[Stavros]

Having almost finishing C++ class, I really wish I had taken WuChild's advice and taking Visual Basic first. I must say, though, that I thoroughly enjoyed my C++ class.

Aside from learning order (Like learning Functions before Arrays) This is pretty much the way our class was structured.

Overall, if you've got the guts, C++ really isn't all that difficult.

[maddog39]

You should probably also note that the first few chapters wont work on any type of unix, because the system command PAUSE doesnt exist in a unix shell or bash for that matter.

[ShadowPho]

Somebody please send me a PM in exactly 2 weeks and I will write a sequel to this. I am just afraid that I will forget about it.

[Shelnutt2]

Originally Posted by ShadowPho

Somebody please send me a PM in exactly 2 weeks and I will write a sequel to this. I am just afraid that I will forget about it.

You got it!

[ShadowPho]

- I love C/C++, so here is a continuation of the tutorial.
Warm-Up lesson
If your program has a loop, then it might take up 100% of the CPU. To avoid that use

Code:

sleep(how long, in unsigned long, ms);

That command tells the CPU to forget about your program for ms time and then come back. So if I do sleep(1000); then your program will pause at that place for ~1 second while the CPU goes ahead and either idles or works on other programs. It is a good idea to have a sleep command in a loop if your program does not need full use of the CPU.
For example, I am working on a cryptographic instant messenger ( so I could chat with my friends without being afraid of RIAA listening in). We don't want it to eat all the CPU resources. So we are telling it to check for incoming messages every 50 ms. (sleep(50)

Random Tidbit
NULL or null is actually 0 in C++. They are exactly the same thing, which is why it is safe to use 0/NULL interchangeably. It is actually declared in one of the header files that NULL is 0. (or is it (void*) 0? )

In java it is NOT the same thing. I learned it the hard way...
Lesson 8 – structures.
What if we are coding a game and want to have some kind of a place to store the status of lets say.... players in a game? We would use a structure. A structure is simply a combination of different types of variables. Here is an example:

Code:

 struct player {  char name[24]; int life; int numberOfPiecesLeft; float location}

The above code will create a structure player that has the specified variables in it. It groups them together. After we declare the structure, we can now declare the actual data storages. You can have structures inside of structures, functions and classes.
So we will do:

Code:

player pl1; player pl2;

Then we will have pl1 and pl2. Now, in order to access a variable in a structure we use periods. So if we want to initialize the top code, we will do:

Code:

pl1.life=100; pl2.life=99; pl1.numberOfPiecesLeft=1;...

This is also used in a lot of headers by different headers/OSes. For example,

Code:

//from winsock2.h
struct sockaddr_in {
        short   sin_family;
        u_short sin_port;
        struct  in_addr sin_addr;
        char    sin_zero[8];
};

So, if we want to have a sockaddr_in, we would do something like this:

Code:

 sockaddr_in mySocket;
mySocket.sin_family=2;
mySocket.sin_port=122;
mySocket..sin_addr.WhateverIsInsideOfSIn_addrStruct;

Lesson 9 – memory/pointers, in theory
Just what is memory? Computers' current memory is a sequence of 1's and 0s that are represented differently. You probably knew this already. So... what does that mean for you? Well, lets look at something you got familiar with: the integer. If you do int myInty = 0, then what does the PC see? It sees 4 bytes (so 32 bits). It sees 0000 0000 0000 0000 0000 0000 0000 0000. Now, you do not need to learn how to convert, because if you will use it then you will remember it.
Now if we have a char ohMyChar. Thats one byte, so it would be 0000 0000.
Pointer. They come next. A pointer is just that – it POINTS to the memory address. In itself, its usually an int size. So, on my system all my pointers are 4 bytes. Example: if I declare this...

