C / C++ / MFC

28-Mar-02 14:57

Ok,... I finished a bunch of more reserch and these are the things in which i either didnt exactly understand or just questions at random about certain things that i would like to know...

To organize this, if you want to: write the thing that you are weilling to help with in the subject for the reply. "This will make it easier to reply to your answers Smile | :)

" And for any other newbie around may find help in this thread.

~Hex Dec Oct: What is the differance and why use them seperat from each other.

~Globals: How do you decalare a global inside of a little program? or change them around? I had my main program read through somthing that looked like this...

int main()

if(boolone = true);first();
if(booltwo = true);second();

and so on...

then i wanted it so that when your inside of the program first, there would be a gets or cin and if you typed in one off, the program would set the boolone to false and the program wouldnt read anything in there. I could have done somthing extreamly wrong and stupid in the program, but everything checked out and it still didnt work...

~MFC - C++: Ive asked this question before... im going to build a game engine that would allow me to build 2D games that i would like to host over the internet... The engine i would like it to be all in windows, but what language or toolkit should i use? MFC or C++, what one would give me more flexibility and make the job allot less work than it already seems to be?

~Null: Ive seen the 'null' statement used all the time, but i dont know what it is used for. "i think this is a vary newbie question but you know Smile | :)

"

~Clear Screan: When ive bean building line based games in DOS ive always wanted to clear the screan for that the game would look slightly better... How do i do this? "Ive asked this one before also sodo be annoyed Smile | :)

"

~Switch (break and continue): I understand the switch "I think" but im not to sure on break and continue commands... How do i use them?

~Delete: how do i use this? and what is the syntax?

~Public: I looked this one up, but didnt understand. Public: its not a goto statment is it? (dont think so) why use this? also, there is a private: one, how do you use these and why?

~return: Return like in the int main() and return 0; i understand, but... there is other things that you can do with the return statment that i dont quit get... can any one help?

~Get line: What does a get line do? and what is the syntax for doing so?

~#if and #define and #endif #else... : why is there a # sign on these? and the define, what does it do, or what is its purpose?

~std::stream: What does this do?
~std::fstream: what does this one do, and what is its differance to the other one?
~if stream and stream: what do these do? "these last ones are just a (curiosity) and could probably help allot in the future.

~Class: what is a class used for?

~Sound: I really desire to make a sound engine for my game, "and if not in my game" just somthing that would be fun to program and mess around with. But i dont know exactly where to start with the sound and how to send sound to the speakers. Can anyone help in this?

Well, thats all, "allot of questions like i said" but this is like a week of reading and toiling with out asking any at all Smile | :)

" Some of the questions may be stupid and some maybe so lame or easy that maybe a quick syntax would help Smile | :)

Sorry for the annoyance "to those who this annoys..."

Thanks all for hum responds... and for viewing this thread.

~SilverShalkin

Rose | [Rose]

I did have a cool poem that i made up, but Rose | [Rose]

i left it in my graphics class, and the last Rose | [Rose]

time that i posted, i reposted it on a poetry forum Rose | [Rose]

and they said it sucks "that was them being Rose | [Rose]

nice... So next one, after posting it onto the Rose | [Rose]

poetry forum, ill post it here Smile | :)

Tim Smith28-Mar-02 14:59

Tim Smith

28-Mar-02 14:59

~ Hex, Dec, Oct... First, you have to remember that everything to a computer is just a binary number. Hex, Dec, oct are just different ways we use to make those binary numbers readable to humans. Decimal is what we are use to from our youth. Hex is very handy with 8bit systems where 2 hex digits represent the byte of data. Octal is really an outdated system.

Tim Smith

I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?

SilverShalkin28-Mar-02 15:26

28-Mar-02 15:26

Tim Smith wrote:
Hex is very handy with 8bit systems

Ill keep that in mind Smile | :)

so.. i shouldnt really bother with octals?

Thanks for your time

~SilverShalkin

Srcatch another Smile | :)

Christian Graus28-Mar-02 16:13

Christian Graus

28-Mar-02 16:13

SilverShalkin wrote:
i shouldnt really bother with octals?

