Question about c program

I am a junior student in programming. I need to write a c program for a library, which shows different book sections.

It must prompt the user to enter a section number from 1-5. Then the program must show a grid 10 columns by 10 rows, each grid entry showing a book. The program must prompt the user to enter a row, and then a column. It must tell the user if that space is already taken by a book, if it is not, one can store a book there and enter its details.

The program must also have an option , which shows the user the different sections , and shows the taken spaces by books by an 'O', and the free spaces by an '-'. The details of the books and grid sections must be entered in a file, so that the user can see which spaces are taken in the different sections.

Can someone help me please ? I will give best answer !

I am finding it difficult to create the grid and how can I store the details in the different spaces of he grid please ?


This is the main menu of the program :

Code:

---

int menu()
{
int choice = 0;

do
{
printf("1. Show Section \n"); //then user has to specify which section, and grid of section is then shown, showing taken(O) and vacant spaces(-).
printf("2. Enter new book entry\n"); //user has to specify which section , then section is shown, showing taken spaces and vacant spaces. User has to enter section , then a row and column. If space is vacant, user mus enter details of new book. Else if there is already a book , an error must be shown.

printf("3. Quit\n");

printf("\nEnter choice: ");
scanf("%d", &choice);
}
while ((choice 3));

return choice;
}


---

This is the structured information that each space must hold :

Code:

---

typedef struct Book
{

char name[50];

char author[50];
char ISBN[10];

} Book;


---

How can I create the grid and relate this structure with every space in each section in the grid? Can someone help me pls ?

Hello,

Why wait for the user to enter a row and a column to tell him if that spot is empty or not ? You said that it must have an option of displaying "O" or "-" ..

I don't think this should be an option, I think it should be the default thing to do: It's an important information you know the user will ask for, so why wait for him to do so ?

So basically, you want to display a Section[X][Y] and print "O" and "-" in each element of that.. ?

As a side note, I think you should check again your while loop and think about adding a condition for the section number among other things. (between 1 & 5).

So.. a library consists of 5 sections, and each section is a grid of 10x10 books?

Code:

---

typedef struct Book
{
  char name[50];

  char author[50];
  char ISBN[10];

} Book;

---

So there's a Book. What does each entry in a grid have? A book. What does each section have? 10x10 books. So you could do:

Code:

---

Book library[5][10][10];

---

Given a section s, row r and column c you could access e.g. Author like:

Code:

---

library[s][r][c].author;

---

I don't really care for this way though. Everything is expressed in varying dimensions of "Book". So library[x] gives a grid which is type Book[10][10], library[x][y] gives a row, which is type Book[10]. Yeugh. Probably the way most people would do it, but I'd personally put everything in its own struct.

Code:

---

typedef struct GridEntry
{
        Book book;
        char taken;
} GridEntry;

typedef struct Section
{
        GridEntry grid[10][10];
} Section;

---

Then your library would be

Code:

---

Section library[5];

---

Accessing stuff would look more horrible, but the types are straightforward.

Code:

---

// author access
library[s].grid[r][c].book.author;

---

Either way, to print a section you need to iterate through every Book.

Code:

---

void DisplaySection(Section section)
{
        int r,c;
        for (r = 0; r < 10; r++)
        {
                printf("\n"); // each row on a new line
                for (c = 0; c < 10; c++)
                {
                        printf("%c ", section.grid[r][c].taken);
                }
        }
}

---

Or if you use a multidimensional array of Book and decide author[0] == 0 means space is free:

Code:

---

void DisplaySection(Book section[10][10])
        int r,c;
        for (r = 0; r < 10; r++)
        {
                printf("\n"); // each row on a new line
                for (c = 0; c < 10; c++)
                {
                        printf("%c ", (section.[r][c].book.author[0] == 0 ? '-' : 'O');
                }
        }
}

---

Some random thoughts:
If the sections are numbered 1-5, are the rows/columns numbered 1-10? Don't forget C arrays start at 0, so you need to adjust user input and program output. Section 1 is library[0].
If you expect most spaces to be empty, you might want to consider dynamically allocating space for each Book and storing a pointer in the struct. Save a bit of memory and make it more scalable.
Your menu display function should either return choice, or have a loop. Not both. I prefer to return the choice and have a loop in main().

