How to read and write Huge files with GMP ? I need great processing of data in files as binary

Code:

#include <stdio.h>#include <gmp.h>int main(void){FILE * fr, * fw; // two file pointers prepared for creationchar filename[100]; // a string for file name of input and output filesprintf("Enter file's name : ");scanf("%s", filename); // taking file name of inputfr = fopen(filename, "rb+"); // opening file fr for reading as binaryprintf("Enter copied filename :");scanf("%s", filename); // taking file name of outputfw = fopen(filename, "wb+"); // opening file fw for writing as binarympz_t x; // a big integer decalredmpz_t y; // also ympz_init(x); // initialization of x to 0mpz_init(y); // also ygmp_fscanf(fr, "%Zd", y); // file scanning of input file as huge decimal and store it in ympz_set(x, y); // assigning y in x --- or should it be as a must an explicit number and not variable ?gmp_fprintf(fw, "%Zd", x); // writing x to a filempz_clear(x); // clearing and emptying xmpz_clear(y); // also yfclose(fr); //closing frfclose(fw); // closing fwreturn 0;}