a[0] |= b
is basically
a[0] = a[0] | b
“|” is an or bitwise operator
Update
When a[0] is assigned 0, a[0] in binary is 0000. In the loop,
-
b = 0
a[0] = 0 (base 10) = 0000 (base 2) b = 0 (base 10) = 0000 (base 2) --------------- a[0] | b = 0000 (base 2) = 0 (base 10) -
b = 1
a[0] = 0 (base 10) = 0000 (base 2) b = 1 (base 10) = 0001 (base 2) --------------- a[0] | b = 0001 (base 2) = 1 (base 10) -
b = 2
a[0] = 1 (base 10) = 0001 (base 2) b = 2 (base 10) = 0010 (base 2) --------------- a[0] | b = 0011 (base 2) = 3 (base 10) -
b = 3
a[0] = 3 (base 10) = 0011 (base 2) b = 3 (base 10) = 0011 (base 2) --------------- a[0] | b = 0011 (base 2) = 3 (base 10) -
b = 4
a[0] = 3 (base 10) = 0011 (base 2) b = 4 (base 10) = 0100 (base 2) --------------- a[0] | b = 0111 (base 2) = 7 (base 10) -
b = 5
a[0] = 7 (base 10) = 0111 (base 2) b = 5 (base 10) = 0101 (base 2) --------------- a[0] | b = 0111 (base 2) = 7 (base 10) -
b = 6
a[0] = 7 (base 10) = 0111 (base 2) b = 6 (base 10) = 0110 (base 2) --------------- a[0] | b = 0111 (base 2) = 7 (base 10) -
b = 7
a[0] = 7 (base 10) = 0111 (base 2) b = 7 (base 10) = 0111 (base 2) --------------- a[0] | b = 0111 (base 2) = 7 (base 10) -
b = 8
a[0] = 7 (base 10) = 0111 (base 2) b = 8 (base 10) = 1000 (base 2) --------------- a[0] | b = 1111 (base 2) = 15 (base 10) -
b = 9
a[0] = 15 (base 10) = 1111 (base 2) b = 9 (base 10) = 1001 (base 2) --------------- a[0] | b = 1111 (base 2) = 15 (base 10)
At the end of the loop the value of a[0] is 15