Learn C++

you haven’t mentioned what void is yet

[ It was covered in a first look at functions. "A return type of void means the function does not return a value". -Alex ]

When you say two numbers from the user it make it sound like 2 different numbers from the user not adding 1 number to itself by putting it into two variables.

[ I am not sure I follow. The intent is to read in 2 different numbers from the user. Sample program #1 does just that by reading one value into x, and one value into y. These are then added together and sent to the function that writes the answer. -Alex ]

There’s a much easier code for Question 1:

[ Code removed so as not to give hints as to how to solve the problem ]

thx for the tutorial, it really helps

Show me what I’m missing. Why don’t you need to declare “int y” as part of the “int ReadNumber()” function? It would seem that this is necessary since in the main function, both “int x” and “int y” are called. How can “int y” be called if it has not been expressly declared? When the function “int ReadNumber()” was declared at the top of the program, only “int x” was included as part of the declaration. Please explain.

About the function “void WriteAnswer(int)” in question 1):

Since in the main function, the statement:

WriteAnswer(x+y);

does return a value for the addition of x plus y , why does “WriteAnswer” have a type of “void”? Can you provide more clarity on when a function can be of type “void” and return a value such as it does in this case?

Thanks

Hi, Alex!

I just wanted to let you know that quiz question one says to write a function called ReadInteger(), however all of the solutions say ReadNumber() instead.

Once again, I think this is a great tutorial.

[ Thanks for letting me know! It's fixed. -Alex ]

I made a few changes to this program. I took the asking for a number part out of the ReadNumber function, so that i can ask for a first and second number explicitly. I also had the program print the word OK after the user entered a number. Throughout this tutorial, I have been observing the effects of typing in numbers, letters, and even expressions, when it is expecting an integer. You have yet to explain what it does in these cases or how to validate proper inputs. I usually validate inputs in my programs. This is my first low-ish level language, usually deal with higher stuff like MATLAB. I’m sure this all will be explained in later sections. I want to tell you what happens though.

I enter the letter s for the first number. it prints OK to the screen, since there isn’t any validation, it always does. It asks for the second number. But it answers itself with the word OK, and prints the answer as 0. How does s + OK equal 0? we should clear the input buffer every function then?

I am trying to wirte a simple program using on Function, but I am getting following error about stdafx.h.
Please let me now where I am making mistake.

fatal error C1083: Cannot open include file: ’stdafx.h. I will appreciate your help.

I did the first one and to test it I tried compiling it, and at first i thought i was doing something wrong but I can’t compile your code either, I can run it though, and it prints out the solution as expected. I figure I must have forgot something?

I can’t get solution 3 to build.

This is my main ccp (test8.cpp):

// Test8.cpp : Defines the entry point for the console application.

#include "stdafx.h"
#include "io.h"

int main()
{
	int x = ReadNumber();
	int y = ReadNumber();
	WriteAnswer(x+y);
	return 0;
}

This is my io.cpp:

#include "stdafx.h"
#include 

int ReadNumber()
{

	using namespace std;
	cout <> x;
	return x;
}

void WriteAnswer(int x)
{
	using namespace std;
	cout << "The answer is: " << x << endl;
}

And this is my io.h:

#ifndef IO_H
#ifdef IO_H

int ReadNumber();
void WriteAnswer(int x);

#endif

This is the error I get:

c:vcpp2008projectstest8test8io.h(8) : fatal error C1070: mismatched #if/#endif pair in file ‘c:vcpp2008projectstest8test8io.h’

(I’m putting #include iostream with at each side or iostream at the top of io.cpp here and there isn’t supposed to be space between the << after the cout in io.cpp here either, but it won’t display correctly. Slashes won’t show up in the error message either.)

Good job on chapter 1. I’ve really been struggling with stuff like pointers and arrays so I’m going through this whole tutorial slowly. Hopefully the advanced stuff will be as good as this. Thanks for the tutorials!

Can I just put what you have in io.h in stdafx.h? Would that not remove some of the difficulty?

Very useful!!