Code:

---

do
        {
                choice = menu();
                switch(choice)
                          ...blahblahblah
        }  while (choice != 3);

---

Is there no option to display the information for a book at a particular section, row and column?
Writing a human readable file is easy -- but if you need to read the same file back in it could a bit of a pain -- probably not difficult but I don't think you'd be able to reuse many of your interactive-input functions.

Just a note about the title of your post. You're posting in a forum dedicated to asking questions about C programs. So "Question about c program" is not particularly informative. "Program for library of books" is better.

Thanks for your replies , but I am still a bit confused. Is there a way on how to do this without 3-D arrays ?

My way only had 2-D arrays :)

What do you have against multidimensional arrays? It seems to me to be a natural way to represent this.

You could do it with an array of 100 Books for each grid instead, but you'd have to map the 0-99 onto row and column numbers and back again, which seems to be more painful to me.

Code:

---

typedef struct Section
{
    Books grid[100];
} Section;

---

Or you could just store the sections, rows and columns that have things in them. So have

Code:

---

typedef struct Slot
{
    int section;
    int row;
    int column;
    Book *book;
    Slot *next;
} Slot;

Slot *library;

int SlotTaken(Slot *lib, int s, int r, int c)
{
    // go through the linked list looking for elements that match 
}

void AddBook(Slot *lib, int s, int r, int cm Book *book)
{
  // go to the end of the linked list
  // malloc a new Slot
  // store arguments
}

---

Problem with doing it that way is you'd have to call SlotTaken() a LOT. Like for every print of 'O' or '-' you'd have to call it. If it's a long list that'd be pretty inefficient. You could make it not so bad by having an array of Slot linked lists, instead of just having 1 list. I don't think this'll be easier than multidimensional arrays!

Can you please provide me with the final working code for this program that does the required work ?

I'd rather not -- this is sounding like a homework or an assignment - we're not here to do your work for you!

You should try to do it, then post what you've done and point out where you're stuck.

Quote:

---

Originally Posted by TexasKid

Can you please provide me with the final working code for this program that does the required work ?

---

No one here is going to do your work for you. Obviously you missed this, at the top of the forum.

I am also including some functions that I created :

Code:

---

int showSpace()
{
int section=0;

do
{
printf("Enter Section [1-5]: ");
scanf("%d", &section);


}       
while ((section < 1 ) && (section > 5));

return section;
}

void showGrid(int section)
{
printf(" Section %d \n",section);
}


---

How can I create the grid and relate the book structure with every space in each section in the grid? This is where I am getting really stuck.

So I think I am nearly finished , but the program still has some errors. Can you please help me identify these errors and help me writing the main function ? Throughout the program I am also giving some comments to help explain what is happening.

Code:

---

#include <stdio.h>
#include <string.h>

typedef struct Book {
  char name[50];
  char author[50];
  char ISBN[10];

} Book;

typedef struct Slot {
  Book theBook;
  char isFree;
} Slot;

typedef Slot Section[10][10];  // a section is a grid of 10 rows by 10 columns
typedef Section Library[5];    // a library contains 5 sections

// a book contains name, author, isbn
// a slot contains a book and a flag to say whether the slot is free or taken
// a section is a grid of 10 x 10 slots
// a library contains 5 sections
Library myLibrary;

int menu()
{
  int choice = 0;

  do {
    printf("1. Show Section \n");
    printf("2. Enter new book entry\n");
    printf("3. Quit\n");
    printf("\nEnter choice: ");
    scanf("%d", &choice);
  }
  while ((choice != 3));

  return choice;
}




int showSpace()
{
  int section = 0;

  do {
    printf("Enter Section [1-5]: ");
    scanf("%d", &section);
  }
  while ((section < 1) || (section > 5));

  return section;
}

void showGrid(int section)
{
  int i = 0;
  int k = 0;

  printf("\nBooks in section %d", section);

  for (i = 0; i < 10; i++)      // go through each row
  {
    for (k = 0; k < 10; k++)    // for each row, go through each column
    {
      printf("\n\nSection %d, Row %d, Column %d\n", section, i + 1, k + 1);

