I'm trying to understand the following code.

What this code is trying to do is return 1 if 0x30 <= x <= 0x39 otherwise it returns 0.

How is the following code accomplishing the above? I want to understand how the code is checking whether x is between 0x30 and 0x39 using the code below.

int isAsciiDigit(int x) {

int a = x<<6;

int b = x<<5;

int c = x<<4;

int d = x<<3;

int e = x<<2;

int f = x<<1;

return (!(a))&((b)) & (c) & (~(d) | (~(e) & ~(f)));

}