Airline Reservation System

This is my project done for Delhi Technological University (formerly, Delhi College of Engineering), Faculty of Information Technology for a beginner course in Programming Fundamentals in C (Course Code - CO101).

A basic implementation of Airline Reservation System in C language using the concept of Structures and Data File Handling.

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Documentation

Definition - An airline reservation system contains details about flight schedules and its flight tariffs, passenger reservations and ticket records.

Problem Statement - The task is to create an airline reservation system which can perform the following operations:

1. Add new records.
2. List records.
3. Search records
4. Modify records.
5. Change flight rates.
6. Delete records.

Approach - The idea is to write individual block of code for every operation. All the blocks of code are unified together to form the main program.

Following caveats would help to understand the program easily:

• Add new records - Addition of records must always take place at the end of the existing records in the file, much in the same way you would add new records in a register manually.
• List records - Listing records means displaying the existing records on the screen. Naturally, records should be listed from first record to last record.
• Search records - To perform searching, we ask the user to enter the name of the person whose record is to be searched and then match it with the information stored in the binary file.
• Modify records - While modifying records, first we must ask the user which record he intends to modify. Instead of asking the record number to be modified, it would be more meaningful to ask for the name of the person whose record is to be modified. On modifying the record, the existing record gets overwritten by the new record.
• Change flight rates - To do this, first we must ask the user to enter the code for the flight whose flight rates are to be changed. After that, we ask the user to enter new flight rates for that flight.
• Delete records - In deleting records, except for the record to be deleted, rest of the records must first be written to a temporary file, then the original file must be deleted, and the temporary file must be renamed back to original.
• Observe carefully the way the file has been opened, first for reading & writing, and if this fails (the first time you run this program it would certainly fail, because that time the file is not existing), for writing and reading. It is imperative that the file should be opened in binary mode.
• Note that the file is being opened only once and closed only once, which is quite logical.

Header Files Added:

1. stdio.h - For standard Input/Output (I/O) operations.
2. conio.h - For clrscr() and getch() functions.
3. string.h - For string handling.

Understanding of the program: To understand how this program works, we need to be familiar with concept of pointers. A pointer is initiated whenever we open a file. On opening a file, a pointer is set up which points to the first record in the file. To be precise this pointer is present in the structure to which the file pointer returned by fopen() points to. On using the functions fread() or fwrite(), the pointer moves to the beginning of the next record. On closing a file the pointer is deactivated. Note that the pointer movement is of utmost importance since fread() always reads that record where the pointer is currently placed. Similarly, fwrite() always writes the record where the pointer is currently placed.

The rewind() function places the pointer to the beginning of the file, irrespective of where it is present right now.

The fseek() function lets us move the pointer from one record to another. In the program, to move the pointer to the previous record from its current position, I used this function.

fseek(fp, -recsize, SEEK_CUR);

Here, -recsize moves the pointer back by recsize bytes from the current position. SEEK_CUR is a macro defined in stdio.h. Similarly, the following fseek() would place the pointer beyond the last record in the file.

fseek(fp, 0, SEEK_END);

In fact, -recsize or 0 are just the offsets that tell the compiler by how many bytes should the pointer be moved from a particular position. The third argument could be SEEK_END, SEEK_CUR or SEEK_SET. All these act as a reference from which the pointer should be offset. SEEK_END means move the pointer from the end of the file. SEEK_CUR means move the pointer with reference to its current position and SEEK_SET means move the pointer with reference to the beginning of the file.

If we wish to know where the pointer is positioned right now, we can use he function ftell(). It returns this position as a long int wich is an offset from the beginning of the file. The value returned by ftell() can be used in subsequent calls to fseek(). A sample call to ftell() is shown below:

position = ftell(fp);

where position is a long int.

Output

1. Welcome screen

   

2. New record

   i.

   

   ii.

   

3. List records

   

4. Search records

   

5. Modify records

   

6. Change flight rates

   

7. Delete records