What's the #if and #endif stand for?

[abhiiyer102]

Hi:
I dont really understand that #if and #endif stand for, for example:
int main(int argc,char *argv[])
{
char abc[20] = "";
int r;
int b;
int c = 3;
char bce[20] = "a";
r = sscanf(&abc[0],"%s",abc);
b = sscanf(&bce[0],"%s",bce);
printf("%s\n",abc);
printf("%d\n",r);
if(r == -1 && b == 1 ){
#if 3
printf("error\n");
#endif
printf("OK\n");
}
printf("OKKKKKKK\n");
return 0;
}
In here, the 3 is stand by the sscanf value? or something else?
Thank you for your help

[Bazzy]

lines starting with # are for the preprocessor; #if,#else,#elif,#ifdef,#ifndef,#endif are used to choose whether compiling or not something. 3 is a constant (always true)

http://www.cplusplus.com/doc/tutorial/preprocessor/