Thread: Tell me about C/C++

Fixed my problem, thanks to A Roxxor

Now time to learn that bastard of a language

Also, nice one slayer.

Here's another version of what slayer posted:

Code:

#include <iostream>

using std::cout;
using std::endl;

int main (void) {

    int a = 0;

    while (a < 10) {
        a++;
    }
    cout << "Congrats, the variable <a> hit 10!" << endl;

    return 0;
}

Just to add some more to study :p

What's the difference between C++ and dev C++

Originally Posted by slash112

Cool, I have downloaded and installed code::blocks. Then it asked me what compiler to use, so I used windows visual C++ since it was already on my computer from last time I tried all this stuff.

My problem now is that it won't build or something, I click build, then I click run, and it says I need to build it. I then tried "build and run" and it just kinda does nothing. Don't know what the fuck is wrong here.

Tell it to use GCC instead, MinGW should be automatically installed with Code::Blocks, and it more standard.

Originally Posted by guitarboy

What's the difference between C++ and dev C++

Dev-C++ is a deprecated IDE, it's not a language or even a compiler. It uses the GCC compiler. The project was discontinued and merged with Code::Blocks.

Originally Posted by slayer

Code:

#include <iostream>
using namespace std;

int main()
{
    int a;
    a = 0;

    if ( a < 10 )
    {
        do
        {
            cout << a << " Adding one." << endl;
            a++;

            if ( a == 10 )
            {
                cout << a << " is the right number!" << endl;
                return 0;
            }

        } while ( a < 10 );
    }
}

Got my loop set up so that if a doesn't equal 10, then it keeps adding to it until it does. Pretty neat stuff right there :3

Cool But you don't need that first if statement. You just assigned a to 0, there is no reason to check if it's less than ten since you know it will be

Originally Posted by ninja9578

Cool But you don't need that first if statement. You just assigned a to 0, there is no reason to check if it's less than ten since you know it will be

But it doesn't really matter if you do, though. It's only one extra comparison. The place you really want to use a do...while is where you need to run the data through at least one literation before you're even ready to test the condition (can't think of such a scenario of the top of my head, though).

Also, instead of writing

Code:

int a;
a = 0;

Why not just write

Code:

int a = 0;

Uses less space and is actually a bit faster.

Code:

#include <isostream>

using namespace std;

int main()
{
     int a, b, total;

     cout << "Enter two numbers here...;" << endl;

     cin >> a >> b;

     total= a + b;

     cout << "Sum equals;" <<Total << endl;

     system(PAUSE) ;

     return 0;
}

returns 7 errors fix it dreamviews!

Originally Posted by guitarboy

returns 7 errors fix it dreamviews!

Code:

/*#include <isostream>

using namespace std;*/

int main()
{
/*     int a, b, total;

     cout << "Enter two numbers here...;" << endl;

     cin >> a >> b;

     total= a + b;

     cout << "Sum equals;" <<Total << endl;

     system(PAUSE) ;
*/
     return 0;
}

Emmmm... doesn't that basically the actual code with :

Code:

int main()
{
     return 0;
}

?

I'm guessing that is some sarcastic way of saying his program can't be fixed?

Ok, I fixed it. Suck it, Ynot .

Code:

#include <iostream>
using namespace std;

int main()
{
     int a, b, Total;

     cout << "Enter two numbers here...;"

     ;cin >> a >> b;

     Total= a + b;

     cout << "Sum equals;" <<Total << endl;

     return 0;
}

I had no idea what I was doing, but it somehow worked

Yeah, C++ is case sensitive.

Originally Posted by guitarboy

Code:

#include <isostream>

It's supposed to be <iostream>, not <isostream> (input/output stream)

Edit: The compiler will also output which lines and expressions were making the trouble. Compiling that you'd first get an error stating that <isostream> couldn't be included in the project, and the subsequent errors came because std::cout and std::cin wasn't defined (the <iostream> header defines these values so you can use them)

I don't understand what it wrong with this. It says "error: expected primary-expression before "else"" and also "error: expected ';' before else"

It is supposed to be that it calculates the radius or circumfrence of a circle if you input the circumfrence/radius.

