very new to c++, and having trouble... plz help

[l2andyl2hoads]

i recently (today) got "dev c++" to start learning c++. just to get started, i made this code to test things out...

Code: Select all

#include <stdio.h>

int main()
{
    printf("Hello world!\n");
    return 0;
}


keep in mind, i am working with dev c++ and in vista. when i compile it, then go to run it, it comes up for a split second and then goes away... can anyone provide a little bit of troubleshooting please?

[fashizzlepop]

It works. Nothings wrong with it. It's supposed to do that. Run it from the command line and it won't dissapear.

[l2andyl2hoads]

first of all, thank you very much for the help.

second... run it from the command line? upon downloading dev c++, they give you example codes. just to see, i opened them and ran them. they work fine and don't go away either. anyway, i digress. what/where is the command line (in dev c++)?

[Kurushimi]

I know you're problem. The reason it comes up and exits is because when the program is completed, it automatically exits. To stop this, just do this:

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#include <stdio.h>

int main()
{
    printf("Hello world!\n");
    system("PAUSE");
    return 0;
}

the "system()" function takes the string you give it as an argument and makes it as though you wrote it as a command in the command prompt. Writing the "pause" command in the command prompt forces the computer to...well, pause, and wait for you to hit a key. So, the above program will display:

Hello World!
Press any key to continue . . .

====

The second option, as the person before me said, would be to run it from the command prompt. To do this, you simply open command prompt and navigate to the folder where the executable is created after the program is compiled. (your computer should come with help on this if you don't know how to do this). Then simply type the name of your program and hit enter.

[l2andyl2hoads]

thank you very much. I'm pretty decent with computers and some stuff that is brought up here on HTS, but for some reason haven't picked up c++ until today. Once again, thank you for your patience on dealing with such a minute problem

[Kurushimi]

No problem. This bugged the heck out of me too.

[l2andyl2hoads]

i completed the simple code as shown before and made several new ones for some math

now i am trying to combine if statements with the math so that i can choose what operation to perform. i don't know if i have gone about this all wrong, but i have received the "antiquated or deprecated" error. anyway, here is the code. once again, help much appreciated

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#include <iostream.h>

int main()
{
     cout<<"Input two numbers..."<<endl;
     int var1;
     int var2;
     int var3;
     cin>>var1;
     cin.ignore();
     cin>>var2;
     cin.ignore();
     cout<<"What operation would you like to perform? \na=add\ns=subtract\nd=divide\nm=multiply"<<endl;
     char var4;
     cin>>var4;
     cin.ignore();
     if (var4='a')
        var3=var1+var2;
     if (var4='s')
        var3=var1-var2;
     if (var4='d')
        var3=var1/var2;
     if (var4='m')
        var3=var1*var2;
     cout<<var3<<endl;
       
     cin.get();
     return 0;
}



EDIT: ok... so i've changed it a little bit to remove unnecessary code and attempt to fix it (i think)... btw, it "works", but all answers are multiplied though...

[kSevis]

Hmm, let me rewrite it a little for you... I think all the four ifs are run.

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#include <iostream.h>

int main()
{
  int var1, var2, var3; //Same effect. I find it looks neater if variables like these are declared in the beginning of the file, but it\'s a personal thing.
  char var4;
  cout<<"Input two numbers..."<<endl;
  cin>>var1;
  cin.ignore();
  cin>>var2;
  cin.ignore();
  cout<<"What operation would you like to perform? \na=add\ns=subtract\nd=divide\nm=multiply"<<endl;
  cin>>var4;
  cin.ignore();
  switch (var4) {
    case 'a': //same as your ifs, as far as I understand.
      var3=var1+var2;
      //cout << "Adding" << endl;
      break; //The breaks are there to separate the cases.
    case 's':
      var3=var1-var2;
      //cout << "Subtracting" << endl;
      break;
    case 'd':
      var3=var1/var2;
      //cout << "Dividing" << endl;
      break;
    case 'm':
      var3=var1*var2;
      //cout << "Multiplying" << endl;
      break;
    default:
      cout << "Action not recognised!" << endl;
      break;
  }
  cout<<var3<<endl;
  cin.get();
  return 0;
}


Try this code. If it still shows the same, uncomment the four cout lines I put, and see if it outputs doing all four actions (or less, if you start with subtracting.)

Another way to solve this would be to not declare var3, and instead use:

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var1 += var2;
var1 -= var2;
var1 /= var2;
var1 *= var2;


In place of your var3 = ... lines. In the case that it isn\'t working, it\'ll output var1 as it was if you add, with a slight possible rounding to the closest var2.

[BhaaL]

Hmm, let me rewrite it a little for you... I think all the four ifs are run.

One thing you have to keep in mind with C-style Languages (that are, but not limited to: C++, C#, PHP, Perl, ...) is that there is a difference between = (assignment) and == (comparison).

Writing the following assigns 'a' to var1, and assignments are always true (except when the value assigned evaluates to false):

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char var1 = 'x';
if (var1 = 'a')
//var1 is now 'a'

The following is what you actually wanted, comparing the value of var1 to 'a':

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char var1 = 'x';
if (var == 'a')
//var1 is 'a'
else
//var1 is not 'a'

[Jack The Ripper II]

Every time i write any C++ code like "#include <stdio.h>

int main()
{
printf("Hello world!\n");
system("PAUSE");
return 0;
}
it says 16 bit MS-DOS Subsystem the NTVDM CPU has encountered an illegal instruction and it has options of close or ignore and either one closes it what do i do?