/* Program of add two number like example 1 */

#include <iostream.h>
#include <conio.h>

int ReadNumber(int x,int y)
{
int z;
z = x + y;
return z;
}

void WriteAnswer(int x)
{
cout << "\n The Answer is " << x;
}

void main()
{
int x,y,z;
clrscr();
cout << "\n Enter the first Number : ";
cin >> x;
cout << " \n Enter the second Number : ";
cin >> y;
z = ReadNumber(x,y);
WriteAnswer(z);
getch();
}

/*End of Program */

This one was very helpful. Thanks. Those tutorials give me some hands on experience (I learn a lot faster that way). Thanks again for the great tutorial.

Hi Alex,

For Problem 1, I actually used 3 “.cpp” files (main, readnumber and writeanswer) and created a header file to make the link. Everything is fine except (yeah I wouldn’t spam this blog if everything were really fine) that it doesn’t compile when I define WriteAnswer() this way:

#include "stdafx.h"
#include <iostream>

void WriteAnswer(int x)
{
using namespace std;
cout << "The sum is: " << x << endl;
}

You did that in chapter 1.8.
The error message I get:

—— Build started: Project: Addition, Configuration: Debug Win32 ——
Compiling…
WriteAnswer.cpp
c:\documents and settings\ben.beni\mes documents\visual studio 2008\projects\addition\addition\writeanswer.cpp(7) : error C3872: ‘0xa0′: this character is not allowed in an identifier
c:\documents and settings\ben.beni\mes documents\visual studio 2008\projects\addition\addition\writeanswer.cpp(7) : error C2065: ‘cout ’ : undeclared identifier
Build log was saved at “file://c:\Documents and Settings\Ben.BENI\Mes documents\Visual Studio 2008\Projects\Addition\Addition\Debug\BuildLog.htm”
Addition – 2 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

But it does compile if I just ask for the output

cout << x << endl;

Another question I’ve got, when I run this through Visual Studio 2008, it automatically pauses after it gave me the answer, asking me to press a touch to continue. But if I run that from the “.exe” created, it won’t stop and closes the window right after I enter the second integer (and press enter). How come?

Thanks.

I can’t get quiz 3 answer to compile. I use Code::Blocks 8.02. I copied and pasted exactly the same code from your post, and it gives the following error:

obj\Debug\main.o||In function `main’:|
C:\temp\CBProjects\IO_Separated_Files\main.cpp|5|undefined reference to `ReadNumber()’|
C:\temp\CBProjects\IO_Separated_Files\main.cpp|6|undefined reference to `ReadNumber()’|
C:\temp\CBProjects\IO_Separated_Files\main.cpp|7|undefined reference to `WriteAnswer(int)’|
||=== Build finished: 3 errors, 0 warnings ===|

I was struggling with the first question a bit, so I had a look at the answer. I didn’t really understand how it worked, but after compiling it myself, I figured it all out.

I’d have never thought to write it like that :P

I just want to say thank you, again, for all of this wonderful-ness!! :) The comments are great, too, for troubleshooting my work/problems and for avoiding problems in the future. I love this tutorial. I am an absolute beginner and I’m finding it fairly easy to grasp.

alex should be nominated as “best man on the net”. this guy like responds, AND COMPILES, everyones problems lol. thanks allexxxx!

Hallo alex,

I am practicing c++ under Linux ubuntu. till yet i compiled my files in the console with the g++ command. but now i dont know how to compile multible files that belong to one projekt. please is there any sugestion for me ?

Whats the point of

# #ifndef IO_H
# #define IO_H  

I understand it’s a headergaurd, but I don’t get what defining IO_H does

nevermind, i didnt see that last #endif and i get it now

How does main.cpp know to include io.cpp if there’s no include statement for it?

