read_text_file.c

#include<stdio.h>

int main(){
    FILE *ptr1;
    FILE *ptr2; 
    ptr1 = fopen("a.txt", "r");
    ptr2 = fopen("b.txt", "w");

    char c = fgetc(ptr1);
    while(c!=EOF){
        fputc(c, ptr2);
        fputc(c, ptr2);
        c = fgetc(ptr1);
    }
    fclose(ptr1); 
    fclose(ptr2); 
    return 0;
}