Write a program in C to read the contents of a file, convert them into uppercase and copy to another file using file handling.

Convert File Content to Uppercase and Copy to Another File

This program reads the contents of a file, converts each character into uppercase, and writes the result into another file.

The logic is simple:

• Open source file in read mode
• Open destination file in write mode
• Read each character from source file
• Convert it to uppercase using toupper()
• Write it into destination file

Program

#include <stdio.h>
#include <ctype.h>

int main() {
    FILE fp1, fp2;
    char ch;

    fp1 = fopen("input.txt", "r");
    fp2 = fopen("output.txt", "w");

    if(fp1 == NULL || fp2 == NULL) {
        printf("Error opening file");
        return 0;
    }

    while((ch = fgetc(fp1)) != EOF) {
        ch = toupper(ch);
        fputc(ch, fp2);
    }

    fclose(fp1);
    fclose(fp2);

    printf("Data copied in uppercase successfully");

    return 0;
}

Important Points

• toupper() is used to convert lowercase to uppercase
• Always check if file opened successfully
• EOF means End Of File
• Use fgetc() to read and fputc() to write

Output Example

Input file: hello world
Output file: HELLO WORLD

Final Tip

This is a very common exam question. Focus on logic, not just code memorization.