very noob c++ question

[KAMAZON]

Hello, I am doing a simple program out of my text book (it's not required by the school but I want to learn it) and whenever I input a inch value on the compiled program, it gives me some long ass scientific number. Here is the code. I am using Visual Studio C++ 6


int main()
{
//declaring data types

int feet;
int inches;
int totalInches;
double centimeters;

// output and input for inches
cout << "Enter two integers, one for feet and "
<< "one for inches: ";

cin >> feet, inches;
cout << endl;
cout << "The numbers you entered are " << feet
<< " for feet and " << inches
<< " for inches." << endl;

// calculating inches
totalInches = INCHES_PER_FOOT * feet + inches;


cout << "The total number of inches = "
<< totalInches << endl;

// calculating centimeters
centimeters = CENTIMETERS_PER_INCH * totalInches;

cout << "The total number of centimteres = "
<< centimeters << endl;
return 0;
}


Here is the output. Do note I enter 1 1 for the inputs:

Enter two integers, one for feet and one for inches: 1 1

The numbers you entered are 1 for feet and -858993460 for inches.
The total number of inches = -858993448
The total number of centimteres = -2.18184e+009
Press any key to continue

I also get this warning when I compile it:
d:\program files\microsoft visual studio\myprojects\test2\test2.cpp(28) : warning C4700: local variable 'inches' used without having been initialized


Thank you!

 

[KAMAZON]

Well I don't know why what I did worked but I re-wrote it and it works now. Here is what I am using now:

// test2.cpp : Defines the entry point for the console application.
//

#include "iostream"
using namespace std;


int main()
{
//declaring data types

int feet;
int inches;
int totalInches;
double centimeters;


const double CENTIMETERS_PER_INCH = 2.54;
const double INCHES_PER_FOOT = 12;

// output and input for feet
cout << "Enter 1 integer for feet: ";
cin >> feet;
cout << "You have entered " << feet << " feet." << endl;

// output and input for inches
cout << "Enter 1 integer for inches: ";
cin >> inches;
cout << "You have entered " << inches << " inches." << endl;

cout << "The numbers you entered are " << feet
<< " for feet and " << inches
<< " for inches." << endl;

// calculating total inches
totalInches = INCHES_PER_FOOT * feet + inches;

cout << "The total number of inches = "
<< totalInches << endl;


// calculating centimeters
centimeters = CENTIMETERS_PER_INCH * totalInches;


cout << "The total number of centimteres = "
<< centimeters << endl;

return 0;
}

 

[sciencewhiz]

In the first program, you were not using cin correctly for multiple variables, thus nothing was put into inches, so it only had random garbage. The warning that you got tells you this.

See the following page for an example of using cin with multiple variables: http://www.cplusplus.com/doc/tutorial/basic_io.html

 

[KAMAZON]

Sir, I don't care what anyone says about you. You are a gentleman and a scholar, thank you very much!

 

[DanceMan]

Originally posted by: KAMAZON
Sir, I don't care what anyone says about you. You are a gentleman and a scholar, thank you very much!

This made me think of something, that I had to google to see if I remembered correctly, and I did...

Let's just say that he initialized inches = 0. Then the warning would not have been generated. So, what really happened? In C++ (and C) there's the comma operator, and although it was an improper use of the cin, the comma operator was the real culprit here.

I had to check this, mainly because I've been doing all Java programming lately, and I had to see if it was still alive and kicking in Java. It is, but only for FOR loops.

 

[sao123]

Originally posted by: KAMAZON
Hello, I am doing a simple program out of my text book (it's not required by the school but I want to learn it) and whenever I input a inch value on the compiled program, it gives me some long ass scientific number. Here is the code. I am using Visual Studio C++ 6


int main()
{
//declaring data types

int feet;
int inches;
int totalInches;
double centimeters;

// output and input for inches
cout << "Enter two integers, one for feet and "
<< "one for inches: ";

cin >> feet, inches; \\You cant do this...
cin >> feet >> inches; \\Proper coding of this line...
cout << endl;
cout << "The numbers you entered are " << feet
<< " for feet and " << inches
<< " for inches." << endl;

// calculating inches
totalInches = INCHES_PER_FOOT * feet + inches;


cout << "The total number of inches = "
<< totalInches << endl;

// calculating centimeters
centimeters = CENTIMETERS_PER_INCH * totalInches;

cout << "The total number of centimteres = "
<< centimeters << endl;
return 0;
}


Here is the output. Do note I enter 1 1 for the inputs:

Enter two integers, one for feet and one for inches: 1 1

The numbers you entered are 1 for feet and -858993460 for inches.
The total number of inches = -858993448
The total number of centimteres = -2.18184e+009
Press any key to continue

I also get this warning when I compile it:
d:\program files\microsoft visual studio\myprojects\test2\test2.cpp(28) : warning C4700: local variable 'inches' used without having been initialized


Thank you!