Question 1
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#include <iostream>
#include <fstream>
using namespace std;

int main() {

  string filename;
  float x, sum=0;
  int count=0;

  cout << "Enter input filename: ";
  cin >> filename;

  const char* fs = filename.c_str();

  ifstream MyReadFile(fs);

  while (MyReadFile >> x) {
        count++;
        sum = sum + x;
  }

  // Close the file
  MyReadFile.close();


  cout << "sum = " << sum << endl;
  cout << "count = " << count << endl;
  cout << "average = " << sum/count << endl;
  return 0;
}


Question 2
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#include <iostream>
#include <fstream>
using namespace std;

int main() {

  string ifile, ofile;
  int count=0, nums[100], i;

  cout << "Input filename: ";
  cin >> ifile;

  cout << "Output filename: ";
  cin >> ofile;

  const char* ifs = ifile.c_str();
  const char* ofs = ofile.c_str();

  ifstream MyReadFile(ifs);
  ofstream MyWriteFile(ofs);

  while (MyReadFile >> nums[count])
        count++;


  for(i=count-1;i>=0;i--)
    MyWriteFile << nums[i] << endl;


  // Close the file
  MyReadFile.close();
  MyWriteFile.close();

  cout << "Program completed successfully" << endl;

  return 0;
}

Question 3
---------------------------------------------------------
#include <iostream>
#include <fstream>
using namespace std;

int main() {

  int count=0, nums[100], i, key;

  ifstream MyReadFile("q03.txt");

  while (MyReadFile >> nums[count])
        count++;

  while(true){
    cout << "Enter the number = ";
    cin >> key;

    i = 0;
    while(key != nums[i] && i < count)
      i++;

    if(i==count)
      cout << "Not found" << endl;
    else
      cout << "It is at position " << i << endl;
  }
  // Close the file
  MyReadFile.close();

  cout << "Program completed successfully" << endl;

  return 0;
}

Question 5(a)
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int main(){
        char x;
        ofstream ofile("text5a.txt");
        ifstream ifile("text5.txt");

        while(ifile >> x){
                ofile << (char)(x-1);
        }
        return 0;
}

Question 5(b)
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int main(){
        char x,y;
        ofstream ofile("text5b.txt");
        ifstream ifile("text5.txt");
        ifile>>x;
        ifile>>y;
        while(!ifile.eof()){
                ofile << y;
                ofile << x;

                ifile>>x;
                ifile>>y;
        }
        if(x!=EOF)
                ofile << x;
        ifile.close();
        ofile.close();
        return 0;
}


Question 6
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int main(){
        	string word, sub="era";
        	bool found;
        	int j,k;
        	ofstream ofile("q6_out.txt");
        	ifstream ifile("q6_in.txt");
        	int i=0;
        	while(ifile >> word){
                	j=0;
                	found = true;
                	while(j<=(word.length()-3)&&found){
                        		k=0;
                        		found = true;
                        		while(k<3&&found){
                                		if(word[j+k]!=sub[k])
                                        			found=false;
                                		k++;
                        		}
                        	if(found){
                                		ofile << word << endl;
                                		found = false;
                        		}
                        		else
                                		found=true;
                        		j++;
                }
        }
        ofile.close();
        ifile.close();
        return 0;			
}

Question 7
------------------------------------------------------------------------------------
#include <iostream>
#include <fstream>
using namespace std;
string names[100];
string tel[100];
int readFile(){
        int i=0;
        ifstream f("q7.txt");
        do{
                f>>names[i];
                f>>tel[i];
                i++;
        }while(!f.eof());
        f.close();
        return i-1;
}
void writeFile(int total){

        int i;
        ofstream f("q7.txt");
        for(i=0;i<total;i++){
                f<<names[i];
                f<<"\t";
                f<<tel[i];
                f<<endl;
        }
}
void listRecord(int total){

        int i;
        for(i=0;i<total;i++){
                cout << names[i] << "\t" << tel[i] << endl;
        }

}
int insertRecord(int total){
        if(total==99){
                cout << "The storage is full!" << endl;
                return 0;
        }
        else{
                cout << "Inserting record..." << endl;
                cout << "Name: ";
                cin >> names[total];
                cout << "Tel no: ";
                cin >> tel[total];
                return 1;
        }
}
int deleteRecord(int total){
        int i,j;
        string n;
        if(total==0){
                cout << "The storage is empty" << endl;
                return 0;
        }
        else{
                cout << "Deleting record..." << endl;
                cout << "Name: ";
                cin >> n;
                i=0;
                while(names[i]!=n&&i<total)
                        i++;
                if(i==total){
                        cout << "Name Not Found" << endl;
                        return 0;
                }
                else{
                        for(j=i;j<total-1;j++){
                                names[j]=names[j+1];
                                tel[j]=tel[j+1];
                        }
                        return 1;
                }
        }

}
void updateRecord(int total){
        string n, t;
        int i;
        cout << "Updating record..." << endl;
        cout << "Name: ";
        cin >> n;
        i=0;
        while(names[i]!=n&&i<total)
                i++;
        if(i==total){
                cout << "Name Not Found" << endl;
        }
        else{
                cout << "Old tel no: " << tel[i] << endl;
                cout << "New tel no: ";
                cin >> t;
                tel[i]=t;
        }
}

int getMenuChoice(){
        int choice;
        cout << "Telephone Enquiry System\n1) List Records\n2) Insert Record\n3) Delete Record\n4) Updat$

        do{
                cout << "Choice :";
                cin >> choice;
        }while(choice<0||choice>5);

        return choice;
}
int main(){

        int total, choice;
        total=readFile();

        do{
                choice=getMenuChoice();

                if(choice==1)
                        listRecord(total);
                else if(choice==2)
                        total=total+insertRecord(total);
                else if(choice==3)
                        total=total-deleteRecord(total);
                else if(choice==4)
                        updateRecord(total);
                else
                        writeFile(total);

        }while(choice!=5);

        return 0;

}