Programming Forums > Application Development > C++

emdiesse · Oct 25th, 2005, 6:55 AM

Hello there.

I have purchased the book: SAMS Teach Yourself C++ in 21 Days, after my hate towards purchasing the C++ book for dummies (HEAP OF TRIPE)

I have gotten through Lesson 1 (first day) so far and i have a few questions i would like to ask to help me understand it better.

This is the first program you write (obviously):

(Toggle Plain Text)

#include <iostream>                                  //what does this do? I'm guessing the book will explain this later one, but i want to know now! lol Unless if it is best not to yet?

int main()                                           //As previous comment
{                                                    
     std::cout << "Hello World!\n";                  //Whats the benifit of using std:: instead of declaring "using namespace std;"
     system ("PAUSE");                               //I had to add this so that I coukld see the output.
     return 0;                                       //what does this do?
}

My questions are in the comments

Also have question on this

(Toggle Plain Text)

#include <iostream>

int main()
{     
     int x = 5;
     int y = 7;
     std::cout << endl;                                               \\ dev C++ came up with an error with this and std::cout << end; so i removed them, what are they for?
     std::cout << x + y << " " << x * y;
     std::cout << end;                                                 \\ dev C++ came up with an error with this and std::cout << end; so i removed them, what are they for?
     system ("PAUSE");
     return 0;
}

Also, is my purchase of this book a good choice? (I understand it won't make me an advanced C++ programmer, but it will get me started says its aimed at levels begginer to intermediate, so i should be intermediate after, with lots of practice)

Klarre · Oct 25th, 2005, 7:18 AM

Quote:

Originally Posted by emdiesse

std::cout << endl;

try

(Toggle Plain Text)

std::cout << std::endl;

instead.
std::endl = new line. Same as the escape sequence \n, if you have seen that one.

emdiesse · Oct 25th, 2005, 7:52 AM

Quote:

Originally Posted by Klarre

try

(Toggle Plain Text)

std::cout << std::endl;

instead.
std::endl = new line. Same as the escape sequence \n, if you have seen that one.

Thanks, i guessed it was the same as \n

peace_of_mind · Oct 25th, 2005, 8:04 AM

It appears that you really should read a bit more of the book. I have that book, just haven't read it yet, so I can't comment on how good it is. But if #include isn't explained within the first chapter or two you may want to consider another book. Your first two questioned lines should be covered quite well in the early chapters of the book.

pal · Oct 25th, 2005, 8:20 AM

Yes, read more of the book.
Do this

(Toggle Plain Text)

#include <iostream>
using namespace std;

and then get rid of all

(Toggle Plain Text)

std::

I would avoid the ones that says "teach yourself within # days".

DaWei · Oct 25th, 2005, 8:39 AM

Quote:

std::endl = new line. Same as the escape sequence \n, if you have seen that one.

. Not true. "endl" causes the output buffer to be flushed, also.

Instructing the OP to use "using namespace std;" as a matter of course is also incorrect. The desirability of doing that is entirely circumstantial; relating to the coders use (and degree of use) of his/her own (possibly overlapping) namespaces. In simple, short programs, it's usually to be preferred, but it shouldn't be presented as a "do this instead of that."

pal · Oct 25th, 2005, 9:07 AM

My mistake if it sounded like a rant.
I meant to say it as a recommendation.

grumpy · Oct 25th, 2005, 9:46 AM

Others have answered some of the questions. I'll answer some more;

#include <iostream> is a preprocessor directive, which literally pastes the contents of something (commonly called a header file, as it might actually be a text file containing declarations and definitions that are valid C++) named iostream in place of the #include directive. The thing called iostream is a standard header, described in the C++ standard, that allows use of basic stream I/O functionality. For example, std::cout is an output stream, corresponding to a device known as "standard output" that is declared in <iostream>.

int main() is an entry point to a program. When any program starts up, it is necessary to have some way of reaching code that the programmer wants executed. main() is referred to an an entry point and is (typically) the first function under programmer control to be called. There are three forms of main() that all C and C++ compilers must support: int main() -- which takes no arguments is one of them. All required forms of main() return int (which is normally interpreted by your operating environment as an error code).

The benefit of using "std::cout" instead of "using namespace std;" and simplifying it to "cout" is one of avoiding ambiguity (which typically causes a compiler to choke and refuse to compile a program). The std:: prefix means that the object named cout exists in a namespace (literally a universe of names) named std. It is possible to have an object named cout exist in another namespace, in which case using directives can result in ambiguity. In your example, it makes little difference. But here is an example where it does;

(Toggle Plain Text)

#include <iostream>
namespace X
{
    int cout;
}
using namespace std;
using namespace X;

int main()
{
    cout << "Hello\n";
}

This code will not compile, as the "cout" referred to in main() could refer to either std::cout or X::cout (the combination of using directives means both are equally viable candidates when the compiler sees the name cout). This sort of example is quite common when programmers reuse libraries, and is the main reason why using directives are discouraged in header files or library code (code that you write so other people can use it from their programs).

bl00dninja · Oct 26th, 2005, 5:05 AM

grumpy has explained your issues, and as to whether or not it's a good book, i think it is. it goes from hello world to fairly complex things such as multiple inheritance and polymorphism with good explanations. 21 days is a lie though, the book should probably take you 2-3 months to finish (and understand everything).

ivan · Oct 26th, 2005, 5:20 AM

The time to understand the book depends on your programming experience. If you have not programmed before it will take you longer to understand it good.

