What are bitfields?

[deathemperor]

let me try to explain.

like the above example:

32
16
8
4
2
1

this is 65, in your database you have a field called permissionwhatever to store that number (65), and if a usergroup has that value 65 it means they have full permission, each bit represent for a permission. if it's 64, then the value you don't have must be 1, 60 means without 1 and 4 and it cannot be any other number. so that's the way it realizes you don't have what permission.

[akanevsky]

Well ... all Powers of 2 except 2^0 are even.
So if a number is odd, it must have Bit 0 (2^0=1) set, so this functions checks for this Bit being set.

I don't understand the connection between 0 power and Bit 0? =//

1*2^0 = 1*1 = 1
0*2^1 = 0*2 = 0
1*2^2 = 1*4 = 4
In Total: 5

How do you convert decimals to binarys?

let me try to explain.

like the above example:

32
16
8
4
2
1

this is 65, in your database you have a field called permissionwhatever to store that number (65), and if a usergroup has that value 65 it means they have full permission, each bit represent for a permission. if it's 64, then the value you don't have must be 1, 60 means without 1 and 4 and it cannot be any other number. so that's the way it realizes you don't have what permission.

I understand this, thanks...

[Marco van Herwaarden]

Also have a look at this post: https://vborg.vbsupport.ru/showpost....62&postcount=4

Might help in understanding

[akanevsky]

Okay, I already completely understand how the vB permissions work

What I do not understand is this:

Originally Posted by Dark Visor

I don't understand the connection between 0 power and Bit 0? =//

[Andreas]

Hmm, what exactly do you not understand?
2^0 = 1
2^1 = 2
2^2 = 4
2^3 = 8
2^4 = 16
...
As you can see, all numbers are even - except 1. So if you add them together, you will always get an even number if 1 is not included.
1 is 2^0, which means this bit must be set if a number is odd.

[akanevsky]

Oh!!! Yeah, now I understand.
When a number is an even number, it consists of such sub-numbers, as 2,4,8,16, but not 1. And when a number is odd, it has 1 included, so 3 & 1 works This is so cool...

Thanks everyone.