Code:

 int realInt=200;  
int *ptr = &realInt;

realInt is just a location that contains 200. ptr is a number (like 0x22ff6c) that the CPU reads to get to that number. *ptr will give back 200.
Pointers are actually numbers that hold a value of the memory they are accessing. But in order to have the memory to use we have to either tie a pointer to somewhere (like above) or ask the OS to give us RAM.
Lesson 10 – The Big Ones, lesson 9 in practice
Normally if you define data for your program, it gets taken from stack. But if you want to be able to allocate RAM while your program is running, you would need to do that manually.
Here is what you do need to learn: malloc/calloc/realloc , and free.
Believe me, asking OS for RAM is extremely easy. The hard part is giving it back appropriately and actually using the RAM. The easiest way to explain this would be to use an example.
So, relax and enjoy the story.
You are the lead programmer of google. You are given an assignment: read some information from a file. So you go ahead and google (oh, the irony!) for C++ file handling. Then you open the file and think about where you are going to store all that information to. You could do something like

Code:

char buffer[1024];

But what if the file is 1025 bytes in length? So you decide that you need to malloc some RAM from Windows/ Linux. Requesting memory from OS is really easy, all you do is

Code:

 malloc(howMuchRamYouWantInBytes);

and the OS will gladly return a pointer to that RAM. If the pointer equals NULL/0 then you know that you wanted too much or the OS did not like you well enough (not enough RAM).
Now, in C++ (unlike JAVA) OS will attempt its hardest to give you all you ask it for. If you accidentally ask the OS for 1 gig of RAM, then it won't ask you what you need it for. It will happily allocate 1 gig of ram and send a pointer that points to one gig of RAM your way.
If you want to see the effect that it can have then try the following code while looking at your task manager RAM usage. And be ready to kill the program once it eats some RAM. After you kill it, Windows will attempt to clean up all wasted RAM.

Code:

while(1)
    {
    malloc(1000*1000); // eat some RAM
    Sleep(100);              // But not too fast
    }

Now that you have seen the following example, make sure never to code the above way. . There a couple ways of rules you have to follow. Here is what good malloc usage has to be:

Code:

int/char/long/struct...   *myPtr  = malloc(amountOfStuff * sizeof(int/char/long...));
if(NULL== myPtr) // if malloc returns 0/NULL, then something bad happened
{ // throw an out of RAM error with report of how much ram you tried to eat 
}
//Use myPtr data here.
free(myPtr); // Frees the RAM. A MUST step

So, by now you know how to ask OS for RAM and how to receive it. You also know the free(ptr), which gives memory back to OS.
The only thing left for the lesson is calloc and realloc.

Code:

 ptr = calloc(number of stuff to do, bytes of each stuff);

That is then initialized to 0.

Code:

 ptr = realloc(ptr, size- same as malloc);

Realloc is a much more interesting function it allows for us to increase or decrease the RAM usage as needed. So, lets say that we have a pointer that points to 20 Mbs of RAM. Now we only need 10 Mbs. A call to realloc will free the last 10 mbs without touching the first 10

Lesson 11, or what we actually do with those
Soon to come. - memset, memcpy, memmove and the usage of RAM by malloc.

[sreeja]

The information about programming in c++ and java is very useful. C++ is a compiler oriented language and java can be complied or interpreted.Therefore java is more suitable than c++.Is it?

[Adak]

Java has it's uses, and C++ has it's strengths. As a programmer, you need to learn the strengths of the languages, and use the one that is most appropriate for the program you intend to write.

C++ would be a good choice for a computationally intensive program, that had to execute with maximum speed, and had an OOP design. It has a power that even compiled Java, just can't match.

Java is a good choice for a program that is meant to be easily deployed across several different platforms.

Although C++ has it's "ease of use" features, it unfortunately also has an incredible complexity as you get deeper into it.

[loornlee]

Hello everyone

im reading this c++ tutorial, now im doing the #4 of the first assignment, manipulating strings.

but i cant get my program to work properly...

this is my code so far

Code:

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    int i, j, n;
    char frase[100]=" ", a[10][10]={' ',' ',' ',' ',' ',' ',' ',' ',' ',' '};
    cout <<"\n\n\nmax 100 characters and 10 words:\n\n";
    gets(frase);
    cout <<"\n";
    for (i=0;i<10;i++)
    {
            for (j=0;j<10;j++)
            {
                n=i*10+j;
                if (frase[n]==' ')
                {
                                break;
                }
                a[i][j]=frase[n];       
            }
    }
    for (i=0;i<10;i++)
    {
        cout<<"\n"<<a[i];
    }
    system("PAUSE");
    return EXIT_SUCCESS;
}

cant realize whats wrong whit it >.<

i was hoping someone can point me in the right direction...

thx in advance ^^

[Midnight Dream]