I made this code for the first question and this code also works.
But I wanted to know if my code is fine or not.

int x;
int y;

void ReadNumber()
{
        using namespace std;
        cout << "Enter 1st No to be added"  x << endl;;
	cout << "Enter 2nd No to be added"  y <<endl;
}

int WriteAnswer()
{
	return x + y;
}

int main()
{
	using namespace std;
	ReadNumber();
	cout << WriteAnswer() << endl;
	return 0;
}

Well I managed to do question 3 on my own, however I needed help on 2 and especially 1 :P

I keep forgetting when and when not to use a semi colon when declaring/defining functions :S

Also, it gets a bit confusing in the first answer where the ‘int x’ in the “WriteAnswer” function isn’t the same ‘x’ as in the “ReadNumber” or “main” functions…

I would suggest changing it to ‘t’ or something (t for total)

Hej Alex Admin, another question:

I took the innitiative to make a slightly different program after completing this test. But guess what? It doesn’t work. I will post the code because I can’t seem to figure it out.

the main cpp:

#include "stdafx.h"
#include <iostream>
#include "addsub.h"

int main()
{
	using namespace std;
	int a = add();
	int b = add();
	int c = sub();
	int d = sub();
	PrintAnswer(a+b-c-d);
	return 0;
}

the add and subtract cpp:

#include "stdafx.h"
#include <iostream>

int add()
{
	using namespace std;
	cout << "Type a number to add: ";
	int a;
	cin >> a;
	return a;
}

int sub()
{
	using namespace std;
	cout << "Type a number to subtract: ";
	int b;
	cin >> b;
	return b;
}

void PrintAnswer(int c)
{
	using namespace std;
	cout << "The answer is: " << c << endl;
}

the add and subtract header file:

#ifndef ADDSUB_H
#define ADDSUB_H

int add(int a);

int sub(int b);

void PrintAnswer(int c);

#endif

error codes:
1>c:vs2005evencreatiefevencreatiefevencreatief.cpp(8) : error C2660: ‘add’ : function does not take 0 arguments
1>c:vs2005evencreatiefevencreatiefevencreatief.cpp(9) : error C2660: ‘add’ : function does not take 0 arguments
1>c:vs2005evencreatiefevencreatiefevencreatief.cpp(10) : error C2660: ’sub’ : function does not take 0 arguments
1>c:vs2005evencreatiefevencreatiefevencreatief.cpp(11) : error C2660: ’sub’ : function does not take 0 arguments

Thanx for looking it at, hope you see where I went wrong, I really like your tutorials, they make me learn a lot!

my question is is it possible to declare x and declare y
before he main function or i can only declare ReadNumber only once like this

#include <cstdlib>
#include <iostream>

using namespace std;

int ReadNumber()
{
    cout << "Enter a number" << endl;
    int    x;
    cin >> x;
    return x;
}
void WriteNumber(int x)
{
     cout << "WriteNumber(int x)" << x << endl;

}
int ReadNumber()
{
    cout << "Enter a number" << endl;
    int    y;
    cin >> y;
    return y;
}
void WriteNumber(int y)
{
     cout << "WriteNumber(int y)" << x << endl;

}

int main()
{
    int x = ReadNumber();
    int y = ReadNumber();
    cout << "WriteAnswer (x, y)" << (x+y) << endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}

I don’t quite understand the point of having the “io.cpp” file if I use an “io.h” file with the functions declared there instead.

What I did at first was to use just the two files io.h and main.cpp.

My io.h file looks exactly like the example io.cpp file minus the

#include <iostream>

which I took out because it’s called before the io.h file in my main.cpp file.

My main.cpp looks exactly the same. This works fine.

So why do I need to move the contents of io.h to io.cpp and put the forward declarations in io.h? It doesn’t seem necessary and it adds an extra file.

Hope that’s easier for you to read than it is for me. ;)

ive got a problem… when i tried making the code to take 2 numbers and add them i think i did somthing wrong.. can anyone tell me what i did wrong??

