INDEX SEQUENTIAL FILE
Following code illustrates the concept of index sequential file:
/***********************************************************************
Program for performing various operations on
Index Sequential File organisation.
************************************************************************/
#include<iostream.h>
#include<iomanip.h>
#include<fstream.h>
#include<string.h>
#include<conio.h>
#include<stdlib.h>
class EMP_CLASS
{
typedef struct EMPLOYEE
{
char name[10];
int emp_id;
int salary;
}Rec;
typedef struct INDEX
{
int emp_id;
int position;
}Ind_Rec;
Rec Records;
Ind_Rec Ind_Records;
public:
EMP_CLASS();
void Create();
void Display();
void Update();
void Delete();
void Append();
void Search();
};
EMP_CLASS::EMP_CLASS()//constructor
{
strcpy(Records.name,"");
}
void EMP_CLASS::Create()
{
int i,j;
char ch='y';
fstream seqfile;
fstream indexfile;
i=0;
indexfile.open("IND.DAT",ios::in|ios::out|ios::binary);
seqfile.open("EMP.DAT",ios::in|ios::out|ios::binary);
do
{
cout<<"\n Enter Name: ";
cin>>Records.name;
cout<<"\n Enter Emp_ID: ";
cin>>Records.emp_id;
cout<<"\n Enter Salary: ";
cin>>Records.salary;
seqfile.write((char*)&Records,sizeof(Records))<<flush;
Ind_Records.emp_id=Records.emp_id;
Ind_Records.position=i;
indexfile.write((char*)&Ind_Records,sizeof(Ind_Records))<<flush;
i++;
cout<<"\nDo you want to add more records?";
cin>>ch;
}while(ch=='y');
seqfile.close();
indexfile.close();
}
void EMP_CLASS::Display()
{
fstream seqfile;
fstream indexfile;
int n,i,j;
seqfile.open("EMP.DAT",ios::in|ios::out|ios::binary);
indexfile.open("IND.DAT",ios::in|ios::out|ios::binary);
indexfile.seekg(0,ios::beg);
seqfile.seekg(0,ios::beg);
cout<<"\n The Contents of file are ..."<<endl;
i=0;
while(indexfile.read((char *)&Ind_Records,sizeof(Ind_Records)))
{
i=Ind_Records.position*sizeof(Rec);//getting pos from index file
seqfile.seekg(i,ios::beg);//seeking record of that pos from seq.file
seqfile.read((char *)&Records,sizeof(Records));//reading record
if(Records.emp_id!=-1)//if rec. is not deleted logically
{ //then display it
cout<<"\nName: "<<Records.name<<flush;
cout<<"\nEmp_ID: "<<Records.emp_id;
cout<<"\nSalary: "<<Records.salary;
cout<<"\n";
}
}
seqfile.close();
indexfile.close();
}
void EMP_CLASS::Update()
{
int pos,id;
char New_name[10];
int New_emp_id;
int New_salary;
cout<<"\n For updation,";
cout<<"\n Enter the Emp_ID for for searching ";
cin>>id;
fstream seqfile;
fstream indexfile;
seqfile.open("EMP.DAT",ios::in|ios::out|ios::binary);
indexfile.open("IND.DAT",ios::in|ios::out|ios::binary);
indexfile.seekg(0,ios::beg);
pos=-1;
//reading index file for getting the index
while(indexfile.read((char *)&Ind_Records,sizeof(Ind_Records)))
{
if(id==Ind_Records.emp_id)//the desired record is found
{
pos=Ind_Records.position;//getting the position
break;
}
}
if(pos==-1)
{
cout<<"\n The record is not present in the file";
return;
}
else
{
cout<<"\n Enter the values for updation...";
cout<<"\n Name: ";cin>>New_name;
cout<<"\n Salary: ";cin>>New_salary;
//calculating the position of record in seq. file using the pos of ind. file
int offset=pos*sizeof(Rec);
seqfile.seekp(offset);//seeking the desired record for modification
strcpy(Records.name,New_name);//can be updated
Records.emp_id=id;//It's unique id,so don't change
Records.salary=New_salary;//can be updated
seqfile.write((char*)&Records,sizeof(Records))<<flush;
cout<<"\n The record is updated!!!";
}
seqfile.close();
indexfile.close();
}
void EMP_CLASS::Delete()
{
int id,pos;
cout<<"\n For deletion,";
cout<<"\n Enter the Emp_ID for for searching ";
cin>>id;
fstream seqfile;
fstream indexfile;
seqfile.open("EMP.DAT",ios::in|ios::out|ios::binary);
indexfile.open("IND.DAT",ios::in|ios::out|ios::binary);
seqfile.seekg(0,ios::beg);
indexfile.seekg(0,ios::beg);
pos=-1;
//reading index file for getting the index
while(indexfile.read((char *)&Ind_Records,sizeof(Ind_Records)))
