& bitwise help

i learning sprite kit , dealing collisions of objects. got snippet of code apple docs , trying figure out &bitwise operator doing. first time using bitwise. know && logic operator evaluates left , right side true or false.

checking left , right make sure both not equal 0?

code:

  static const uint32_t landercatagory = 0x1;  static const uint32_t rockcatagory = 0x1 << 1;  static const uint32_t photoncatagory = 0x1 << 2;  static const uint32_t edgecatagory = 0x1 << 3;    -(void)didbegincontact:(skphysicscontact *)contact{      skphysicsbody *firstbody;      skphysicsbody *secondbody;            if (firstbody.categorybitmask < secondbody.categorybitmask) {          firstbody = contact.bodya;          secondbody = contact.bodyb;      }      else{          firstbody = contact.bodyb;          secondbody = contact.bodya;      }      [b]      if ((firstbody.categorybitmask & photoncatagory) != 0) [/b]{          nslog(@"big bada boom");      }            nslog(@"contact");  }    

 

it bitwise , operation.

0 , 0 = 0
0 , 1 = 0
1 , 0 = 0
1 , 1 = 1

 

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