#include
using namespace std;

int main()
{
int x;
cout << “can i have your first number please” <>x;
cout << “Thank you” << endl;
int y;
cout << “can i have your second number please” <>y;
cout << “thank you” << endl;
}

int add(int x, int y)
{
cout << “Compiling your numbers……” << endl;
int x + y = g
}

int read()
{
cout << “Your number added to gether is” <<g<< endl;
system(“PAUSE”);
return 0;
}

my error’s are 19 D:\Dev-Cpp\main.cpp expected primary-expression before “int”
19 D:\Dev-Cpp\main.cpp expected `;’ before “int”
D:\Dev-Cpp\Makefile.win [Build Error] [main.o] Error 1

hi, i answered and understood question 1, but when i split the functions into main and io.cpp for the forward declarations of ReadNumber() + WriteAnswer(), getting compile errors all over the place.
First split Main as in the tutorial…
Then added io.cpp into source file….
get the following errors
\projects\io\io\io.cpp(10) : error C2871: ’std’ : a namespace with this name does not exist
\projects\io\io\io.cpp(11) : error C2065: ‘cout’ : undeclared identifier
\projects\io\io\io.cpp(13) : error C2065: ‘cin’ : undeclared identifier
\projects\io\io\io.cpp(19) : error C2871: ’std’ : a namespace with this name does not exist
\projects\io\io\io.cpp(20) : error C2065: ‘cout’ : undeclared identifier
\projects\io\io\io.cpp(20) : error C2065: ‘endl’ : undeclared identifier
1>Generating Code…
1>firstown2 – 6 error(s), 0 warning(s)
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

then i tried commenting out ‘//#include “stdafx.h”‘ in io.cpp

and i get….

\projects\io\io\io.cpp(24) : fatal error C1010: unexpected end of file while looking for precompiled header. Did you forget to add ‘#include “stdafx.h”‘ to your source?
1>firstown2 – 1 error(s), 0 warning(s)
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

dont understand what is going on here, all I did was split the files as in question 2, now it doesn’t work.

Please help me to understand, as I cant move on until I do.

Not sure I completely understand but now works by swapping #include “stdafx.h” with #include

now compiles fine

Just a heads up on the quiz three thing. I was unable to compile the code because my header file didn’t contain

#include "io.cpp"

Or id get an error stating something along the lines of: unresolved symbol something yadda yadda…

Question on linking .cpp files: I was unable, for question 2, to link the main.cpp with io.cpp. When I finally tried changing io.cpp to io.h, and left it in the same folder, it suddenly worked. I am using microsoft visual c++ 2008. I am wondering if there is a problem with #including .cpp files in .cpp files. By the way I love your site!

#include "stdafx.h"
#include
using namespace std;

void Read()
{
	int x;
	int y;
	cout <<"Enter a number: " <> x;
	cout <<"Enter a number: " <> y;
}
int Write(int x, int y)
{
return x+y;
}

int main()
{
	Read();
	cout << Write << endl;
	system("pause");
	return 0;
}

Not sure what I did wrong. It compiles just fine. But when I enter the two numbers, I get random asnwers.

I am terrible at this, just terrible. Time to start from the beginning.

I can’t even get this to work on Visual Studio Express 2008. Is it me or is there a glitch?

#include <stdafx.h>
#include <iostream>

int Main()
{
	using namepsace std;
	cout << "Pick a number" << endl;
	return 0;
}

Thank you for these great tutorials! I’m really enjoying all of this. :]

I wrote a different set of code where WriteAnswer() calls ReadNumber() twice in a sum operation

int WriteAnswer()                                       //defines WriteAnswer()
 {
     int sum=ReadNumber()+ReadNumber();                 //Makes one call to ReadNumber() getting 1st x value
                                                        //and adding that to a second call to ReadNumber() that returns a second x value
     cout << "Your total is: " << sum << endl;
     return(0);
 }

The main function only calls WriteAnswer() one time and the program works fine.
What I would like to know is how to be able to make the program print the return value for ReadNumber() the return is return(x);

Thanks so much for your help with learning this.
I could not have gotten interested without this website.

