Art of Assembly Language, 1st Edition

2.12. 2.12 Bit Fields and Packed Data

Although the 80×86 operates most efficiently on byte, word, and double word data types, occasionally you'll need to work with a data type that uses some number of bits other than 8, 16, or 32. For example, consider a date of the form "04/02/01." It takes three numeric values to represent this date: a month, day, and year value. Months, of course, take on the values 1..12. It will require at least 4 bits (maximum of 16 different values) to represent the month. Days range between 1..31. So it will take 5 bits (maximum of 32 different values) to represent the day entry. The year value, assuming that we're working with values in the range 0..99, requires 7 bits (that can be used to represent up to 128 different ...