File To UpperCase Using Command line

PROGRAM CODE:-

#include<stdio.h>
int main(int n,char *a[]) {
    int c;
    FILE *fr, *fw;

    if(n != 3){
        printf("Invalide numbers of arguments.");
        return 1;
    }

    if((fr = fopen(a[1], "r")) == NULL) {
        printf("File can't be open.");
        return 1;
    }
    if((fw = fopen(a[2], "r+")) == NULL) {
        printf("File can't be open.");
        fclose(fr);
        return 1;
    }
    while(1) {
        c = fgetc(fr);
        if (feof(fr)) break;
        c = ~c;
        fputc(c, fw);
    }
    fclose(fr);
    fclose(fw);
    return 0;
}