fwrite(students, sizeof(struct Student), n, fptr);
printf("\nStudent data written to students.dat successfully.\n");
// Close the file
fclose(fptr);
// --- Reading data from file ---
// Open file in binary read mode ("rb")
fptr = fopen("students.txt", "rb");
if (fptr == NULL) {
printf("Error opening file for reading!\n");
return 1;
}
// Read the array of structures from the file
// fread(&address_of_data, size_of_each_element, number_of_elements,
file_pointer)
fread(students, sizeof(struct Student), n, fptr);
printf("\nReading student data from students.txt:\n");
for (i = 0; i < n; i++) {
printf("Student %d:\n", i + 1);
printf("Name: %s\n", students[i].name);
printf("Roll Number: %d\n", students[i].roll_number);
printf("Marks: %.2f\n", students[i].marks);
printf("---------\n");
}
// Close the file
fclose(fptr);
return 0;
}
Output (example):
Enter the Number of students
3
Enter details for Student 1:
Name: rahul raja
Roll Number: 1
Marks: 33
Enter details for Student 2:
Name: raja ram
Roll Number: 2
Marks: 44
Enter details for Student 3:
Name: ram raja
Roll Number: 55
Marks: 33
Student data written to students.dat successfully.
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Reading student data from students.txt:
Student 1:
Name: rahul raja
Roll Number: 1
Marks: 33.00
---------
Student 2:
Name: raja ram
Roll Number: 2
Marks: 44.00
---------
Student 3:
Name: ram raja
Roll Number: 55
Marks: 33.00
Conclusion
By completing these exercises, I have gained a solid understanding of C file handling. I have
learned how to use various file I/O functions to work with character, integer, and formatted data,
as well as how to perform efficient block-level I/O for complex data types like structures
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