Have I done something wrong with the if/else thing?

Code:

#include <iostream>
using namespace std;

#define PI 3

int main()
{

double r, d, circle, entered_number;

cout<<"Enter 1 to find circumference, or enter 2 to find radius/diameter"<<endl;

if (entered_number == 1)
cout<<"To find circumfrence of circle, please input radius"<<endl;
cin>>r;
circle = PI * r * 2;
cout<<"The circumfrence of the circle is "<<circle<<endl;

else if (entered_number == 2)
cout<<"To find radius of circle, please input circumfrence"<<endl;
cin>>circle;
r = circle/(PI*2);
d = r * 2;
cout<<"The radius of the circle is "<<r<<" and diameter is "<<d<<endl;

    return 0;
}

EDIT: Fixed it, but there is something wrong somewhere in it, even though it runs... I'll need to find that.

EDIT2: found that problem too... a very obvious one

you've forgotten to group the code propperly. What you wrote is basically

Code:

#include <iostream>
using namespace std;

#define PI 3

int main()
{
double r, d, circle, entered_number;

cout<<"Enter 1 to find circumference, or enter 2 to find radius/diameter"<<endl;

if (entered_number == 1) {
cout<<"To find circumfrence of circle, please input radius"<<endl;
}
cin>>r;
circle = PI * r * 2;
cout<<"The circumfrence of the circle is "<<circle<<endl;
else if (entered_number == 2) {
cout<<"To find radius of circle, please input circumfrence"<<endl;
}
cin>>circle;
r = circle/(PI*2);
d = r * 2;
cout<<"The radius of the circle is "<<r<<" and diameter is "<<d<<endl;
    return 0;
}

When you wanted

Code:

#include <iostream>
using namespace std;

#define PI 3

int main()
{

double r, d, circle, entered_number;

cout<<"Enter 1 to find circumference, or enter 2 to find radius/diameter"<<endl;

if (entered_number == 1) {
cout<<"To find circumfrence of circle, please input radius"<<endl;
cin>>r;
circle = PI * r * 2;
cout<<"The circumfrence of the circle is "<<circle<<endl;

} else if (entered_number == 2) {
cout<<"To find radius of circle, please input circumfrence"<<endl;
cin>>circle;
r = circle/(PI*2);
d = r * 2;
cout<<"The radius of the circle is "<<r<<" and diameter is "<<d<<endl;
}
    return 0;
}

If you want more than one block of code after an if/else/for/while/whatever statement, you need to enclose it in brackets. Also, it's common to indent blocks so that the end result looks like this (but it's strictly optional, C/C++ ignores excess white space)

Code:

#include <iostream>
using namespace std;

#define PI 3

int main()
{
	double r, d, circle, entered_number;

	cout<<"Enter 1 to find circumference, or enter 2 to find radius/diameter"<<endl;

	if (entered_number == 1) {
		cout<<"To find circumfrence of circle, please input radius"<<endl;
		cin>>r;
		circle = PI * r * 2;
		cout<<"The circumfrence of the circle is "<<circle<<endl;
	} else if (entered_number == 2) {
		cout<<"To find radius of circle, please input circumfrence"<<endl;
		cin>>circle;
		r = circle/(PI*2);
		d = r * 2;
		cout<<"The radius of the circle is "<<r<<" and diameter is "<<d<<endl;
	}
	return 0;
}

Makes the code much cleaner, as you can see.

Yea, I had it all fixed up like that. And yea, all my indents went away while editing it so much, deleting, adding in stuff, I ended up deleting all the indents.

I could make the program much better than that, but right now, I'm just using it as a learning thing. Next thing to try is to use the loop thingy (do while?), so that the program stays open and you can calculate more.