Oct 25th, 2005, 6:55 AM	#1
emdiesse Programmer Join Date: Jul 2004 Location: Hampshire Posts: 56 Rep Power: 5	Road to C++ Hello there. I have purchased the book: SAMS Teach Yourself C++ in 21 Days, after my hate towards purchasing the C++ book for dummies (HEAP OF TRIPE) I have gotten through Lesson 1 (first day) so far and i have a few questions i would like to ask to help me understand it better. This is the first program you write (obviously): (Toggle Plain Text) #include <iostream> //what does this do? I'm guessing the book will explain this later one, but i want to know now! lol Unless if it is best not to yet? int main() //As previous comment { std::cout << "Hello World!\n"; //Whats the benifit of using std:: instead of declaring "using namespace std;" system ("PAUSE"); //I had to add this so that I coukld see the output. return 0; //what does this do? } #include <iostream> //what does this do? I'm guessing the book will explain this later one, but i want to know now! lol Unless if it is best not to yet? int main() //As previous comment { std::cout << "Hello World!\n"; //Whats the benifit of using std:: instead of declaring "using namespace std;" system ("PAUSE"); //I had to add this so that I coukld see the output. return 0; //what does this do? } My questions are in the comments Also have question on this (Toggle Plain Text) #include <iostream> int main() { int x = 5; int y = 7; std::cout << endl; \\ dev C++ came up with an error with this and std::cout << end; so i removed them, what are they for? std::cout << x + y << " " << x * y; std::cout << end; \\ dev C++ came up with an error with this and std::cout << end; so i removed them, what are they for? system ("PAUSE"); return 0; } #include <iostream> int main() { int x = 5; int y = 7; std::cout << endl; \\ dev C++ came up with an error with this and std::cout << end; so i removed them, what are they for? std::cout << x + y << " " << x * y; std::cout << end; \\ dev C++ came up with an error with this and std::cout << end; so i removed them, what are they for? system ("PAUSE"); return 0; } Also, is my purchase of this book a good choice? (I understand it won't make me an advanced C++ programmer, but it will get me started says its aimed at levels begginer to intermediate, so i should be intermediate after, with lots of practice)

Oct 25th, 2005, 8:04 AM	#4
peace_of_mind Professional Programmer Join Date: Sep 2004 Location: Hell if I know most of the time Posts: 439 Rep Power: 5	It appears that you really should read a bit more of the book. I have that book, just haven't read it yet, so I can't comment on how good it is. But if #include isn't explained within the first chapter or two you may want to consider another book. Your first two questioned lines should be covered quite well in the early chapters of the book. __________________ Amateurs built the ark Professionals built the Titanic

Oct 25th, 2005, 8:20 AM	#5
pal Programmer Join Date: Mar 2005 Location: Washington Posts: 91 Rep Power: 4	Yes, read more of the book. Do this (Toggle Plain Text) #include <iostream> using namespace std; #include <iostream> using namespace std; and then get rid of all (Toggle Plain Text) std:: std:: I would avoid the ones that says "teach yourself within # days".

Oct 25th, 2005, 9:46 AM	#8
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,260 Rep Power: 5	Others have answered some of the questions. I'll answer some more; #include <iostream> is a preprocessor directive, which literally pastes the contents of something (commonly called a header file, as it might actually be a text file containing declarations and definitions that are valid C++) named iostream in place of the #include directive. The thing called iostream is a standard header, described in the C++ standard, that allows use of basic stream I/O functionality. For example, std::cout is an output stream, corresponding to a device known as "standard output" that is declared in <iostream>. int main() is an entry point to a program. When any program starts up, it is necessary to have some way of reaching code that the programmer wants executed. main() is referred to an an entry point and is (typically) the first function under programmer control to be called. There are three forms of main() that all C and C++ compilers must support: int main() -- which takes no arguments is one of them. All required forms of main() return int (which is normally interpreted by your operating environment as an error code). The benefit of using "std::cout" instead of "using namespace std;" and simplifying it to "cout" is one of avoiding ambiguity (which typically causes a compiler to choke and refuse to compile a program). The std:: prefix means that the object named cout exists in a namespace (literally a universe of names) named std. It is possible to have an object named cout exist in another namespace, in which case using directives can result in ambiguity. In your example, it makes little difference. But here is an example where it does; (Toggle Plain Text) #include <iostream> namespace X { int cout; } using namespace std; using namespace X; int main() { cout << "Hello\n"; } #include <iostream> namespace X { int cout; } using namespace std; using namespace X; int main() { cout << "Hello\n"; } This code will not compile, as the "cout" referred to in main() could refer to either std::cout or X::cout (the combination of using directives means both are equally viable candidates when the compiler sees the name cout). This sort of example is quite common when programmers reuse libraries, and is the main reason why using directives are discouraged in header files or library code (code that you write so other people can use it from their programs).

Oct 26th, 2005, 5:05 AM	#9
bl00dninja Programming Guru Join Date: Oct 2004 Location: namespace std Posts: 1,246 Rep Power: 6	grumpy has explained your issues, and as to whether or not it's a good book, i think it is. it goes from hello world to fairly complex things such as multiple inheritance and polymorphism with good explanations. 21 days is a lie though, the book should probably take you 2-3 months to finish (and understand everything). __________________ i put on my robe and wizard hat... Have you ever heard of Plato, Aristotle, Socrates?...Morons.

Oct 25th, 2005, 9:07 AM	#7
pal Programmer Join Date: Mar 2005 Location: Washington Posts: 91 Rep Power: 4	My mistake if it sounded like a rant. I meant to say it as a recommendation.

Oct 26th, 2005, 5:20 AM	#10
ivan Professional Programmer Join Date: Sep 2005 Location: serbia & montenegro Posts: 484 Rep Power: 4	The time to understand the book depends on your programming experience. If you have not programmed before it will take you longer to understand it good.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Programming Forums > Application Development > C++

Road to C++