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need help in lib management project
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this is a project made by me but its issue function is not working well instead of modifying and changing the value of issue to 2 it is adding another book with issue 2 in the file can some one correct it
// **library management** //
// **library members can add,delete,modify and search book** //
// **library members can operate users account** //
// **user can manage his record,issue and return a book** //
// **user can take only 1 book at a time** //
// **library management** //
// **library members can add,delete,modify and search book** //
// **library members can operate users account** //
// **user can manage his record,issue and return a book** //
// **user can take only 1 book at a time** //
C++ Syntax (Toggle Plain Text)
Last edited by Ancient Dragon; Jan 25th, 2009 at 7:40 am. Reason: add code tags
Well, I don't see a function called issue(). I do see a function called issuebook(). Is that the one you are refering to?
While waiting for reply I offer the following in terms of general recommendations.
1) Don't use void as the return type of main(), even if your compiler let's you. It's not standard and it's one more keystroke than typing int.
2) Don't use the return value of eof() as the controlling value of a loop. Sooner or later it is going to create problems, such as looping through a sequence of code one too many times which may cause duplication of the last set of valid input and may overwrite an array, etc.
3) you have declared two mainmenu() functions. Erase the first one at the top of the code as it does nothing.
4) hopefully you indent your code when writing it (if not, do so!) and the indentation was lost when you posted it here because of the way the board works. To prevent that from happening in the future read about using code tags around the code posted to maintain the indentation, etc. Information about using code tags is in the watermark before you start typing into the Message box, and even better, in one of the announcements at the top of this board.
Many people here won't read code if not indented, especially if it's long, because it's just too hard to do comfortably.
4) Try to be more specific when asking questions---what isn't working right about the function? And try to be more specific about the code you post. Hopefully if you ask a specific enough question you can post just the function in question and not the whole program. If additional code is requested by a respondent, then you can post it.
5) Comment your code. It will help you decode it and it will help people reading your code figure out what you are actually trying to do instead of trying to make a guess.
While waiting for reply I offer the following in terms of general recommendations.
1) Don't use void as the return type of main(), even if your compiler let's you. It's not standard and it's one more keystroke than typing int.
2) Don't use the return value of eof() as the controlling value of a loop. Sooner or later it is going to create problems, such as looping through a sequence of code one too many times which may cause duplication of the last set of valid input and may overwrite an array, etc.
3) you have declared two mainmenu() functions. Erase the first one at the top of the code as it does nothing.
4) hopefully you indent your code when writing it (if not, do so!) and the indentation was lost when you posted it here because of the way the board works. To prevent that from happening in the future read about using code tags around the code posted to maintain the indentation, etc. Information about using code tags is in the watermark before you start typing into the Message box, and even better, in one of the announcements at the top of this board.
Many people here won't read code if not indented, especially if it's long, because it's just too hard to do comfortably.
4) Try to be more specific when asking questions---what isn't working right about the function? And try to be more specific about the code you post. Hopefully if you ask a specific enough question you can post just the function in question and not the whole program. If additional code is requested by a respondent, then you can post it.
5) Comment your code. It will help you decode it and it will help people reading your code figure out what you are actually trying to do instead of trying to make a guess.
Klatu Barada Nikto
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I agree with all of Lerner's comments.
I decided your problem looked like fun so I decided to try and get it to compile on my system.
What Compiler are you using?
What is your target Operating System?
(My compiler didn't have support for the BGI graphics so I had to comment it all out -- and fix several other things that relied on it working.)
First major oops is that you keep calling mainmenu() to return to the main menu. That does NOT return to the main menu, it calls a brand new mainmenu that in theory would return to where you called it from, but your mainmenu() as coded will never return.
Every time you make a menu selection and return to the main menu your stack gets a little smaller, eventually (if you ran the program long enough) you would run out and the program will fault.
I'll keep converting and trying to get it to compile / run. But a good specific question would be very helpful. (Something like "When I select ___ from the ___ menu, I expected to see ___ but I see ___ instead. What did I miss?" gives good location and information.) The better the information you give the more likely you are to get a useful answer.
I decided your problem looked like fun so I decided to try and get it to compile on my system.
What Compiler are you using?
What is your target Operating System?
(My compiler didn't have support for the BGI graphics so I had to comment it all out -- and fix several other things that relied on it working.)
First major oops is that you keep calling mainmenu() to return to the main menu. That does NOT return to the main menu, it calls a brand new mainmenu that in theory would return to where you called it from, but your mainmenu() as coded will never return.
Every time you make a menu selection and return to the main menu your stack gets a little smaller, eventually (if you ran the program long enough) you would run out and the program will fault.
I'll keep converting and trying to get it to compile / run. But a good specific question would be very helpful. (Something like "When I select ___ from the ___ menu, I expected to see ___ but I see ___ instead. What did I miss?" gives good location and information.) The better the information you give the more likely you are to get a useful answer.
ok this is actually my 1st c++ prog.This is the issuebook function some how i have corrected the first mistake.
IT takes an user id reads the user file and check if the status( a data member ) is 1 or not if 1 it allow u to issue a book. then the function search book search the books and return its code to bbcode if search is unsuccessful than 0 is returned now after the book is issued the value of issue of book becomes 2 and value of status of user becomes 2.
now the value of issue is showing to be 2 but not that of status of user it is still showing 1.
IT takes an user id reads the user file and check if the status( a data member ) is 1 or not if 1 it allow u to issue a book. then the function search book search the books and return its code to bbcode if search is unsuccessful than 0 is returned now after the book is issued the value of issue of book becomes 2 and value of status of user becomes 2.
now the value of issue is showing to be 2 but not that of status of user it is still showing 1.
