C++ noob question - Dev Hardware

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June 24th, 2006, 03:00 PM

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C++ noob question

I recently got into learning C++(by recently, I mean like ten, mabey fifteen minutes ago), I got a compiler, all works well, and I built the typical programmers first program, the hello world bit.

Code:

// my first program in C++

#include <iostream>
using namespace std;

int main ()
{
  cout << "Hello World!";
  cout << "I'm a C++ program";
  return 0;
}

and I compiled it. But, when I run it, it opens, some text flashes up on the screen(I dont know what the text is because it happens within a milisecound), and then it closes, Is this correct? Or have I done something wrong with the above code?

EDIT: it seems that none of the example scripts that a tutorial is giving will run, is it my compiler? i am using one from http://www.bloodshed.net/, is there another one i should use?

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June 24th, 2006, 07:24 PM

MisterEd

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Sound normal. It is probably opening a DOS window, displaying the text, and then closing the window. Open a Commmand Prompt (found in the Start -> Accessories) and run it from there. To run it in Windows and keep the DOS window open you need a cin or something similar at the end to stop the program from exiting until you are ready.

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June 24th, 2006, 09:08 PM

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Quote:

Originally Posted by MisterEd

o.o' you just blew my mind through the back of my skull with that remark, cin? what is that?

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June 24th, 2006, 09:17 PM

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Google "iostream" and read "Thinking in C++ Volume 1" from Bruce Eckel's site. (Its free.)

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June 25th, 2006, 09:16 PM

omrsafetyo

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MisterEd is right.. and kinda unhelpful.

Simplest answer ever:

before the end of your program, include the following code:

Code:

SYSTEM("PAUSE");

Since its running in the CMD window, once the code executes, the command window finishes and closes. putting the PAUSE at the end will cause the CMD window to wait for further user input before closing.. e.g., press any key to continue..

cin by the way is used to read input into a variable. e.g.

Code:

cout << "What's your name";
cin >> name;
cout << "Nice to meet you " << name  << endl;

this would prompt a user for their name, and then when they typed it and pressed enter (cin reads until an end line) it stores the input in a memory address, which is accessed through the variable "name". The 3rd line would then output "Nice to meet you John" - or whatever the name was, followed by an endline i.o.w. a carriage return.

Comments on this post

PunkRocKEVin agrees!

Trader Rating: 1 · #6

June 26th, 2006, 01:35 AM

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Trader Rating: 0 · #7

June 26th, 2006, 02:33 AM

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Quote:

Originally Posted by omrsafetyo

MisterEd is right.. and kinda unhelpful.

Simplest answer ever:

before the end of your program, include the following code:

Code:

SYSTEM("PAUSE");

My code is now this,

Code:

// my first program in C++

#include <iostream>
using namespace std;

int main ()
{
  cout << "Hello World!";
  return 0;
  SYSTEM("PAUSE");
}

and when i try to compile it, it highlights the system part, and gives these three errors

Code:

 C:\Documents and Settings\Bowkid\My Documents\codersanonymous\c++\firstprog.cpp In function `int main()':

Code:

10 C:\Documents and Settings\Bowkid\My Documents\codersanonymous\c++\firstprog.cpp `SYSTEM' undeclared (first use this function)

Code:

  (Each undeclared identifier is reported only once for each function it appears in.)

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June 26th, 2006, 02:54 AM

Itsacon

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That's because SYSTEM() is not an official C function.

try cin.get(), or getch(). Same effect, not compatibility issues.

Last edited by Itsacon : June 26th, 2006 at 02:57 AM.

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June 26th, 2006, 03:27 AM

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could you give an example of one of them?

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June 26th, 2006, 03:52 AM

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Quote:

// my first program in C++

#include <iostream>
#include <stdlib>
using namespace std;

int main ()
{
cout << "Hello World!";
system("PAUSE");
return 0;
}

You need to add #incluce <stdlib> as above and try system with lower case and insert it before return statement.

also you can do following:

Quote:

// my first program in C++

#include <iostream>
using namespace std;

int main ()
{
char *enter;
cout << "Hello World!\n";
cout << "I'm a C++ program\n";
cout << "press enter";
cin >> enter
return 0;
}

Comments on this post

Itsacon agrees: Something like that yes. :-)

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June 26th, 2006, 03:50 PM

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ok, that first one didn't work, it said something about unknown #include <stdlib> or something, and the secound one did AFTER, i added a ; to the end of cin >> enter gotta watch those statement enders :P

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June 26th, 2006, 07:13 PM

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Code:

#include <iostream>

main() {
   std::cout << "Enter a friggin' number: ";
   int x;
   std::cin >> x;
   //these print the same thing
   std::cout << "You entered " << x << "." << std::endl;
   printf("You entered %d.\n", x );

   system("PAUSE");
}

i didn't include the std namespace so you can see how the I/O functions actually look.

when the compiler spits the "`SYSTEM' undeclared (first use this function)" error out, it should tell you that the compiler has no idea what you're talking about when you give it "SYSTEM." usually this compile error occurs when you spell something incorrectly (like in this example) or when you try to access a variable you haven't previously declared. remember, most programming languages (if not all...) are case-sensitive.

Comments on this post

omrsafetyo agrees: my bad with the upper-case "system"

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Last edited by PunkRocKEVin : June 26th, 2006 at 07:18 PM.

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July 6th, 2006, 12:26 PM

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Quote:

Originally Posted by Legitimize

I recently got into learning C++(by recently, I mean like ten, mabey fifteen minutes ago), I got a compiler, all works well, and I built the typical programmers first program, the hello world bit.

Code:

// my first program in C++

#include <iostream>
using namespace std;

int main ()
{
  cout << "Hello World!";
  cout << "I'm a C++ program";
  return 0;
}

Your code should look like this:

Code:

#include<iostream>
int main ()
{
  std::cout << "Hello World!";
  std::cout << "I'm a C++ program";
  std::cin.get();
  return 0;
}

get() will pause the program until the user gives input, usually by pressing enter.

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July 6th, 2006, 12:47 PM

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im sorry, but that was pretty much a spam post, the topic was old, and several solutions had already been given

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July 6th, 2006, 12:53 PM

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Quote:

Originally Posted by Legitimize

im sorry, but that was pretty much a spam post, the topic was old, and several solutions had already been given

It wasn't months old.. just a few weeks.. and he tried to help.

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