The key thing is that unless you're displaying the values, the computer doesn't actually care, it's just going to turn it into binary anyhow.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- Jon Hulatt, 22/3/2002

globals

Nish Nishant28-Mar-02 15:01

Nish Nishant

28-Mar-02 15:01

globals are variables or objects that are available to a whole program rather than to just a function or a class., You declare them outside any function or class. Now the whole application can use it. If you have multiple source files you'd have to redeclare them in each of thise files using extern.

Nish

I am the Keyboard Smasher

Re: globals

SilverShalkin28-Mar-02 15:23

28-Mar-02 15:23

you redefine the globals with extern? could you use that in an example? or does it look something like...
int first();
bool one = false;
int main()
{
first()
}

first()
{
extern one "Im just guessing Smile | :)

"
}

Thanks...

~SilverShalkin

Scratch one Smile | :)

Re: globals

Nish Nishant28-Mar-02 15:28

Nish Nishant

28-Mar-02 15:28

Let's say you have two files

a.cpp and b.cpp

Now if you have an int y in a.cpp and an int y in b.cpp, they'd be two separate ints. The idea of a global is to make it application global.

This instead of int y you should declare them as extern int y which tells the compiler than this variable has external linkage. Thus in the final executable this will be a single global variable

Nish

I am the Keyboard Smasher

Jon Sagara28-Mar-02 15:28

Jon Sagara

28-Mar-02 15:28

SilverShalkin wrote:
~Hex Dec Oct: What is the differance and why use them seperat from each other.

Hex: base-16 number system. Valid "digits" are 0-9 and A-F (A=10, B=11, .., F=15). More convenient to use and easier to read than binary.
Dec: The number system you've used since you started learning.
Oct: base-8 number system. Valid "digits" are 0-7. Alternative format for binary number. Used with the Unix command chmod, for example.

SilverShalkin wrote:
~Switch (break and continue): I understand the switch "I think" but im not to sure on break and continue commands... How do i use them?

Compares discrete values. For example, if you have a set of integers, you can handle each case separately:

switch(someValue)
{
   case 0:
      // do something
      break;
   case 1:
   case 2:
      // Do the same thing for 1 and 2
      break;
   default:
      // If not 0, 1, or 2, provide a default code path.
      break;
}

break in this case breaks you out of the switch statement so that, if someValue == 0, you don't keep executing the handlers for 1/2 and the default. break will also break you out of a loop.

continue will take you back to the top of a loop without having to execute it all the way to the end. Useful if you know that you don't want to finish processing an iteration, and you just want to move on to the next one.

SilverShalkin wrote:
~Delete: how do i use this? and what is the syntax?

Use this to free memory you created dynamically on the heap.

char *pChr = new char; // One new character created dynamically on the heap.
delete pChr; // Free the memory held by pStr (the char on the heap).

char *pStr = new char[256]; // An array of 256 chars on the heap.
delete [] pStr; // Free the block of memory (that's what [] is for).

You could also use NULL here. Since you can't reference the memory that both pChr and pStr used to point to, you should set the to NULL (i.e., nothing).

pChr = NULL;
pStr = NULL;

Jon Sagara

There is no spoon.

Best Miniputt score: 21

Jon Sagara28-Mar-02 15:32

Jon Sagara

28-Mar-02 15:32

SilverShalkin wrote:
~Public: I looked this one up, but didnt understand. Public: its not a goto statment is it? (dont think so) why use this? also, there is a private: one, how do you use these and why?

By default, methods and members of classes are private. In order to make them accessible outside of the class, you need to declare them as public.

class CMyClass
{
   // Anything here is private.
public:
   // Anything here is public.
protected:
   // Anything here is protected.
private:
   // private again.
public:
   // public again.
};

I'm tired. I'm going home. Maybe someone else can pick up where I left off. Smile | :)

Jon Sagara

There is no spoon.

Best Miniputt score: 21

Christian Graus28-Mar-02 16:11

Christian Graus

28-Mar-02 16:11

SilverShalkin wrote:
Hex Dec Oct: What is the differance and why use them seperat from each other.

