100% C prog to write only పెద్ద అక్షరాలు (uppercase letters) into file and subsequently print the content

/*dedicated to student who asked genuine doubt and made me think*/
/*this program will create a file where only uppercase
 (A-Z) letters get written into the file. the content is later read and
  displayed on to the screen */
#include<stdio.h>
#include<conio.h>
void main()
{
char ch;
FILE *fptr;
fptr=fopen("nayA1601.txt","w");
printf("\n start entering the data: \n ");
ch=getchar();
while(ch!='z')
{
if((ch>=65 &&ch<=92)) //only uppercase letters get written into file
  fputc(ch,fptr);// only this line is inside the if condition
ch=getchar();
}
fclose(fptr);
printf("\n writing is over. lets read now:\n");
fptr=fopen("nayA1601.txt","r");
printf("\n\n start reading the data from the file: \n ");
while(!feof(fptr))
{
ch=fgetc(fptr);
putchar(ch);
}
fclose(fptr);
getch();
}