快速的输入输出功能

#define getcx getchar_unlocked
inline void inp( int &n )//fast input function
{
   n=0;
   int ch=getcx();int sign=1;
   while( ch < '0' || ch > '9' ){if(ch=='-')sign=-1; ch=getcx();}

   while(  ch >= '0' && ch <= '9' )
           n = (n<<3)+(n<<1) + ch-'0', ch=getcx();
   n=n*sign;
}

您好我一直在使用输入上述功能在不同的编码比赛，但为什么它快速始终无法理解。我所知道的逻辑，但不知道它的牢度的概念。例如这是什么线做getchar_unlocked的#define getcx。此外，我不知道任何快速输出功能，因此没有任何快速输出功能还可

Hi I have been using the above function for input in various coding contests but was never able to understand why is it fast. I know the logic but don't know the concept of it's fastness. For example what is this line doing "#define getcx getchar_unlocked" . Also I don't know any fast output function so is there any fast output function also