Figure 1 shows an algorithm designed to validate booking times at a sports court and calculate the duration of the booking.

Figure 1

1  validBooking ← False
2  REPEAT
3      duration ← -1
4      OUTPUT 'Enter start hour'
5      startHour ← USERINPUT
6      OUTPUT 'Enter end hour'
7      endHour ← USERINPUT
8      IF startHour ≥ endHour THEN
9          OUTPUT 'Start hour must be before end hour'
10     ELSE
11         IF startHour > 12 THEN
12             OUTPUT 'Start hour must be before noon'
13         ELSE
14             validBooking ← True
15         ENDIF
16     ENDIF
17 UNTIL validBooking = True
18 duration ← endHour - startHour
19 OUTPUT duration

Table 1 shows three tests used to check the algorithm in Figure 1.