      if (myLibrary[section - 1][i][k].isFree == '-') {
        printf("No book at this location");
      } else {
        printf("Author: %s\nTitle: %s\nISBN: %s\n",
                  myLibrary[section-1][i][k].theBook.author,
                  myLibrary[section-1][i][k].theBook.name,
                  myLibrary[section-1][i][k].theBook.ISBN);
      }
    }
  }
}

void DeleteAll()
{
// mark the library as being empty by setting all books to being free
  int s = 0;
  int r = 0;
  int c = 0;

  for (s = 0; s < 5; s++)      // each section
    for (r = 0; r < 10; r++)    // each row in each section
      for (c = 0; c < 10; c++)  // each column in each row
      {
// set it to available
        myLibrary[s][r][c].isFree = '-';
      }
}

int main()
{
// delete all books in the library
  DeleteAll();

  Book myBook;
  strcpy(myBook.author, "some author");
  strcpy(myBook.name, "some name");
  strcpy(myBook.ISBN, "123456789");

// add a book to the library.
// remember C arrays start at 0.
// add a book to section 1, row 2, column 3
  myLibrary[0][1][2].theBook = myBook;
  myLibrary[0][1][2].isFree = 'O';

// show the books in section 1
  showGrid(1);
}

---

Try using "paste as text" when you paste your code, then perhaps it will look like this (syntax coloured, monospaced, and indented) whereas yours is none of these things.

Code:

---

int main ( ) {
    printf("Hello world\n");
    return 0;
}

---

Dude, layoff the post resurrection shotgun!

Soma

The thing is , I don't know how I can relate the structure for the book [of name, author etc] with each space in the grid. Moreover , the grid spaces are not showing (O and -). Can someone help me please?

I don't know what you want.

Code:

---

$ gcc foo.c
$ ./a.out

Books in section 1

Section 1, Row 1, Column 1
No book at this location

Section 1, Row 1, Column 2
No book at this location

Section 1, Row 1, Column 3
No book at this location

Section 1, Row 1, Column 4
No book at this location

Section 1, Row 1, Column 5
No book at this location

Section 1, Row 1, Column 6
No book at this location

Section 1, Row 1, Column 7
No book at this location

Section 1, Row 1, Column 8
No book at this location

Section 1, Row 1, Column 9
No book at this location

Section 1, Row 1, Column 10
No book at this location

Section 1, Row 2, Column 1
No book at this location

Section 1, Row 2, Column 2
No book at this location

Section 1, Row 2, Column 3
Author: some author
Title: some name
ISBN: 123456789

/// A lot more "No book...." prints snipped

---

As written, it seems to do what you posted.

But I need this data to be represented in a grid of rows and columns. Vacant spaces should be marked as '-' , while taken spaces should be 'O'. Program must prompt user to enter row and column , and check whether space is vacant , if it is vacant , the user can enter new entry. I want it to look something like this :

Section 1
1 2 3 4 5 6 7 8 9 10
1 - - - - - - - - - -
2 - - - - - - - - - -
3 - - O - - - O - - -
4 - - - - - - - - - -
5 - - - - - - - - - -
6 - - - - - O - - - -
7 - - - - - - - - - -
8 - - - - - - - - - -
9 - - - - - - - - - -
10- - - - - - - - - -

Now this has to be repeated for each 5 sections.

So change your print function - it's not that hard if you've got this far.

Indeed! This is simple compared to the stuff you already did.

You already have the loops right:

Code:

---

for (i = 0; i < 10; i++)      // go through each row
  {
    for (k = 0; k < 10; k++)    // for each row, go through each column
    {

---

So in here you just want to print the char isFree. So don't use %s, use %c for a char.

That'll print the chars in a long string. Getting it into a grid is easy - just print a newline in the outer loop. Then mess with the spacing until you're happy.

haha you just pin-pointed my problem. I dont' know where I need to print the isFree char :p

How can I go about relating each entry in the array to an '-' or 'O' in the grid , so that each '-' or 'O' represents a record ? How can the grid can then be printed ?