Broken code(newbie code), Loop not working as intended - c

Question

I am trying to write a program that prompts people to re-enter their name if they put numbers or special characters in them. (Working on numbers first then I will do special characters).
My for loop is not acting as I expected it to. I wanted my for loop to go over every char in name[256], and check if it is a ... z || A ... Z. However, I am running into problems. See output below the code.
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
int main()
{
int age;
int i = 0; //for the loop
float height, weight;
char name[256];
char reason[256];
printf("--------------------------------\n");
printf("WRITE YOUR INFORMATION\n");
printf("--------------------------------\n");
printf("NAME : ");
fgets(name, 256, stdin);
while (name[i] != '\0')
{
if (name[i] != (name[i] >= 'a' && name[i] <= 'z') || (name[i] >= 'A' && name[i] <= 'Z'))
{
printf("Enter your name again, no numbers.\n");
i++;
printf("NAME : ");
fgets(name, 256, stdin);
}
break;
}
printf("AGE :");
return 0;
}
This is when my input for fgets function is br4ndon, sure it worked good, but when i typed in br4ndon again, it passed by... it wasn't supposed to.
--------------------------------
WRITE YOUR INFORMATION
--------------------------------
NAME : br4ndon
Enter your name again, no numbers.
NAME : br4ndon
AGE :
Now this is an input with brandon
--------------------------------
WRITE YOUR INFORMATION
--------------------------------
NAME : brandon
Enter your name again, no numbers.
NAME : brandon
AGE :
How can I make sure that it only prompts to re-enter name if the charachter contains anything but a ... z || A ... Z?

Answer 1

There are many issues in your code:
you mix up the loop for the input of name and the loop that checks if none of the chars of name is anything else than a letter.
you omit the removal of the trailing \n after fgets(read the fgets documentation)
the condition name[i] != (name[i] >= 'a' && name[i] <= 'z') || (name[i] >= 'A' && name[i] <= 'Z') makes no sense at all.
You want something like this:
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
int main()
{
int age;
float height, weight;
char name[256];
char reason[256];
printf("--------------------------------\n");
printf("WRITE YOUR INFORMATION\n");
printf("--------------------------------\n");
while (1)
{
printf("NAME : ");
int nameok = 1;
fgets(name, 256, stdin);
name[strcspn(name, "\n")] = 0; // remove the `\n` at the end of name
for (int i = 0; i < strlen(name); i++)
{
if (!(name[i] >= 'a' && name[i] <= 'z') || (name[i] >= 'A' && name[i] <= 'Z'))
{
// character not included in A..Z or a..z
nameok = 0;
break;
}
}
if (nameok)
break; // name is OK, we end the while loop
// name not OK: ask again
printf("Enter your name again, no numbers.\n");
continue;
}
printf("AGE :");
return 0;
}
There is still room for improvement:
Examples:
you should use isalpha from ctype.h (which you include already) instead of the awkward !(name[i] >= 'a' && name[i] <= 'z') || (name[i] >= 'A' && name[i] <= 'Z') condition.
you should make a function that asks for the name
fgets(name, 256, stdin) should rather be fgets(name, sizeof(name), stdin), so if you change the size of the name array, you only need to change it in one place