how to maintain a database????

[anushka]

i just wanted to enter details of some employees and retriving them as required.The following program doesn't have any error.But when i retrive the information,it show the name and designation of the last entry.
Help me to sort this problem.

here's the code

#include<iostream.h>
#include<conio.h>
#include<string.h>
#include<iomanip.h>
#define f 2
class staff
{
int len;
char *name;
public:
int code;
staff()
{}
staff(int c,char *n)
{
len=strlen(n);
code=c;
name=new char[len+1];
strcpy(name,n);
}
void display()
{
cout<<"________staff details____________"<<endl;
cout<<setw(10)<<"code"<<setw(10)<<code<<endl;
cout<<setw(10)<<"name"<<setw(10)<<name<<endl;
}
~staff()
{
delete name;
}
};
class teacher:public staff
{
int len1,len2;
char *sub,*pub;
public:
teacher()
{}
teacher(int c,char *n,char *s,char *p):staff(c,n)
{
len1=strlen(s);
len2=strlen(p);
sub=new char[len1+1];
pub=new char[len2+1];
strcpy(sub,s);
strcpy(pub,p);
}
void show()
{
display();
cout<<setw(10)<<"subject"<<setw(10)<<sub<<endl;
cout<<setw(10)<<"publication"<<setw(10)<<pub<<endl;
cout<<"____________________________"<<endl;
}
~teacher()
{
delete sub;
delete pub;
}
};
class officer:public staff
{
char grade;
public:
officer()
{}
officer(int c,char *n,char g):staff(c,n)
{
grade=g;
}
void show()
{
display();
cout<<setw(10)<<"grades"<<setw(10)<<grade<<endl;
cout<<"_______________________________"<<endl;
}
};
class typist:public staff
{
int speed;
public:
typist()
{}
typist(int c,char *n,int s):staff(c,n)
{
speed=s;
}
void print()
{
display();
cout<<setw(10)<<"speed"<<setw(10)<<speed<<endl;
}
};
class regular:public typist
{
public:
regular()
{}
regular(int c,char *n,int s):typist(c,n,s)
{}
void show()
{
print();
cout<<"_________________________________"<<endl;
}
};
class casual:public typist
{
float daily_wages;
public:
casual()
{}
casual(int c,char *n,int s,float dw):typist(c,n,s)
{
daily_wages=dw;
}
void show()
{
print();
cout<<setw(10)<<"daily wages"<<setw(10)<<daily_wages<<endl;
cout<<"_________________________________"<<endl;
}
};
int main()
{
clrscr();
int d,i=0,h=0,j=0,k=0,sp,dw,e,m,co;
char g,x;
char *s=new char[10];
char *p=new char[10];
char *n=new char[10];
teacher t[f];
officer o[f];
regular r[f];
casual c[f];
do
{
cout<<"wants to make entry/search 1 or 2"<<endl;
cin>>e;
switch(e)
{
case 1:
do
{
cout<<"enter details of employee(code,name)"<<endl;
cin>>co>>n;
cout<<"enter 1 for teacher"<<endl<<"2 for officer"<<endl<<
"3 for regular typist"<<endl<<"4 for casual typist"<<endl;
cin>>d;
switch(d)
{
case 1:
cout<<"enter subject and publication"<<endl;
cin>>s>>p;
t[i]=teacher(co,n,s,p);
i++;
break;
case 2:
cout<<"enter grades"<<endl;
cin>>g;
o[h]=officer(co,n,g);
h++;
break;
case 3:
cout<<"enter speed"<<endl;
cin>>sp;
r[j]=regular(co,n,sp);
j++;
break;
case 4:
cout<<"enter speed and daily wages"<<endl;
cin>>sp>>dw;
c[k]=casual(co,n,sp,dw);
k++;
}
cout<<"wants to enter more y/n";
cin>>x;
clrscr();
}while(x=='y');
break;
case 2:
do
{
cout<<"enter code and designation of employee"<<endl;
cout<<"enter 1 for teacher"<<endl<<"2 for officer"<<endl<<
"3 for regular typist"<<endl<<"4 for casual typist"<<endl;
cin>>co>>d;
switch(d)
{
case 1:
for(m=0;m<i;m++)
{
if(t[m].code==co)
t[m].show();
}
if(m==i)
cout<<"not an employee";
break;
case 2:
for(m=0;m<h;m++)
{
if(t[m].code==co)
t[m].show();
}
if(m==h)
cout<<"not an employee";
break;
case 3:
for(m=0;m<j;m++)
{
if(t[m].code==co)
t[m].show();
}
if(m==j)
cout<<"not an employee";
break;
case 4:
for(m=0;m<k;m++)
{
if(t[m].code==co)
t[m].show();
}
if(m==k)
cout<<"not an employee";
}
cout<<"wants to search more y/n";
cin>>x;
clrscr();
}while(x=='y');
}
cout<<"wants to work more y/n";
cin>>x;
clrscr();
}while(x=='y');
delete s;
delete p;
delete n;
getch();
return 0;
}

sorry for the inconvenience

[m4ster r0shi]

Edit your original post and use code tags -> [code] your code here [/code]

[m4ster r0shi]

Ok. There are more than one errors here :P

First, take a look at this:

cout<<"enter subject and publication"<<endl;
cin>>s>>p;
t[i]=teacher(co,n,s,p);
i++;

This line -> t[i]=teacher(co,n,s,p); creates a nameless, temporary teacher object (I'll call it temp), then assigns it to t[i], then destroys that temporary teacher object. You haven't defined an assignment operator for your teacher class, so the default one is used. This means that the following assignments take place:

t[i].len=temp.len; //<- ok
t[i].name=temp.name; //<- problem!
t[i].code=temp.code; //<- ok
t[i].len1=temp.len1; //<- ok
t[i].len2=temp.len2; //<- ok
t[i].sub=temp.sub; //<- problem!
t[i].pub=temp.pub; //<- problem! 

Pointer copying creates a problem here because these pointers are deleted right away with the destruction of temp. A solution for this would be to define your own assignment operator that actually copies the strings. Oh, and this is applied to all of your classes, not just the teacher.

Second, your program only prints one record because that's what you tell it to (assuming that code is unique for each record)

for(m=0;m<i;m++)
{
    if(t[m].code==co)
        t[m].show();
}
if(m==i) cout<<"not an employee";

Third, this here is not good design for object containers:

#define f 2

//...

teacher t[f];
officer o[f];
regular r[f];
casual c[f];

What if the user enters more than 2 teachers? Your program will most probably crash (If you tried it and it didn't crash then you were just lucky). Try the STL containers instead (vector, list, deque, etc...):

http://cplusplus.com/reference/stl/

EDIT: It would also save you a lot of typing if you used an std::string instead of char pointers to implement your strings:

http://cplusplus.com/reference/string/string/

[anushka]

thanks for the suggestion!
>Second, your program only prints one record because that's what you tell it to (assuming that code is unique for each record)

but i want to print only the required one.
i am a beginner i am not able to define my one assignment operator
so please help me out this

[m4ster r0shi]

anushka wrote:

but i want to print only the required one.

Oh, ok. Then, I guess I didn't understand what the problem with that was...

anushka wrote:

i am a beginner i am not able to define my one assignment operator
so please help me out this

Take a look at these here:

http://www.learncpp.com/cpp-tutorial/911-the-copy-constructor-and-overloading-the-assignment-operator/

http://www.learncpp.com/cpp-tutorial/912-shallow-vs-deep-copying/

Also, note that when you overload either the assignment operator or the copy constructor it's good to overload the other one too.