C++ hw help

Last Edited By Krjb Donovan
Last Updated: Mar 12, 2014 02:46 PM GMT

Question

I have to do a program that converts telephone numbers into letters. If the user enters more than seven letters, then process only the first seven letters. My program compiles and works somewhat properly but it is processing more than 7 numbers. I tried to use a counter but I cannot figure out how to stop it from processing numbers past 7. My code is below. Please help me.

  1. include <iostream>
  2. include <stdlib.h>

using namespace std;

int main() { char letter; //Line 1

cout << "Program to convert " << "letters to their corresponding " << "telephone digits." << endl; //Line 2

 do {

cout << "To stop the program enter #." << endl; //Line 3

cout << "Enter letters used for a phone number and press Enter:"; //Line 4 cin >> letter; //Line 5

// WE USE THIS TO ITERATE THROUGH THE CODE int counter = 0; while (letter != '\n') { if (counter == 3 && counter != 0) cout << "-"; if ( letter == '#') break; if ((letter >= 'A' && letter <= 'Z') //Line 10 || (letter >= 'a' && letter <= 'z' ) ) switch (letter) //Line 11 { case 'A': case 'B': case 'C': case 'a': case 'b': case 'c': cout << "2"; //Line 12 break;

           					//Line 13

case 'D': case 'E': case 'F': case 'd': case 'e': case 'f': cout << "3"; //Line 14 break;

           					//Line 15

case 'G': case 'H': case 'I': case 'g': case 'h': case 'i': cout << "4"; //Line 16 break;

           						//Line 17

case 'J': case 'K': case 'L': case 'j': case 'k': case 'l': cout << "5"; //Line 18 break;

           						//Line 19

case 'M': case 'N': case 'O': case 'm': case 'n': case 'o': cout << "6"; //Line 20 break;

           						//Line 21

case 'P': case 'Q': case 'R': case 'S': case 'p': case 'q': case 'r': case 's': cout << "7"; //Line 22 break;

           						//Line 23

case 'T': case 'U': case 'V': case 't': case 'u': case 'v': cout << "8"; //Line 24 break;

           							//Line 25

case 'W': case 'X': case 'Y': case 'Z': case 'w': case 'x': case 'y': case 'z': cout << "9"; //Line 26

case ' ': case '\t': break; } // end of switch statement else //Line 27 cout << "Invalid input." << endl; //Line 28

cin >> letter; //Line 32 counter ++; // INCREMENT OUR COUNTER } //end of while loop for letters cout << endl;

  } while (letter != '#');//no more input
  system ("Pause");
  return 0;

}


Answer

Change the while statement from

      while (letter != '\n') to
      while( counter < 7 )

and you should be ok.

Note:

  1. include <stdlib.h>

There is no such header in ISO C++. Use #include <cstdlib> instead.

system("pause") represents a vulnerability (an unsafe programming practice) which can be exploited by an attacker. A malicious attacker could replace the "pause" program on the machine with a program that does some kind of damage, and use it to cause trouble. Spoofing a legitimate and harmless program is a common practice among malware.

In addition, it also has the drawback that the argument string is not portable across different implementations. Your code may work on windows, but may do something completely different (or not work at all) on unix.

A portable and less risky way is to write:

 std::cin >> std::ws ; // throw away white spaces remaining in the input buffer
 std::cin.get() ; // wait for the user to enter a new line

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