Rough guide to the syntax

Main programming elements

• main()

  C++ programs have a main method, outside of every class. This main method will be entered first in the executable and steers all the rest of the program, In most cases this happens via instantiation/initialization of classes and related methods. This method will look like:
  

  int main() {    body of main ;    more body of main; }

  We can already see a couple of things here:
  • Methods have a type identifier - in this case integer.
  • Methods have arguments to be passed in round brackets. In case there are no arguments, the brackets remain empty.
  • The body of a method comes in curly brackets, whci have to be closed.
  • Commands are usually separated by a semicolon.
  • Note that main is a reserved keyword here linked to a specific meaning and note that you need to have a main method.
  
  

• Declaration of classes

  Within C++ programs, major building blocks are classes. Their declaration is done with the keyword class. A simple class declaration would look like:
  

  class myclass { private:     private data;     more private data;     maybe some private method; public:     public data;     constructors;     maybe some public methods; };

  Usually such class declarations will be done in so-called include-files with suffix .H or .h whereas the methods will be filled in files with suffices like .c, .C, or .cpp.
  • We can read off two more keywords here, namely public and private. They define, what can be seen and accessed from outside the class. Let's for instance assume that we have defined a class "vector". You might want to declare the individual vector components as private. This will boil down to the feature that you cannot read or set these components within the main program. In turn, if you declared them as public you would be allowed to do so.
  • Furthermore we see that both methods and data can be public or private.

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