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Cplusplus: Difference between revisions
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opcode only specifies an instruction. Machine code (of which assembly language is a human-readable representation) is accurate.
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''Under construction | '''Under construction.''' | ||
'''C++''' is an object-oriented programming language, developed as a superset of the language C, which means that the language is | ''If you have any problems with this tutorial or want to give feedback, ask questions or get additional help, please e-mail coconut<at>redbrick<dot>dcu<dot>ie or, for general [[Helpdesk]] queries, helpdesk<at>redbrick<dot>dcu<dot>ie. '' | ||
'''C++''' is an object-oriented programming language, developed as a superset of the language [[C]], which means that the language is essentially C with more features, hence the name. However, it has since evolved into a separate language and compatibility with C is no longer guaranteed. | |||
It is a very popular all-purpose language which is commonly utilised for game programming, and in many respects is quite similar to [[Java]], another object-oriented language. | It is a very popular all-purpose language which is commonly utilised for game programming, and in many respects is quite similar to [[Java]], another object-oriented language. | ||
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==g++== | ==g++== | ||
The page [[Programming On Redbrick]] explains how to compile programs written in C++. Here we will go into more depth as to how the compiler g++ works. | The page [[Programming On Redbrick]] explains how to compile programs written in C++. Here we will go into more depth as to how the compiler g++ works. | ||
A compiler works by translating your programming language (in this case, C++) into | A compiler works by translating your programming language (in this case, C++) into machine code, which is the basic language that a processor understands. While C++ is a universal language (source code written on one architecture will generally work on another unless special libraries are used), programs must be recompiled if they are to be used on different architectures - for example, if you are compiling on murphy, which uses the UltraSPARC architecture, you will have to recompile your program if you wish to use it on carbon or deathray, which use the Intel x86 architecture, because UltraSPARC and x86 assembly languages are completely different. | ||
g++ is the free, open-source C++ compiler which is included with many distributions of Linux as part of the gcc package, the latter of which is a C compiler. Other popular C++ compilers include Borland C++ and Microsoft Visual C++, however these are proprietary. gcc (and g++) is the most widely ported and universally available compiler in the world. | g++ is the free, open-source C++ compiler which is included with many distributions of Linux as part of the gcc package, the latter of which is a C compiler. Other popular C++ compilers include Borland C++ and Microsoft Visual C++, however these are proprietary. gcc (and g++) is the most widely ported and universally available compiler in the world. | ||
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mkdir C++ | mkdir C++ | ||
This will create a directory called "C++" in your home directory. | This will create a directory called "C++" in your home directory. Enter this directory by typing | ||
cd C++ | cd C++ | ||
Now you're ready to create your first C++ program. For this tutorial, we are going to use the [[nano]] editor | Now you're ready to create your first C++ program. For this tutorial, we are going to use the [[nano]] editor. Make a new C++ source file, that we will call "first", with | ||
nano first.cpp | nano first.cpp | ||
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using namespace std; | using namespace std; | ||
int main() | int main() | ||
{ | { | ||
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For example, if you want the loop to end early when a certain condition is met, just use an if statement inside the loop and have the loop break if this condition is met. | For example, if you want the loop to end early when a certain condition is met, just use an if statement inside the loop and have the loop break if this condition is met. | ||
==Executing system commands in C++== | |||
It is possible to execute system commands from within your C++ program. If your program is command-line only, you can execute simple commands such as those to clear the screen, etc. | |||
If you're using Linux, the code is | |||
system("clear"); | |||
You can also do this if you're running Windows (although why would you want to?) The DOS clear command is "cls" | |||
system("cls"); | |||
...like so! | |||
However, it is recommended that you '''not''' use system commands in your code for something as trivial as clearing the screen. It's a resource hog and leaves a gaping security hole in your C++ program. There is a better way to do this in C++, however it requires advanced knowledge of the language and is available below under ''Advanced''. | |||
==Functions: The Basics== | |||
It's now time to move on to '''functions'''. A function is basically the same thing as a method in Java: it is a sequence of commands which can be called upon at any time, passed parameters and set to return a value. | |||
main() is a function - the default function for a C++ program. But what if you have some code that you don't want to put into main? Use another function. | |||
Let's say we want to add two numbers together and print out the result. The code could look something like this: | |||
#include <iostream> | |||
using namespace std; | |||
int add(int a, int b) | |||
{ | |||
return a + b; | |||
} | |||
int main() | |||
{ | |||
int a = 2; | |||
int b = 5; | |||
cout << add(a,b) << endl; | |||
return(0); | |||
} | |||
This program adds 2 and 5 together to get 7, and displays this answer on-screen. | |||
a and b are passed as ''parameters'' to the add function - they are then immediately added together and the answer is returned. Experiment with this code to do different things. | |||
==More advanced C++== | |||
I'll get around to this someday. I'm still learning too you know! | |||
[[Category:Helpdesk]] | [[Category:Helpdesk]] | ||