Art of Assembly Language, 1st Edition

11.7. 11.7 Packed Arrays of Bit Strings

Although it is far more efficient to create arrays whose elements have an integral number of bytes, it is quite possible to create arrays of elements whose size is not a multiple of 8 bits. The drawback is that calculating the "address" of an array element and manipulating that array element involves a lot of extra work. In this section we'll take a look at a few examples of packing and unpacking array elements in an array whose elements are an arbitrary number of bits long.

Before proceeding, it's probably worthwhile to discuss why you would want to bother with arrays of bit objects. The answer is simple: space. If an object only consumes 3 bits, you can get 2.67 times as many elements into the same space ...