Bits

Hi /prog/rammers...

I'm an hobby programmer and I'm here to ask a really simple question... I tried to google it but I don't even know where to start my search

the notation:
0x00 = 00000000
how it is called?
how can I convert an 8bit array in this form?
for example how can I discover the notation or the bit pattern?
?? = 00110100
0xff = ??

can someone explain me the logic behind?

thank you...

0-15 = 0 1 2 3 4 5 6 7 8 9 A B C D E F

To convert, take successive blocks of 4 bits from the end of the string (b1, b2, b3, b4) -- the hex value is b4 + b3 * 2 + b2 * 4 + b1 * 8, look this number up in the table above and replace with hex character.