I'm Requested to develop a C program

Thanks for everybody.

I started coding the main function, and i found a lot of difficulties in this. and here's the code.

Code:

 
#include <stdio.h>

// The Maximum Length of BookName is 100 Characters
#define MAXL_BOOKNAME	100

// The Maximum Length of BookAuthor is 50 Characters
#define MAXL_BOOKAUTHOR	50

// The Maximum Length of DATE is 20 Characters
#define MAXL_DATE

// Defining a struct (Mostly Quoted from Hammer)
typedef struct BookRecord
{
	int Book_Id;
   char Book_Name[MAXL_BOOKNAME];
   char Book_Author[MAXL_BOOKAUTHOR];
   char Book_PublishingDate[MAXL_DATE];
   /* we can use "time_t Book_PublishingDate; */

   // return true if the Book is borrowed Is it correct?
	bool Book_Borrowed;
} BookRecord_t; // Why using _t ? (Hammer's Code)

void main()
{
   char value;
   int val;
	printf("What Do you Want to do: ");
   printf("\n1. Encrypt The File.");
   printf("\n2. Decrypt The file.");
   printf("\n3. Add a new Book.");
   printf("\n4. Remove an Existing Book.");
   printf("\n5. Update an Existing Book.");
   printf("\n6. Exit Program.\n");
   val=Integer.parseInt(value); // Error here! how to change char to integer
   // in c?

   scanf(value, "%d"); // is this statement true to input a value?

   switch val {
   	case 1:
      	// What functions to include here?
      break;
      case 2:
      	// What functions to include here?
      case 3:
      	AddRecord() // What parameters to include?
      case 4:
      	RemoveRecord(RecordNum) // I'm not sure about the parameters
      case 5:
      	UpdateRecord(RecordNum) // also i'm not ....
      case 6:
      	exit(); // Can I use this exit function that do exist in stdlib (as
         // stumon said?)
}

I included the questions and i'll be thankful if you can answer any, or add new suggestions, and here are the previous questions that still nobody answered :

1. can I use a global list? (i.e. can encryption/decryption work for global?)

2. Another question arose here since i should use variable length record as Mr. Rog said : While Updating a Record, what will happen if the new record is longer than the old one?

3. What happens If I want to delete a name in a record? (i.e. can i remove or update only one field in a record?)

4. how i can declare a primary key in C or C++?

Waiting for Replies,

Originally posted by BadProgrammer
do you mean that i shouldn't make a function for exiting the program? I'll search this function and understand it better, and if you can help i'll be thankful.

The complete answer is:

Originally posted by Hammer
If you want your own, you could do something like my_exit() or Exit()

or simply use the the standard exit() routine that is already defined in C by including stdlib.c. The syntax is:
exit(int);

The int is passed back to the OS for error checking, normal value is 0.

Walt