kinda curious about something, when i tried this i tried

#include <stdafx.h>
#include <iostream>

int ReadNumber(int x, int y)
{
	return x + y;
}

void WriteAnswer(int x)
{
	using namespace std;

	cout << x << endl;
}

int main()
{
	using namespace std;

	cout << "Enter a number: ";
	int nX;
	cin >> nX;

	cout << "Enter another number: ";
	int nY;
	cin >> nY;

	cout << nX << " * " << nY << " = " << WriteAnswer(ReadNumber(nX,nY)) << endl;

	return 0;
}

kinda curious as to why WriteAnswer(ReadNumber(nX,nY)) does’nt work. When i look at it i see ReadNumber returning the value of nX + nY into WriteAnswer(int x). I know how to do this problem another way that works just still curious about this. plz and thx you :)

When I try to build the first program, I get an error (Cube::Blocks) saying “expected initializer before ‘int’ on line 8.

Code:

#include
#include “add.h”

using namespace std;

int add(int x, int y)

int main() // This is the line that had the error
{
cout <> x;
cout <> y;

add(int x, int y)

}

Looking at the other comments, my code is way off and barely complete, but I should at least get this solved for future reference, right?

Hi Alex,
Great tutorial. Is there a general rule for when to define a function with parameters or not? I’m a little fuzzy in that area.

Great tutorials!

Am I right, that in the 1’st Quiz, a

return x;

must also be added to our

int WriteAnswer(int x)

???

Edit: BLEH! Stupid me. It’s void, not int :p

Is this correct?

#include <iostream>

using namespace std;

int ReadNumber(int x, int y);
int WriteAnswer(int x, int y);

int main()
{
    cout << "Please enter a number:" << endl;
    int num1;
    int num2;
    cin >> num1;
    cout << "Thank-you, and another:" << endl;
    cin >> num2;
    cout << "Thank-you..." << endl;
    cout << num1 << " + " << num2 << " =  " << WriteAnswer(num1, num2) << endl;
    return 0;
}

int WriteAnswer(int x, int y)
{
    return x + y;
}

Hey there…this is my first night on here, so beginner on c++ eh. But I thought I did everything correctly, but I am stuck with 1 error.

LINK : fatal error LNK1561: entry point must be defined

Here’s my 3 files:
=============================================================================================================
io.cpp:

#include
int ReadNumber()
{
using namespace std;
cout <> x;
return x;
}

void WriteAnswer(int x)
{
using namespace std;
cout << "The answer is " << x << endl;
}
=============================================================================================================

io.h:

#ifndef IO_H
#define IO_H

int ReadNumber();
void WriteAnswer(int x);

#endif

=============================================================================================================

main.cpp:

#include "io.h"

int main()
{
int x = ReadNumber();
int y = ReadNumber();
WriteAnswer(x+y);
return 0;
}

=============================================================================================================
I do think this is the best tutorial, I unbookmarked some others just because they were not nearly as useful as this…

Much Thanx,
Nick M.

Forgot to tell you I’m using V.S. 2008…if that helps any.

first of all thanks for this site, I really appreciate the step by step help.

My first thoughts when attempting the quiz was “how do i get WriteAnswer() to use the results from ReadNumber()…
Also I would have never thought that ReadNumber() could define only x and be used like this inside main.cpp
So i had to cheat to understand how to accomplish quiz 1.

quick question i got from the above responses. Is using

<> 

when using cin or cout ok?? I notice other have posted doing this.
Again thanks for the site, I am a total beginner but I can now see my goal of creating a task/timekeeper for work might actually be possible.

edit to the above poster i am jsut guessing but maybe your io.cpp

 #include

should be

#include <iostream> 

but I am guessing

That void function is tricky. I worked around it by asking the user for two inputs with different variables and then add them. It works as well, but it wasn’t the assignment.