The difference is what base they use. We use decimal because we have 10 fingers, so it was natural in the evolution of math that we consider 10 to be the number that requires one more significant figure. Computers think in binary, which meshes nicely with base 8 (octal ) and base 16 (hex). I've never seen oct used for anything in particular.

The Windows calculator program can show you how the same number is displayed in the different bases, or look at my ostringstream article for a way to stream a number out as different bases. It works the same way if you're just streaming to cout.

SilverShalkin wrote:
Globals: How do you decalare a global inside of a little program?

Just by declaring it. Any variable declared outside of a class or function is global. When you're doing it in C++, the best way is to use extern, which tells the compiler a variable exists, but does not declare it. use extern int i in stdafx.h, and int i in stdafx.cpp to make a variable visible everywhere.

You would be foolish not to wrap such variables in a namespace, so that they have some protection from corruption. Even then, avoid globals if you can.

SilverShalkin wrote:
MFC - C++: Ive asked this question before... im going to build a game engine that would allow me to build 2D games that i would like to host over the internet... The engine i would like it to be all in windows, but what language or toolkit should i use? MFC or C++, what one would give me more flexibility and make the job allot less work than it already seems to be?

MFC is a library that you use in C++, you probably mean MFC or Win32. MFC will take a lot of work away because of the stuff it gives you for networking and so on, but I'd suggest Win32 with DirectX, because you'll need DX anyhow for DirectDraw, and it gives you the networking stuff as well, in DirectPlay.

SilverShalkin wrote:
Null: Ive seen the 'null' statement used all the time, but i dont know what it is used for. "i think this is a vary newbie question but you know

A pointer that does not point to a valid address should point ot 0. Calling delete on such a pointer will not do anything. NULL is a #define, it equates to (void*) 0.

SilverShalkin wrote:
Switch (break and continue): I understand the switch "I think" but im not to sure on break and continue commands... How do i use them?

You don't use continue in break statements. If you don't use a break in a switch, it falls through, like this:

int i = 0;

switch (x)

case 0:
i = 7;
default:
i = 10;

In this case i will always equal 10, because even the case 0 will fall through and the defaul will also execute.

contine and break are used in loops, break stops the loop and continue jumps to the next iteration, so the loop continues but any other code is not executed for this iteration only.

SilverShalkin wrote:
Delete: how do i use this? and what is the syntax?

If a variable is a pointer, then it vecomes an object when it is created with new, and the memory is deallocated and the destructor called when delete is called. You should also set this pointer to NULL.

int * p = new int;
*p = 7; // NOT p = 7, that sets the memory address, not the value )
// use p
delete p;
*p = 5; // ERROR - memory is deallocated
p = NULL;

SilverShalkin wrote:
Public: I looked this one up, but didnt understand. Public: its not a goto statment is it? (dont think so) why use this? also, there is a private: one, how do you use these and why?

In a class, you have functions and members. Anything that is public is visible by anyone who has an instance of a class. private is visible only to the class itself. Often variables are made private and exposed through methods that can validate the data being put into a variable. For exmaple if 0-100 is a valid range for a variable, the closest I can get is a char or unsigned char, but I need to validate the values coming in, or I could get values between -127 and 127, or 0 and 255.

SilverShalkin wrote:
return: Return like in the int main() and return 0; i understand, but... there is other things that you can do with the return statment that i dont quit get... can any one help?

All you can do is return a value. What don't you get ?

SilverShalkin wrote:
~#if and #define and #endif #else... : why is there a # sign on these? and the define, what does it do, or what is its purpose?

Because they are processed by the preprocessor. They can be used to create different versions ( such as debug and release ) or to create macros. The preprocessor uses them to decide what code is passed to the compiler.

SilverShalkin wrote:
~std::stream: What does this do?
~std::fstream: what does this one do, and what is its differance to the other one?
~if stream and stream: what do these do? "these last ones are just a (curiosity) and could probably help allot in the future.

Is there a std::stream ? Surely it's a base class. IOStreams are part of the standard library. A fstream is a bidirectional file stream, ofstreams and ifstreams also exist. Read my article on ostringstream - ofstream works the same way, and both work the same way as cin/cout.

