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My question is on  the following testing  C code in test.c

Question-1
keyword of __cpluscplus is stand for the file extension of the running file such as test.c, Right ?
so  test.c file has  c file extension so the following typedef will be active, right ?
#ifndef __cplusplus
typedef unsigned char bool;
static const bool False = 1;
static const bool True = 0;
#endif

Question-2  What is different between defined the function as macro  and define function in the code body ?Any advantage over others ? Both I tested to get the same result.
#define getmax_macro(a,b) ((a)>(b)?(a):(b))
int getmax(int a, int b){}

Please advise

Rwniceing

test.c
======

#include <stdio.h>#ifndef __cplusplustypedef unsigned char bool;static const bool False = 1;static const bool True = 0;#endif#define getmax_macro(a,b) ((a)>(b)?(a):(b))int getmax(int a, int b){ if (a>b)return a;else return b;}int main(){    #if !defined(__BOOL_DEFINED)        printf("bool is not supported");    #elif defined(__BOOL_DEFINED)    printf("bool is supported%d",__BOOL_DEFINED);    #endif	bool arr[2] = {false, true};	printf("bool is supported%d",arr[0]);    int x=5, y;    y= getmax_macro(x,2);    printf("getmax_macro: %d",y);    y= getmax(x,2);    printf("getmax: %d",y);    return 0;}                                  

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Yes, macros are expanded in a pre-compile step by the preprocessor (http://en.wikipedia.org/wiki/Preprocessor)

When to put functionality into a function or to a macro depends on the need (and a bit on the habit of the programmer).

Macros IMO have some disadvatages compared to functions, i.e.:
- they (at least with IDEs/debuggers I know) cannot be debugged
- it's not possible to overload functions (see http://www.learncpp.com/cpp-tutorial/76-function-overloading/)
- parameters have no type, so i.e. it's not possible to write a SWAP macro
- with functions the compiler can decide whether it's better to use it inlined or not, macros are always inlined and therefor may blow up the code without any benefit.

I for myself in case both macro or function is possible for a needed functionality prefer functions. In a case like your 'getmax' sample this is not the best solution since in this case I would have to implement the same function multiple times for any variable type (i.e. once for int, once for float). In this case I prefer using a function template instead of a macro because types are defined (i.e. with your macro you can compare an int with a float, in a function template you can avoid or allow using different types).

So I would implement such a getmax-functionality as a template somehow like this:

template < typename _TYPE >_TYPE GetMax( _TYPE a, _TYPE b ){  return ( a > b ? a : b );}                                          

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#define SIZEOF_ARRAY( x ) ( sizeof( x ) / sizeof( x[0] ) )double numbers[] = { 1.0, 1.5, 1.8, 2.3, 2.7 };for ( int n = 0; n < SIZEOF_ARRAY( numbers ); n++ ){ cout << numbers[n];}                                          

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