go

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
typedef enum { FALSE, TRUE } Boolean;
Boolean namecheck();
Boolean lastnamecheck();
Boolean idcheck();
void firstoption();
Boolean agecheck();
Boolean Isbigletter(char c);
Boolean Issmallletter(char c);
Boolean Isnumber(char c);
Boolean emailcheck();
Boolean digitcardcheck();
int firstscreen();

int main()
{
	int temp = 0;
	namecheck();
	idcheck();
	temp = firstscreen();
	if (temp == 4)
		return 0;
	else
		if (temp == 1)
	{
		firstoption();
	}



	getchar();

}

Boolean namecheck()
{
	Boolean bool = FALSE;
	char name = 0;
	while (bool == FALSE)
	{
		fflush(stdin);
		printf("Please enter your name\n");
		name = getchar();
		if (Isbigletter(name))
		{
			fflush(stdin);
			name = getchar();
			while (Issmallletter(name))
			{
				fflush(stdin);
				name = getchar();
			}
			if (name == '.')
			{
					return TRUE;
			}
			else
			{
				printf("Invalid character\n");
			}
		}
		else
		{
			printf("Invalid character\n");
		}
	}
}
Boolean lastnamecheck()
{
	Boolean bool = FALSE;
	char name = 0;
	while (bool == FALSE)
	{
		fflush(stdin);
		printf("Please enter your last name\n");
		name = getchar();
		if (Isbigletter(name))
		{
			fflush(stdin);
			name = getchar();
			while (Issmallletter(name))
			{
				fflush(stdin);
				name = getchar();
			}
			if (name == '.')
			{
				return TRUE;
			}
			else
			{
				printf("Invalid character\n");
			}
		}
		else
		{
			printf("Invalid character\n");
		}
	}
}
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 idcheck()
{
	Boolean bool = FALSE;
	char id = 0;
	int counter = 0;
	while (bool == FALSE)
	{
		fflush(stdin);
		printf("Please enter your ID number\n");
		id = getchar();
		counter++;
		if (Isnumber(id))
		{
			fflush(stdin);
			id = getchar();
			counter++;
			while (Isnumber(id))
			{
				fflush(stdin);
				id = getchar();
				counter++;
				if (counter == 9)
				{
					return TRUE;
				}
			}


				printf("Invalid character\n");
				counter = 0;
		}
		else
		{
			printf("Invalid character\n");
			counter = 0;
		}
	}
}
int firstscreen()
{
	int option = 0;
	int illcount = 1;
	printf("Thank you for choosing SCE Internet Company! How can we help you?\n");
	printf("1) I want to join your company as a new client.\n");
	printf("2) I want to find out some details about my already existing account.\n");
	printf("3) I want to leave your company.\n");
	printf("4) I want to exit the chat.\n");
	scanf_s("%d", &option);
	if ((option > 0) && (option < 5))
		return option;
	while (illcount != 0)
	{
		if (((option < 1) || (option > 4)))
		{
			if (illcount < 3)
			{
				illcount++;
				printf("An illegal option! This is the %d time you chose an illegal option\n", illcount - 1);
				printf("Please retry.\n");
				printf("Thank you for choosing SCE Internet Company! How can we help you?\n");
				printf("1) I want to join your company as a new client.\n");
				printf("2) I want to find out some details about my already existing account.\n");
				printf("3) I want to leave your company.\n");
				printf("4) I want to exit the chat.\n");
				scanf_s("%d", &option);
			}
		}
		if (illcount >= 3)
		{
			illcount++;
			printf("Please come back only when you need something. Have a good day!\n", illcount-1);
			getchar();
			getchar();
			return 4;
		}
		if ((option > 0) && (option < 5))
		{
			illcount = 0;
			return option;
		}
	}
	illcount = 0;
	return option;
}
Boolean agecheck()
{
	Boolean bool = FALSE;
	short age = 0;
	while (bool == FALSE)
	{
		fflush(stdin);
		printf("Please enter your age\n");
		scanf_s("%hd" ,&age);
		if ((age > 17) && (age < 121))
		{
			return TRUE;
		}
		else
			printf("Invalid age\n");
	}
}
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");
		}
	}
}
Boolean digitcardcheck()
{
	Boolean bool = FALSE;
	int digit = 0;
	int temp = 1;
	printf("Enter your 4 last credit card digits\n");
	temp = scanf_s("%d", &digit);
	if (temp != 1)
		printf("Invalid character\n");
	while ((digit < 1000) || (digit > 9999))
	{
		printf("Error! Please enter only the 4 last digits\n");
		temp = scanf_s("%d", &digit);
	}
		return TRUE;

}
void firstoption()
{
	lastnamecheck();
	agecheck();
	emailcheck();
	digitcardcheck();
	printf("Thank you for choosing our company and welcome! Our people will contact you shortly!\n");
	firstscreen();
}