SilverShalkin wrote:
Class: what is a class used for?

To encapsulate a block of logic. For exmaple, MFC has a CPoint class, it encapsulates the data and operations one might do on a point. I can create an instance of a CPoint and I can add them together, compare them, etc. It's a powerful tool to hide implimentation details from users of an object, and also simple to organise code.

SilverShalkin wrote:
Sound: I really desire to make a sound engine for my game, "and if not in my game" just somthing that would be fun to program and mess around with. But i dont know exactly where to start with the sound and how to send sound to the speakers. Can anyone help in this?

For games you should use DirectSound, so you can play more than one sound at the same time.

SilverShalkin wrote:
Well, thats all, "allot of questions like i said" but this is like a week of reading and toiling with out asking any at all " Some of the questions may be stupid and some maybe so lame or easy that maybe a quick syntax would help Sorry for the annoyance "to those who this annoys..."

Anyone who gets annoyed that you're trying to learn something is best ignored, not apologised to. The number of questions probably means I've given brief answers, but just ask if no-one here has yet clarified any of these points sufficiently.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- Jon Hulatt, 22/3/2002

SilverShalkin28-Mar-02 17:30

28-Mar-02 17:30

Thanks guys, the info that ive recieved is going to help allot Smile | :)

Im off to program a little more and ask questions a little less "I dont know if that'll ever happend though Smile | :)

"

~There is an end, when you cant learn any more... isnt there?

Thanks Again!

~SilverShalkin

ps... To those whom this annoys,...

Rose | [Rose]

I see thee no more Smile | :)

Christian Graus wrote:
Anyone who gets annoyed that you're trying to learn something is best ignored, not apologised to.

Rose | [Rose]

right when you think you have Rose | [Rose]

learned it all, there is always Rose | [Rose]

somthing that'll come allong just Rose | [Rose]

to annoy you. I guess thats why Rose | [Rose]

programming could be considered as the Rose | [Rose]

unsolvable puzzle Smile | :)

where you recieve a peice of the picture Rose | [Rose]

ever so often but still have thousands Rose | [Rose]

of peices left. Rose | [Rose]

alex.barylski28-Mar-02 19:39

alex.barylski

28-Mar-02 19:39

SilverShalkin wrote:
~There is an end, when you cant learn any more... isnt there?

IMO

Other than when your dead...nope... Smile | :)

Programming is like:

The more you know, you more you realize the less you know.

Smile | :)

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Nish Nishant28-Mar-02 20:55

Nish Nishant

28-Mar-02 20:55

HockeyDude wrote:
Other than when your dead...nope...

Hockey

I think what he meant is that once you get too old you cannot learn anything more, not that you reach a stage where there is nothing more to learn. I might be wrong though, in which case, your statement that till death, human beings can learn and learn and learn is correct Smile | :)

Nish

I am the Keyboard Smasher

alex.barylski28-Mar-02 22:12

alex.barylski

28-Mar-02 22:12

Age doesn't have a bearing on anyones ability to learn I don't think.

Certainly some go crazy, but even crazy people probably learn...like OUCH better not smash my head into the wall like that again...

Everything/body learns until the end, then it's your guess against mine to what happens after that. Maybe it's like the Matrix and we come back and learn some more...?

Cheers!

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Mazdak28-Mar-02 21:09

Mazdak

28-Mar-02 21:09

HockeyDude wrote:
Programming is like:

The more you know, you more you realize the less you know.

Not Only programming Hockey,everything..everything. Cool | :cool:

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

IIsWebVirtualDir and using the Internet Information Services?

alex.barylski28-Mar-02 22:08

alex.barylski

28-Mar-02 22:08

I knew somebody was gonna jump on me for that. Smile | :)

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Craig Miller28-Mar-02 12:48

Craig Miller

28-Mar-02 12:48

Hi,

I'm trying to programmatically create some virtual directories for a release process and I've run into a strange problem. If I create the virtual directory using the Internet Information Services control panel, the directory is fine and it has an icon of a box with a ball coming out of it. If I use the code shown below, it looks like it creates an application instead of a virtual directory like I think it should. The resulting icon is a folder with a little world on the right lower corner.

