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Efficient File Reading and Data Processing in C++

This guide covers techniques for efficiently reading data from a file in C++ using iostream and fstream libraries. It includes examples illustrating how to read numbers until a sentinel value, process a file with known and unknown sizes, and handle end-of-file situations properly. Learn to implement robust data processing methods and examples for reading, including managing various data types. Ideal for developers seeking to enhance their file I/O skills in C++ programming.

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Efficient File Reading and Data Processing in C++

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  1. More About File Reading

  2. Prompts: Not Needed input.dat 3 -1 34 56 3 14 12 6 124 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file do { cout << “What is your next number? ”; } while (fin >> num);

  3. Reading the Entire File input.dat 3 11 34 56 3 14 12 6 124 -1 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file fin >> num; while (num != -1) { process_data(num); fin >> num; }

  4. Reading the Entire File input.dat 3 11 34 56 3 14 12 6 124 -1 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file fin >> num; while (num != -1) { process_data(num); fin >> num; }

  5. Reading the Entire File input.dat 3 11 34 56 3 14 12 6 124 -1 marks end of data #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file fin >> num; while (num != -1) { process_data(num); fin >> num; }

  6. Reading the Entire File input.dat 3 -1 34 56 3 14 12 6 124 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file // SIZE is size of dataset – known a priori for (inti = 0; i < SIZE; i++) { fin >> num; process_data(num); }

  7. Reading the Entire File input.dat 3 -1 34 56 3 14 12 6 124 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file // size of dataset unknown! while (fin >> num) // returns false when last { // data element read process_data(num); }

  8. Reading the Entire File input.dat 3 -1 34 56 3 14 12 6 124 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file while (fin >> num) { fin >> num; process_data(num); }

  9. Reading the Entire File input.dat 3 -1 34 56 3 14 12 6 124 #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file while (fin >> num) { fin >> num; //skips every other datum process_data(num); }

  10. Reading the Entire File input.dat 124663 Price 124645 Hurson 124687 Buechler 124752 Davis #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file while (fin >> num) // gets integer data { fin >> name; // gets name data process_data(num, name); }

  11. Reading the Entire File input.dat 3 -1 34 56 3 14 12 6 124 Note: eof becomes trueonly after trying to read past the last datum #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file fin >> num; // necessary for case of // empty file while (!fin.eof()) { process_data(num); fin >> num; }

  12. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  13. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  14. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  15. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  16. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  17. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  18. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  19. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  20. Example #include <iostream> #include <fstream> using namespace std; int main() { ifstream in; ofstream out;     float next_value; in.open(“input.dat”); out.open(“output.dat”);     while (in>>next_value)      out<<next_value*next_value<<" "; in.close(); out.close();     return 0; }

  21. End of Session

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