{
if(id==Ind_Records.emp_id) //desired record is found
{
pos=Ind_Records.position;
Ind_Records.emp_id=-1;
break;
}
}
if(pos==-1)
{
cout<<"\n The record is not present in the file";
return;
}
//calculating the position of record in seq. file using the pos of ind. file
int offset=pos*sizeof(Rec);
seqfile.seekp(offset);//seeking the desired record for deletion
strcpy(Records.name,"");
Records.emp_id=-1; //logical deletion
Records.salary=-1; //logical deletion
seqfile.write((char*)&Records,sizeof(Records))<<flush;//writing deleted status
//From index file also the desired record gets deleted as follows
offset=pos*sizeof(Ind_Rec);//getting position in index file
indexfile.seekp(offset); //seeking that record
Ind_Records.emp_id=-1; //logical deletion of emp_id
Ind_Records.position=pos;//position remain unchanged
indexfile.write((char*)&Ind_Records,sizeof(Ind_Records))<<flush;
seqfile.seekg(0);
indexfile.close();
seqfile.close();
cout<<"\n The record is Deleted!!!";
}
void EMP_CLASS::Append()
{
fstream seqfile;
fstream indexfile;
int pos;
indexfile.open("IND.DAT",ios::in|ios::binary);
indexfile.seekg(0,ios::end);
pos=indexfile.tellg()/sizeof(Ind_Records);
indexfile.close();
indexfile.open("IND.DAT",ios::app|ios::binary);
seqfile.open("EMP.DAT",ios::app|ios::binary);
cout<<"\n Enter the record for appending";
cout<<"\nName: ";cin>>Records.name;
cout<<"\nEmp_ID: ";cin>>Records.emp_id;
cout<<"\nSalary: ";cin>>Records.salary;
seqfile.write((char*)&Records,sizeof(Records));//inserting rec at end in seq. file
Ind_Records.emp_id=Records.emp_id; //inserting rec at end in ind. file
Ind_Records.position=pos; //at calculated pos
indexfile.write((char*)&Ind_Records,sizeof(Ind_Records))<<flush;
seqfile.close();
indexfile.close();
cout<<"\n The record is Appended!!!";
}
void EMP_CLASS::Search()
{
fstream seqfile;
fstream indexfile;
int id,pos,offset;
cout<<"\n Enter the Emp_ID for searching the record ";
cin>>id;
indexfile.open("IND.DAT",ios::in|ios::binary);
pos=-1;
//reading index file to obtain the index of desired record
while(indexfile.read((char *)&Ind_Records,sizeof(Ind_Records)))
{
if(id==Ind_Records.emp_id)//desired record found
{
pos=Ind_Records.position;//seeking the position
break;
}
}
if(pos==-1)
{
cout<<"\n Record is not present in the file";
return;
}
//calculate offset using position obtained from ind. file
offset=pos*sizeof(Records);
seqfile.open("EMP.DAT",ios::in|ios::binary);
//seeking the record from seq. file using calculated offset
seqfile.seekg(offset,ios::beg);//seeking for reading purpose
seqfile.read((char *)&Records,sizeof(Records));
if(Records.emp_id==-1)
{
cout<<"\n Record is not present in the file";
return;
}
else //emp_id=desired record’s id
{
cout<<"\n The Record is present in the file and it is...";
cout<<"\n Name: "<<Records.name;
cout<<"\n Emp_ID: "<<Records.emp_id;
cout<<"\n Salary: "<<Records.salary;
}
seqfile.close();
indexfile.close();
}
void main()
{
EMP_CLASS List;
char ans='y';
int choice,key;
clrscr();
do
{
cout<<"\n Main Menu "<<endl;
cout<<"\n 1.Create";
cout<<"\n 2.Display";
cout<<"\n 3.Update";
cout<<"\n 4.Delete";
cout<<"\n 5.Append";
cout<<"\n 6.Search";
cout<<"\n 7.Exit";
cout<<"\n Enter your choice: ";
cin>>choice;
switch(choice)
{
case 1:List.Create();
break;
case 2:List.Display();
break;
case 3:List.Update();
break;
case 4:List.Delete();
break;
case 5:List.Append();
break;
case 6:List.Search();
break;
case 7:exit(0);
}
cout<<"\n\t Do you want to go back to Main Menu?";
cin>>ans;
}while(ans=='y');
}
Please feel free to ask if you face any problem in understanding the code.
values are not stored in files after the create is done no files will be present there to display. please give the solution.....
ReplyDeletechange the filename in the code and you have to mention the pat of your file and your file should be in .txt fromat
Delete