Answer
Four is the number of different bit patterns that can be formed using 2 bits. If more privilege levels were required, the designers would need at least 3 bits to represent the different levels and would therefore probably choose to use a total of 8 levels. In the same manner, the natural choice for fewer than 4 privilege levels would be 2, which is the number of patterns that can be represented with 1 bit.
Work Step by Step
Four is the number of different bit patterns that can be formed using 2 bits. If more privilege levels were required, the designers would need at least 3 bits to represent the different levels and would therefore probably choose to use a total of 8 levels. In the same manner, the natural choice for fewer than 4 privilege levels would be 2, which is the number of patterns that can be represented with 1 bit.
