Page 20 - demo

Uniprogramming

Program A Run Wait Run Wait

Time

(a) Uniprogramming

 The processor spends a certain amount of

time executing, until it reaches an I/O

Run
Wait
Run
Wait
Program A instruction; it must then wait until that I/O
instruction concludes before proceeding

Program B Wait Run Wait Run Wait

Run Run Run Run
Combined Wait Wait
A B A B

Time

(b) Multiprogramming with two programs

Program A Run Wait Run Wait

Program B Wait Run Wait Run Wait

Program C Wait Run Wait Run Wait

Run Run Run Run Run Run
Combined Wait Wait
A B C A B C

Time

(c) Multiprogramming with three programs

Figure 2.5 Multiprogramming Example