Originally Posted by loornlee

Hello everyone

im reading this c++ tutorial, now im doing the #4 of the first assignment, manipulating strings.

but i cant get my program to work properly...

this is my code so far

Code:

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    int i, j, n;
    char frase[100]=" ", a[10][10]={' ',' ',' ',' ',' ',' ',' ',' ',' ',' '};
    cout <<"\n\n\nmax 100 characters and 10 words:\n\n";
    gets(frase);
    cout <<"\n";
    for (i=0;i<10;i++)
    {
            for (j=0;j<10;j++)
            {
                n=i*10+j;
                if (frase[n]==' ')
                {
                                break;
                }
                a[i][j]=frase[n];       
            }
    }
    for (i=0;i<10;i++)
    {
        cout<<"\n"<<a[i];
    }
    system("PAUSE");
    return EXIT_SUCCESS;
}

cant realize whats wrong whit it >.<

i was hoping someone can point me in the right direction...

thx in advance ^^

Well, some error output would be helpful, but just so you know, the proper way to return "EXIT_SUCCESS" is to simply do "return 0;" 0 implies success, anything else implies otherwise.

[YellowDart]

My first guess would be your return value. I don't see anywhere in your code where you define EXIT_SUCCESS. Your main method is typed as int, so it's expecting you to return an int.

You might want to just try returning 0 and see if that fixes your error.

[loornlee]

well that part of the code is done by default in Dev-C++ 4.9.9.2 and it works in everything else i've done, anyways i tried changeing that to 0, but still doesnt works =(

[technoViking]

Is the issue you can't compile it or output is wrong (aka you did somthing wrong in the logic)?

I just compiled and ran it fine, of course the output doesn't look right but it compiles.

1>------ Build started: Project: C program, Configuration: Debug Win32 ------
1>Compiling...
1>test.cpp
1>.\test.cpp(11) : warning C4996: 'gets' was declared deprecated
1> C:\Program Files\Microsoft Visual Studio 8\VC\include\stdio.h(270) : see declaration of 'gets'
1> Message: 'This function or variable may be unsafe. Consider using gets_s instead. To disable deprecation, use _CRT_SECURE_NO_DEPRECATE. See online help for details.'
1>Linking...
1>Embedding manifest...
1>Build log was saved at "file://c:\Documents and Settings\Mr. Coffee\My Documents\Visual Studio 2005\Projects\C program\C program\Debug\BuildLog.htm"
1>C program - 0 error(s), 1 warning(s)
========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

Also you might think about using a more up to date tutorial, as you can see its using things that are deprecated ex: gets.

[loornlee]

yeap it compiles, but the output its all wrong =P

do you know some good updated tutorial? =D

thx for the help ^^

[technoViking]

I thought you could add this to the list of C++ tutorials, I wrote this when I was 16 hah, I googled my name, Cory Sanchez and it came up!


http://library.thinkquest.org/C0111571/

[loornlee]

ty! ill check it out, hope i can get my problem solved ^^

[ShadowPho]

Originally Posted by technoViking

Is the issue you can't compile it or output is wrong (aka you did somthing wrong in the logic)?

I just compiled and ran it fine, of course the output doesn't look right but it compiles.



Also you might think about using a more up to date tutorial, as you can see its using things that are deprecated ex: gets.

gets is deprecated?

[technoViking]

Originally Posted by ShadowPho

gets is deprecated?

Yes.

[SauronofMordor]

Good to see you've posted my notes, as they existed in '03. Some things are a little out of date already. Sorry to see you only posted the first two weeks! You should post the rest - advanced functions, pointers, the OOP stuff, java. That's when it gets interesting.

Have you earned your Fields medal yet?

[technoViking]

Did Frodo baggins steal your stuff?

[iaacp]

Hi guys, very late to the party, and this looked like an okay thread to ask. I just now started C++ and am trying to do my own hello world program. I am using Dev-C++. So, I compile with no errors, and as it runs it, the box that I believe would have the "hello world" in it shows up but instantly closes before I can read it.

Can anyone help a mega noob here?

This is what I have:

#include <iostream>

int main()
{
std::cout << "Hello World!\n";
return 0;
}

Edit:If I try to just "Run" the file instead of compile and run, I get the "source file not compiled error". Not sure if that is helpful or not