ggg

Boolean Isbigletter(char c)
{
	if ((c > 64) && (c < 91))
		return TRUE;
	return FALSE;
}
Boolean Issmallletter(char c)
{
	if ((c > 96) && (c < 123))
		return TRUE;
	return FALSE;
}
Boolean Isnumber(char c)
{
	if ((c > 47) && (c < 58))
		return TRUE;
	return FALSE;
}
Boolean emailcheck()
{
	Boolean bool = FALSE;
	char mail = 0;
	char mailtemp = 0;
	while (bool == FALSE)
	{
		fflush(stdin);
		printf("Please enter your Email address\n");
		mail = getchar();
		if ((mail == '_') || (mail == '.') || (Isnumber(mail)) || (Isbigletter(mail)) || (Issmallletter(mail)))
		{
			fflush(stdin);
			mail = getchar();
			while ((mail == '_') || (mail == '.') || (Isnumber(mail)) || (Isbigletter(mail)) || (Issmallletter(mail)))
			{
				fflush(stdin);
				mail = getchar();
			}
			if (mail == '@')
			{
				fflush(stdin);
				mailtemp = getchar();
				while ((mailtemp == '.') || (Isnumber(mailtemp)) || (Issmallletter(mailtemp)) || (Isbigletter(mailtemp)))
				{
					fflush(stdin);
					mailtemp = getchar();
				}
				if (mailtemp == ' ')
				{
					return TRUE;
				}
				else
					printf("Invalid character\n");
			}
			else
			{
				printf("Invalid character\n");
			}
		}
		else
		{
			printf("Invalid character\n");
		}
	}
}