c++ Machine code MIPS

if i am given 000000 00000........(32 bits) how would I go about getting the first 6 bits only?

int main(){

string code;

cout << "Enter code";

cin << code << endl;

//000000000000...............(32 bits)

for(int i = 0; i < 6; i++){

if all bits are 0 then call R type decode function

elseif bits equal 2 or 3 call Jtype decode instruction

}

}