C++ Syntax (Toggle Plain Text)
Last edited by Ancient Dragon; Jan 25th, 2009 at 7:39 am. Reason: add code tags
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Did you see the note about code tags?
When posting c++ code, please use c++ code tags
[code=c++]
// Your code here
[/code]
When posting c++ code, please use c++ code tags
[code=c++]
// Your code here
[/code]
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You're not using the same style of seek for both files.
The user file never gets closed.
You're still calling for a new mainmenu().
You didn't answer the Compiler and O/S questions.
c++ Syntax (Toggle Plain Text)
The user file never gets closed.
c++ Syntax (Toggle Plain Text)
You're still calling for a new mainmenu().
You didn't answer the Compiler and O/S questions.
read your code and have some personal suggestions about that:
is it better to have different classes like
??
is it better to have different classes like
class libmembers
{
}class libusers
{
}class book
{
}??
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#
fstream iofile("user.dat",ios::in|ios::out|ios::binary);
#
fstream ifile("lib.dat",ios::in|ios::out|ios::binary);
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#
cout<<"updating users record"<<endl;
#
iofile.seekg(pos);
#
iofile.write((char*)&s1,sizeof(s1));
#
cout<<"updating books record"<<endl;
#
ifile.seekg((rec2-1)*sizeof(b1),ios::beg);
#
ifile.write((char*)&b1,sizeof(book));
But whenever i run the prog the book file is working correctly and the value of issue in book is changing to 2 but it is not writing anything in user record.
i then closed the iofile and opened a new file wofile in output mode only so it just erased all the previos record so if i just use it for 1 user the program is correct but for multiple user it is not.
and murtan i have to pasted some special files named bgifiles in the include folder ( i had taken them from school u can search net ) to enable graphics
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You may have BGI files, but I didn't and so I had to modify the code to get it to compile. I'm running Windows, and as I understand it, BGI is not compatible.
Maybe if I make the questions BIG you'll answer them:
WHAT COMPILER ARE YOU USING?
WHAT OPERATING SYSTEM ARE YOU RUNNING ON?
The point I was making about the seeks, was that one is using ios::beg and the other wasn't, it may be the default, but you made a point of passing it to one and not to the other.
Why use tellg to get position for one file and use a record counter and a mulitply for the other file? Why not use the same method for both files?
(I'm picking at differences between the two because you say one works and the other doesn't.)
If I've been reading through the code correctly, it is designed to loan (issue) one book (that has not already been issued) to the member (that does not already have a book). Is there any sense or record of which member has which book?
Would it ever be desired to issue more than one book to a member? (I know my local library will
)
This application seems like it would lend itself well to a database, might that be an option for ongoing development?
I took your last issue book posted and I'm trying to work with it, but the BGI conversion and the getch() conversions as well as re-writing to not call mainmenu() again are painful.
If you want to modify your program so that mainmenu is a loop, you could use the following as a basis if you like. If you insist on calling mainmenu() from wherever you feel like in your code, I think I'm done trying to take your 'new' code to put in my test application.
My version of your main menu (its not as pretty, but it compiles and runs.)
inputInt is a helper function I wrote, I'm not entirely happy with it, but I was having problems with input stream status so I made a few functions to help me out:
(This code is from another .cpp file that does not have a
Maybe if I make the questions BIG you'll answer them:
WHAT COMPILER ARE YOU USING?
WHAT OPERATING SYSTEM ARE YOU RUNNING ON?
The point I was making about the seeks, was that one is using ios::beg and the other wasn't, it may be the default, but you made a point of passing it to one and not to the other.
Why use tellg to get position for one file and use a record counter and a mulitply for the other file? Why not use the same method for both files?
(I'm picking at differences between the two because you say one works and the other doesn't.)
If I've been reading through the code correctly, it is designed to loan (issue) one book (that has not already been issued) to the member (that does not already have a book). Is there any sense or record of which member has which book?
Would it ever be desired to issue more than one book to a member? (I know my local library will
)This application seems like it would lend itself well to a database, might that be an option for ongoing development?
I took your last issue book posted and I'm trying to work with it, but the BGI conversion and the getch() conversions as well as re-writing to not call mainmenu() again are painful.
If you want to modify your program so that mainmenu is a loop, you could use the following as a basis if you like. If you insist on calling mainmenu() from wherever you feel like in your code, I think I'm done trying to take your 'new' code to put in my test application.
My version of your main menu (its not as pretty, but it compiles and runs.)
c++ Syntax (Toggle Plain Text)
inputInt is a helper function I wrote, I'm not entirely happy with it, but I was having problems with input stream status so I made a few functions to help me out:
c++ Syntax (Toggle Plain Text)
using namespace std; ) well the pos will tell the address of pointer before reading so setting it their and increming in rec++ is just diff method but both fetch same results i used this pos to print the value as i was checking whether it is working right or not so i just printed cout<<pos and then printed cout<<(rec1-1)*sizeof(s1) so both gives same value.
i have just modified the code as opening the iofile in ifstream then close it and open a new file wwfile in output mode so it just erases all the record barring the one using it
but it will work coz atleast i can show the examiner that my program is working
i m using window xp i m not getting what do u mean by compiter but i m using turbo c++ version 3.0
this is the boundation of program user can issue only 1 book at a time.
i have just modified the code as opening the iofile in ifstream then close it and open a new file wwfile in output mode so it just erases all the record barring the one using it
but it will work coz atleast i can show the examiner that my program is working
i m using window xp i m not getting what do u mean by compiter but i m using turbo c++ version 3.0
this is the boundation of program user can issue only 1 book at a time.
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