Explain Faster I/O Method

Im Also Interested to Use Faster I/O methos in my programme.When I had gone through some solutions I have seen this code snippet in most of them used for fast input and fast output

Can Anyone explain me these functions clearly and how they are improving our running time??

inline void fastRead(int *a)
{
register char c=0;
while (c<33) c=getchar_unlocked();
*a=0;
while (c>33)
{
*a=*a*10+c-'0';
c=getchar_unlocked();
}
}
inline void fastWrite(int a)
{
register char c;
char snum[20];
int i=0;
do
{
snum[i++]=a%10+48;
a=a/10;
}while(a!=0);
i=i-1;
while(i>=0)
putchar_unlocked(snum[i--]);
putchar_unlocked('\n');
}