Hi!
I'm trying to validate the input as 'A' or 'P' with the following function:
char Get_l(void)
{
//declare local variables
char v_let, clearkbd;

printf("Enter A(for AM) or P(for PM):");
v_let = getchar();
while((clearkbd = getc(stdin))!= EOF && clearkbd != '\n');

//Loop until the user enters either A or P
while(v_let != 'A' && v_let != 'P')
{
printf("The letter you entered is not valid. Please enter \
A(for AM) or P(for PM):");
v_let = getchar();
while((clearkbd = getc(stdin))!= EOF && clearkbd != '\n');

}//end of while

return v_let;

}//End of Get_l

If I test it without any previous data entered, it works great. If there was data entered before, and I type A, I get "invalid" message. Can you help me find the problem?

The best I can recall, all of C's standard input functions are buffered, so they may return junk until the buffer is cleared. I'm also not sure if a char can be used for EOF... I *think* it has be of type int, but I'm still quite rusty with C / C++.

When I played around with C a few years ago, I used something like below to validate input.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

int main(void)	{

   char s[2] = { 0 }, *p;

   do {

      printf("A(AM) or P(PM): ");
      fgets(s, sizeof s, stdin);

      if((p = strchr(s, '\n')) == NULL) {
         while(getchar() != '\n'){} // eat the buffer
      }

   } while(toupper(s[0]) != 'A' && toupper(s[0]) != 'P');   
	 
   return (0);
}

HTH