Cheat Engine

h3x1c

I ran across an interesting value in a game that uses the 1 bits from a nibble to indicate an item!

For example, 1111 would show 4 of an item on the screen, where 0011 would show 2. Consequently, 1001 also shows 2, as does 1010, 0101, and so forth, the same being the case for any number displayed on the screen from 1-4 based on any given nibble.

With that said, the game never writes bits like that because of the control flow of the bitwise instructions (in other words, you'll always have the nibble look like this as you gain items: 0001 for 1, 0011 for 2, 0111 for 3, 1111 for 4).

So, each byte at a max value of FF equals 8 items. Kind of interesting and I've never seen it before. Bit masking is what I think it falls under, but I didn't know if there was something else to describe this particular scenario. Thanks!

Zanzer · Posted: Wed Aug 03, 2016 6:48 pm Post subject:

Process of using bit masking to compress 8 logic true/false flags into a single byte.
/shrug

ulysse31 · Posted: Wed Aug 03, 2016 7:32 pm Post subject:

It's often used in memory scanners as bit masking is an effective way to save results (ie variables that passed all scans) within a memory block.

++METHOS · Posted: Wed Aug 03, 2016 8:04 pm Post subject:

They're also called boolean values (1 for true, 0 for false). Very Happy

Dark Byte · Posted: Thu Aug 04, 2016 3:15 am Post subject:

could also be a set

e. g pascal (omg who uses that?) tends to store sets into a single byte if possible

Zanzer · Posted: Thu Aug 04, 2016 6:05 am Post subject:

A set is an easier way to visual what's going on. His set is:

h3x1c · Posted: Thu Aug 04, 2016 9:01 am Post subject:

Great feedback from all of you with this. Thank you!

I've been trying to research outdated/alternate methods of storing information after running across this. Just ran into packed-decimal format and have been reading through this wonderful explanation of it.

Have any of you ran into games with values stored like that yet?

Zanzer · Posted: Thu Aug 04, 2016 10:26 am Post subject:

Nope. Not likely to see this in a game, because they're not coded in COBOL or for the mainframe. Smile

Don't waste too many brain cells on that.

mgr.inz.Player · Posted: Thu Aug 04, 2016 4:44 pm Post subject:

Metro: Last Light also uses this data type for number of syringes.

"Population count" ("Hamming weight") - 5 set bits means 5, 4 set bits (doesn't matter which one) means 4, and so on.

I also wrote custom type some time ago:
http://forum.cheatengine.org/viewtopic.php?t=565981

PS: this custom type can be used to find some game Boolean variables.