#include "stdafx.h"
#include <iostream>

int som(int x, int y)
{
	return x+y;
}

int main()
{
	using namespace std;
	cout << "Enter a number: ";
	int x;
	cin >> x;
	cout << "Enter another number: ";
	int y;
	cin >> y;
	cout << "That adds up to: " << som(x,y) << endl;
	return 0;
}

Funny, everyone seemed to be stumped by the same thing I was, the fact that WriteAnswer only had one int but main had two. Before reading posts about this or continuing with the test, I went back to the section on functions and figured it out, but this was a very tricky question to put on the test, since your examples were all (a,b) in both “main” and the “add” and “multiply” functions. I think you should go back to that section and add a blurb about the relationship between main and external functions, because though it all makes sense once you figure it out, this leads to unnecessary head-scratching for us fledgling coders. You could write a pared-down version of your response in an earlier post:

“Hmmm. When we say “int x” or “int y”, we’re telling the program that we’re defining a new variable, and we’re telling the program what type the variable is and what it’s name is. When a new variable is declared inside of a function, that variable’s name is only meaningful within that function. As a result, it is perfectly permissible to reuse the same variable name within multiple functions. This does not imply any kind of linkage between these variables.

Within main(), we declare two variables: x and y. These variables only exist within main(). We need two variables here because we have to hold two inputs.

Within ReadNumber(), we also declare one variable named x. This x has no relationship to the x we declared within main(). In fact, ReadNumber() doesn’t even know that another variable with the same name exists within main(). This is a good thing because it means we don’t have to worry about naming collisions.

We do not declare a variable y within ReadNumber() because ReadNumber() only needs one variable to do it’s job. Once ReadNumber() is finished executing, it passes it’s value back to the caller (main()). Main() then assigns that value to one of the variables it declared.

It might help you understand conceptually if you rename the x variable inside of ReadNumber() to “z”, or some other name that is not reused by main().”

Thank You Jason for your explaination…that really worked for me

hey, great site :)
im using visual c++ 2008

i keep getting this error:
1>—— Build started: Project: Firstquiz, Configuration: Debug Win32 ——
1>Compiling…
1>Firstquiz.cpp
1>Linking…
1>Firstquiz.obj : error LNK2019: unresolved external symbol “void __cdecl WriteAnswer(int)” (?WriteAnswer@@YAXH@Z) referenced in function _main
1>Firstquiz.obj : error LNK2019: unresolved external symbol “int __cdecl ReadNumber(void)” (?ReadNumber@@YAHXZ) referenced in function _main
1>C:\Users\luke\Documents\Visual Studio 2008\Projects\Firstquiz\Debug\Firstquiz.exe : fatal error LNK1120: 2 unresolved externals
1>Build log was saved at “file://c:\Users\luke\Documents\Visual Studio 2008\Projects\Firstquiz\Firstquiz\Debug\BuildLog.htm”
1>Firstquiz – 3 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

any ideas what i can do to fix it?

Is it possible to return two integers with one function?
If so, please demonstrate how. Thanks.

Using the void is tricky.
Kaonashi did just as I did and it worked quite well.
I noticed that Alex’s code doesnt read the second input but simply prints the answer (the sum) immediately you input the second variable.
They both work anyway!
Thanks Alex.

i can’t get the solution of this programme.

my main.cpp is

int ReadNumber();
void WriteAnswer(int x);

int main()
{
int x = ReadNumber();
int y = ReadNumber();
WriteAnswer(x+y);
return 0;
}

io.cpp is

#include “stdafx.h”
#include
int ReadNumber()
{
using namespace std;
cout <> x;
return x;
}

void WriteAnswer(int x)
{
using namespace std;
cout << "The answer is " << x <

error is

LINK : warning LNK4067: ambiguous entry point; selected ‘mainCRTStartup’
1>main.obj : error LNK2019: unresolved external symbol “void __cdecl WriteAnswer(int)” (?WriteAnswer@@YAXH@Z) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol “int __cdecl ReadNumber(void)” (?ReadNumber@@YAHXZ) referenced in function _main
1>C:UsersSanjayDocumentsVisual Studio 2008Projectsjyocpp programmingquiz1.11bDebugquiz1.11b.exe : fatal error LNK1120: 2 unresolved externals
1>Build log was saved at “file://c:UsersSanjayDocumentsVisual Studio 2008Projectsjyocpp programmingquiz1.11bquiz1.11bDebugBuildLog.htm”
1>quiz1.11b – 3 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

i can’t correct this error.pls give some idea.

