Unique ID (Might be Binary or something) - identifier

Question

// Okay originally people do their IDs for stuff like this:
var Item1 = 0;
var Item2 = 1;
var Item3 = 2;
var Item4 = 3;
var Item5 = 4;
// ... and so on.
// Then create more variables for their checks like:
var HasItem1 = false;
var HasItem2 = false;
var HasItem3 = false;
var HasItem4 = false;
var HasItem5 = false;
// Then somewhere in their code set the items to true if they want the user or player to // have the item, but that's alot of variables.
// Instead I wanted to do something like this:
var Item1 = 1;
var Item2 = 2;
var Item3 = 4;
var Item4 = 8;
var Item5 = 16;
var HasItems = 0; // 0 = no items added.
// The somewhere in my code:
HasItems = Item1 + Item3 + Item4; // 1 + 4 + 8 = 13
// But can't find a way to check if the player has Item3 for example.
if(HasItems != 0 && (HasItems & Item3) != -1) { // It was something like this.
// Has the item we're looking for.
}
// Seen the ID system I'm talking about before, I forget where.
// Anyone know about this system of IDs?
// !!!EDIT!!!
http://blog.millermedeiros.com/using-integers-to-store-multiple-boolean-values/
Example:
[code]
var Item1 = (1 << 1);
var Item2 = (1 << 2);
var Item3 = (1 << 3);
var Item4 = (1 << 4);
var Item5 = (1 << 5);
var Items = (Item1 | Item3 | Item4);
if(Items & Item1) {
print("true 1");
}
else {
print("false 1");
}
if(Items & Item2) {
print("true 2");
}
else {
print("false 2");
}
if(Items & Item3) {
print("true 3");
}
else {
print("false 3");
}
if(Items & Item4) {
print("true 4");
}
else {
print("false 4");
}
if(Items & Item5) {
print("true 5");
}
else {
print("false 5");
}
[/code]
Output:
true 1
false 2
true 3
true 4
false 5
Thank you all for your responses, I searched bitwise and walla.
Special thanks to winterblood!
For your concern, I know it only supports a limited amount of values, this is meant for small systems.

Answer 1

Checking for 1 bit can be done with the following code:
(HasItems & (1 << itemNumber)) != 0
where itemNumber is number of item, starting at 0.
Also, this may be more universal and convenient:
http://msdn.microsoft.com/en-us/library/system.collections.bitarray.aspx
http://msdn.microsoft.com/en-us/library/system.collections.specialized.bitvector32.aspx