Can anyone see what I'm doing wrong with the code below?

Thanks in advance,

Craig

USES_CONVERSION;
try
{
HRESULT hr; // Generic COM result variable
_variant_t variant; // Variant used to set some properties in the metabase
IADsContainer* virtDirRoot; // Virtual root
IADs* virtDir; // The new virtual directory
IDispatch* pDisp = NULL;

//
// Get the virtual directory root
//
hr = ADsGetObject(L"IIS://Localhost/W3svc/1/ROOT",
IID_IADsContainer,
(void**) &virtDirRoot);
if(FAILED(hr))
{
return hr;
}

//
// Create the new virtual directory
//
_bstr_t virtPath("c:\\inetput\\wwwroot\\Test");
hr = virtDirRoot->Create(L"IIsWebVirtualDir", // Name of the virtual directory schema class
L"Test", &pDisp); // Relative name of the object to create
if(FAILED(hr))
{
IErrorInfoPtr error;
HRESULT hr;

CComBSTR description;
hr = GetErrorInfo(0, &error);
if (SUCCEEDED(hr) && error != NULL
&& SUCCEEDED(error->GetDescription(&description)))
{
//return description;
}
}

// Get the IADsContainer interface
hr = pDisp->QueryInterface(IID_IADs, (void**) &virtDir);

// Set the AspAllowOutOfProcess switch
variant = L"true";
virtDir->Put(METABASE_ALLOW_OUT_OF_PROC_COMPONENTS, variant);
virtDir->Put(L"AccessExecute", variant);

// Set the physical path
variant = physDirPath;
virtDir->Put(L"Path", variant);

//
// Set the info
//
virtDir->SetInfo();

return 0;
}

beginning a thread : MFC vs direct API

28-Mar-02 11:36

Using the MFC fn AfxBeginThread requires:

UINT MyFunc(LPVOID);

But using the API call CreateThread requires:

DWORD WINAPI MyFunc(LPVOID);

whats going on here?

Tomasz Sowinski28-Mar-02 11:36

Tomasz Sowinski

28-Mar-02 11:36

AfxBeginThread calls internally CreateThread. But the address of your function isn't passed directly to Win32 API. In the middle there's also CWinThread object which accepts a function with slightly different header.

Just step into AfxBeginThread with the debugger and you'll see the details.

Tomasz Sowinski -- http://www.shooltz.com

- It's for protection
- Protection from what? Zee Germans?

28-Mar-02 12:06

hmm I checked the code. AfxBeginThread actually ends up calling _beginthreadex.
If I guess right, this is cos of the extensive C library calls MFC makes.
Someone please clarify this. sigh.

Tomasz Sowinski28-Mar-02 12:11

Tomasz Sowinski

28-Mar-02 12:11

Satheesh wrote:
AfxBeginThread actually ends up calling _beginthreadex.

Make one step further. Step into _beginthreadex and you'll see the light (I mean, the CreateThread call). FYI, it'll be line 125 of THREADEX.C (on VC6 SP5).

MFC needs to prepare a environment for its thread. It's done via CWinThread object. And - since MFC is a C++ library, it needs to create threads with _beginthreadex to ensure that CRT works OK.

Tomasz Sowinski -- http://www.shooltz.com

- It's for protection
- Protection from what? Zee Germans?

Tim Smith28-Mar-02 12:19

Tim Smith

28-Mar-02 12:19

Too bad there aren't thread creation vectors you can set so that when a thread is created, the routine gets called automatically. Then MFC and CRT can install their own vectors and we could all call CreateThread. Smile | :)

Tim Smith

I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?

Tomasz Sowinski28-Mar-02 12:25

Tomasz Sowinski

28-Mar-02 12:25

If you're a perverse enough process, you can probably launch yourself as a debugee and use WaitForDebugInfo.

Tomasz Sowinski -- http://www.shooltz.com

- It's for protection
- Protection from what? Zee Germans?