i can’t get the solution of this programme.

my main.cpp is

int ReadNumber();
void WriteAnswer(int x);

int main()
{
int x = ReadNumber();
int y = ReadNumber();
WriteAnswer(x+y);
return 0;
}

io.cpp is

#include “stdafx.h”
#include
int ReadNumber()
{
using namespace std;
cout <> x;
return x;
}

void WriteAnswer(int x)
{
using namespace std;
cout << "The answer is " << x <LINK : warning LNK4067: ambiguous entry point; selected ‘mainCRTStartup’
1>main.obj : error LNK2019: unresolved external symbol “void __cdecl WriteAnswer(int)” (?WriteAnswer@@YAXH@Z) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol “int __cdecl ReadNumber(void)” (?ReadNumber@@YAHXZ) referenced in function _main
1>C:\Users\Sanjay\Documents\Visual Studio 2008\Projects\jyo\cpp programming\quiz1.11b\Debug\quiz1.11b.exe : fatal error LNK1120: 2 unresolved externals
1>Build log was saved at “file://c:\Users\Sanjay\Documents\Visual Studio 2008\Projects\jyo\cpp programming\quiz1.11b\quiz1.11b\Debug\BuildLog.htm”
1>quiz1.11b – 3 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

i can’t correct this error.pls give some idea.

At first, Thanks a lot for your wonderful and descriptive tutorial. It’s really amazing!
I use Turbo c++ 4.5 (windows version) for writing c++ program(My computer is so old and I can’t install visual studio on it). I write 3 piece of code as you said:
(1)main.cpp

#include "IO1.h"

int main()
{
	 int x = ReadNumber();
	 int y = ReadNumber();
	 WriteAnswer(x+y);
	 return 0;
}

(2)IO1.cpp

#include <iostream.h>
int ReadNumber()
{

	 cout << "Enter a number: ";
	 int x;
	 cin >> x;
	 return x;
}

void WriteAnswer(int x)
{

	 cout << "The answer is " << x << endl;
}

(3)IO1.h

#ifndef IO1_H
#define IO1_H

int ReadNumber();
void WriteAnswer(int x);

#endif

I saved IO1.h in INCLUDE directory. but I don’t know what should else I do?!! There’s no place in tc4.5 like visual studio to add another file to my previous project or I don’t know where it’s. When I compile my main there are these errors :
Linker error : Undefined symbol WriteAnswer(int) in a module MAIN.CPP
Linker error : Undefined symbol ReadNumbera(int) in a module MAIN.CPP

hmm i couldnt do question 1 on my own, so i copied out your code in the answer, but it just flashes and goes away, i tryed putting in
system (“pause”); and stuff, but it still aint working for some reason :/
using DevC++
thanks

i am really grateful for this wonderful tutorial, your response to people’s question has answered mine.
Kiitos!! it means thank you in finnish

Wow, I did it. Thank you so much! The only problem being the site loads up very slow sometimes :[ I understand this is because of how many people are there, but it’s lame :[[

Can some body please help me.
Why does this generate an answer of 2 ever single time (no matter what x,y are)

#include

using namespace std;

int readNumber(int x, int y, int z)
{ cout <> x;
cout <> y;

return z=x+y;
}

void writeAnswer(int z)
{cout << "The answer is : " << z;}

int main()
{
int x,y,z;
readNumber(x,y,z);
writeAnswer(z);
system ("pause");
return 0;
}

#include

using namespace std;

int readNumber(int x, int y, int z)
{ cout <> x;
cout <> y;

return z=x+y;
}

void writeAnswer(int z)
{cout << "The answer is : " << z;}

int main()
{
int x,y,z;
readNumber(x,y,z);
writeAnswer(z);
system ("pause");
return 0;
}

hello i wrote this progam
// io.cpp : Defines the entry point for the console application.
//

