Chapter 3.3, Problem 5QE

Explanation of Solution

Fraction of the machine’s time that is spent actually to perform processes:

• If each time slice in a multiprogramming system is $50\text{ milliseconds}=\left(50\times {10}^{-3}\text{s}\right)$, then  each context switch requires at most a microsecond $\left({10}^{-6}\text{s}\right)$.
• The fraction of the machine’s time is spent actually performing processes is the ratio of the time slice and the sum of a time slice and time required by context switch,

$\begin{array}{c}\text{Fraction}=\frac{50\times {10}^{-3}\text{s}}{\left(50\times {10}^{-3}\text{s}\right)+{10}^{-6}\text{s}}\\ =\frac{5000\times {10}^{-6}\text{s}}{(5000}\end{array}$