how to combine registration and billing for the program - c

Question

the code is register and billing for the hospital that use for some program I can't combine the code together and it could construct program that register and count for the bill that count that
#include <stdio.h>
#include <stdlib.h>
int check_pass(int pass);
int main()
{
int x,pass;
for(x=0;x<5;x++){
printf("Enter your password: ");
scanf("%d",&pass);
check_pass(pass);
if(pass==1234){
break;}
}
return 0;
}
int check_pass(int pass)
{
if(pass == 1234){
printf("Password is correct\n");
printf("============== Hospital City =============== ");
}
else{
printf("Password is wrong, please try again\n");
}
return 0;
}
the another code is for billing for patient that program thank for the help but the code is very blurred for me
#include <stdio.h>
#include <stdlib.h>
int main()
{
int id,day1,mnth1,year1,day2,mnth2,year2;
int days,Bill;
printf("ID: ");
scanf("%d",&id);
printf("Date in (MM/DD/YYYY): ");
scanf("%d/%d/%d",&mnth1,&day1,&year1);
printf("Date out (MM/DD/YYYY): ");
scanf("%d/%d/%d",&mnth2,&day2,&year2);
days = day2 - day1;
printf("Number of days: %d days\n",days);
Bill = days*10;
printf("Bill to pay:%d x RM10 = RM%d\n",days,Bill);
return 0;
}

Answer 1

Bit of an unclear question, but I will attempt to answer.
Break your code into modules. This means, put functionality into functions and not in main. Then, you can call them whenever from wherever.
int get_bill()
{
int id,day1,mnth1,year1,day2,mnth2,year2;
int days,Bill;
printf("ID: ");
scanf("%d",&id);
printf("Date in (MM/DD/YYYY): ");
scanf("%d/%d/%d",&mnth1,&day1,&year1);
printf("Date out (MM/DD/YYYY): ");
scanf("%d/%d/%d",&mnth2,&day2,&year2);
days = day2 - day1;
printf("Number of days: %d days\n",days);
Bill = days*10;
printf("Bill to pay:%d x RM10 = RM%d\n",days,Bill);
return Bill;
}
You can then call this from main after the user enters a password.