#include “stdafx.h”
#include
int ReadNumber()
{
using namespace std;
cout <> x;
return x;
}

void WriteAnswer(int x)
{
using namespace std;
cout << "The answer is " << x << endl;
}

and

// main2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include

int ReadNumber();
void WriteAnswer(int x);

int main()
{
int x = ReadNumber();
int y = ReadNumber();
WriteAnswer(x+y);
return 0;
}

bt they r showin an error to this
like
1>—— Build started: Project: main2, Configuration: Debug Win32 ——
1>Linking…
1>main2.obj : error LNK2019: unresolved external symbol “void __cdecl WriteAnswer(int)” (?WriteAnswer@@YAXH@Z) referenced in function _main
1>main2.obj : error LNK2019: unresolved external symbol “int __cdecl ReadNumber(void)” (?ReadNumber@@YAHXZ) referenced in function _main
1>C:\Documents and Settings\HCL\My Documents\Visual Studio 2008\Projects\main2\Debug\main2.exe : fatal error LNK1120: 2 unresolved externals
1>Build log was saved at “file://c:\Documents and Settings\HCL\My Documents\Visual Studio 2008\Projects\main2\main2\Debug\BuildLog.htm”
1>main2 – 3 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
pl wt s da problem

Alright Alex?

Loving the guide so far, it’s really well written and very helpful and i’ve had no problems up untill now.

But i was wondering, is it bad that i couldn’t figure this out?

I spent nearly two hours trying different things, but didn’t really get close to figuring it out, the only thing i managed to do was build a program that did the same thing but didn’t obide by your rules.

But my question is, should i really know how to do this problem by now? Is it a bad thing that after me seemingly thinking i learned everything so far in your tutorial, i couldn’t put the pieces together and figure out this problem? :)

Thank you alex sir…. Excellent tutorials….

MSVCRTD.lib(crtexe.obj) : error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup

why do i get this error whenever i type the code out myself, i have compared every little tidbit of code and i still get this… any help?

great and xplicit presentation, wonderful lessons, superb back/follow up quiz. this is just it.
THE BEST FREEEEEEEEE!!!! C++ TUTORIAL
THANKS ALEX, U’RE GREAT.

I’m having a problem, and I’m not sure what exactly is going on. I need to have #include “io.cpp” in my io.h file for my program to work. I’m not sure if that’s the way it should be, or if I made a mistake and that #include “io.cpp” is just shunting around the mistake. Here’s my code:
main.cpp

#include <iostream>
#include "io.h"
// add takes two integers as parameters, and returns the result of their sum
// add does not care what the exact values of x and y are

int main()
{
    using namespace std;
    int first = ReadNumber();
    int second = ReadNumber();
    WriteAnswer(second + first);
    cin.clear();
    cin.ignore(255, '\n');
    cin.get();

    return 0;   

}

io.cpp

#include <iostream>
int ReadNumber()
{
    using namespace std;
    cout << "What's the number you want to add?";
    int number;
    cin >> number;
    return number;
    }
void WriteAnswer(int number)
{
     using namespace std;
     cout << "When added, the answer is: " << number  << endl;
}

and lastly, my header file, io.h:

#ifndef IO_H  //IF Not DEFined, then do the following stuff
#define IO_H  //DEFINE name
#include "io.cpp"  //This is the line I can't live without :(
//Definitions here
int ReadNumber();
void WriteAnswer(int number);

#endif //finish up the ol' definition

I know this site went up a while ago, but hopefully someone still reads the comments. Thanks you!

i can’t compile your program even though i pasted it. in both #2 and #3 compiler complains that functions are not defined.

Solution 3 won’t work for me unless I put

#include “stdafx.h”
#include

before putting
#include “io.h”

how come?

I’m confused, in the main function where you declare

    int x = ReadNumber();
    int y = ReadNumber();

Is that ReadNumber() a function call or a value? If it’s a value (which I assume) then I don’t see the part where there’s a call to ReadNumber() from main(), so it must be a call? But I didn’t know calls could be used as a variable value though? Has this been covered in a previous section or have I missed it?

HI, So can someone give me other quizzes too because sucked at these.