You should also loop into while loops and for loops.

Code:

int a = 50;
do{
   std::cout << "I'm inside the loop " << a++ << std::endl;
} while (a < 10);

Code:

int a = 50;
while (a < 10){
   std::cout << "I'm inside the loop " << a++ << std::endl;
}

Have one but very important difference, see if you can figure out what it is

Well, one of them is a while loop, and one is a do while loop. I don't really understand the difference, even after reading about it.

I should look at this page on loops for ages. I have trouble taking in/reading that much information at once, mainly because of a short attention span. I'll just have to try...

Thanks, slash.
How do I run it in a window instead of terminal?

Yea... I was wondering the same thing.

I want to learn how to make a GUI. It isn't necessary at this stage though, anyway.

Originally Posted by ninja9578

You should also loop into while loops and for loops.

Code:

int a = 50;
do{
   std::cout << "I'm inside the loop " << a++ << std::endl;
} while (a < 10);

Code:

int a = 50;
while (a < 10){
   std::cout << "I'm inside the loop " << a++ << std::endl;
}

Have one but very important difference, see if you can figure out what it is

The difference has to do with where the check is made. In the first bit of code, the check doesn't happen until after what's inside the loop has been done, therefore, it ALWAYs gets done at least once, the second piece of code does the check beforehand, so it may never get called

Stick with terminals for now, I'll show you how to make a window a little later.

alright, I wrote a program that gives you the circumference of a circle after you put in the circumference and the approximate of pi.
How can I make it simpler, i.e; tell it that the variable p is 3.14, without you having to put it in.

Code:

#include <iostream>
using namespace std;

int main()
{
     int r, p, Total;

     cout << "Enter radius and pi approximate here... "

     ;cin >> r >> p;

     Total= r * r * p;

     cout << "Circumference is " <<Total << endl;

     return 0;
}

and how do I run it in a window, not terminal

Originally Posted by guitarboy

alright, I wrote a program that gives you the circumference of a circle after you put in the circumference and the approximate of pi.
How can I make it simpler, i.e; tell it that the variable p is 3.14, without you having to put it in.

and how do I run it in a window, not terminal

Code:

#include <iostream>
using namespace std;

#define PI 3.141592654357

int main()
{
     float r, Total;

     cout << "Enter radius here... "

     cin >> r;

     Total= r * 2 * PI;

     cout << "Circumference is " <<Total << endl;

     return 0;
}

First off, ints are just integers, you need decimals for this, so we use float instead. Also, your formula was wrong Circumfrance = pi time diameter, you were calculating area. lol.

#define is what's called a macro, it's not real code. When the compiler compiles your source code, the first thing that it does, it copies and pastes macros. So when the code gets compiled, the literal value of pi gets replaced at all occurrences of PI. It is standard practice to keep definitions in caps, although not necessary.

Nice, guitarboy. It's funny how different I would do it from that. It's amazing the amount of possibilities for one single purpose.

Also, you don't really need a window yet, do you.

Originally Posted by ninja9578

Code:

#include <iostream>
using namespace std;

#define PI 3.141592654357

int main()
{
     float r, Total;

     cout << "Enter radius here... "

     cin >> r;

     Total= r * 2 * PI;

     cout << "Circumference is " <<Total << endl;

     return 0;
}

First off, ints are just integers, you need decimals for this, so we use float instead. Also, your formula was wrong Circumfrance = pi time diameter, you were calculating area. lol.

radius * radius= diameter, times pi

#define is what's called a macro, it's not real code. When the compiler compiles your source code, the first thing that it does, it copies and pastes macros. So when the code gets compiled, the literal value of pi gets replaced at all occurrences of PI. It is standard practice to keep definitions in caps, although not necessary.

Also, you don't really need a window yet, do you.

it would be nice to know how to do it.
And color it.
and change text color.
etc.