Hello everyone,
I'm not new to programming in C++, i just bought a new book, a "software eingeering" one. and he's covering some things i must have skipped along the ways of reading bad online tutorials,



okay anyways here is the code

Code:
#define MT
    #ifdef MT
    #define NFILE 40
    #else
    #define NFILE 20
#end if
alright so called explanation which i don't get really:
This code is similiar to what you find in the header files; if hte symbol MT is defined, the limit for the number of files is 40; if we remove its definition form the source file, the lmit will be 20.

now what does it mean "if the symbol MT is defined" ?
can u give me an example when number one will be true? the number of files == 40, and one of the examples when the number of files == 20? or make up your own example that is eaiseer to understand
also i don't understand
Code:
#ifdef CPLUSPLUS
//whatever is needed when the program is wirtten in C++
#endif
or
Code:
#define __cplusplus
   #ifdef __cplusplus
//whatever is needed when the program is written in C++
#end if
can u give me an code example that makes those statements run.

I understand how a simple one works like this:

Code:
#include <iostream>
#include <cmath>
#define Pi 3.1415926
using namespace std;


int main()
{
	double x,y = 1;
	double result;

	cout <<"Welcome to the vb-world.com!" << endl;
	x = y + 1;
	result = pow(Pi,x);
	cout <<"In that world, pi square is: " << result << endl;
	cout <<"Have a nice day!" << endl;
return 0;
}


thansk for your time!!