[RESOLVED] Bits, Bytes and Boomerangs (without the boomerangs...)

[szlamany]

So one thing I am still a bit puzzled about (it may just be the terminology) is bit shifting. If I can test for any individual bit being set by just using AND then why/when would I use bit shifting? Is that more for when you want to set a bit rather than just checking to see if a bit is set?

That OPCODE is 4 bits - right? That means it's a value from 0000 (0) to 1111 (15).

If you want to extract that value - and it's in the BYTE - you need to shift it down to position 0 and also MASK it to hide other bits that shift down with it.

So once again - the byte with the opcode - let's say it:

1101 0111

The 1010 bits is the 10 values I want to extract. The decimal value of 1101 0111 is not 10 [edit - oops] - so first thing is to shift it down

1101 0111 / 8

0001 1010 - now the 1010 is in bit 0, bit 1, bit 2 and bit 3
0000 1111 - this is the 15 mask

AND these and you get

0000 1010 - this is the 10 I want - it's in a byte - but the value of 10 (from the opcode) came through.