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these figures. Both DO...WHILE and REPEAT...UNTIL are used for looping. In case of
DO...WHILE, the looping will continue as long as the condition is true. The looping
stops when the condition is not true. On the other hand, in case of REPEAT... UNITL, the
looping continues until the condition becomes true. That is, the execution of the
statements within the loop is repeated as long as the condition is not true.
Notice that in case of DO... WHILE, the condition for looping is checked at the
beginning of the loop. Hence if the condition is found to be false when the loop is first
encountered, the processes in the loop will not be executed at all (not even once). On the
other hand, in case of REPEAT... UNTIL, the condition for looping is checked at the end
of the loop. Hence the processes inside the loop will be executed at least once.
In both the DO...WHILE and REPEAT...UNITL, the loop must contain a statement that
will change the condition that controls the loop. If it does not, the looping will continue
without end, which is the case of an infinite loop. Remember that no program should
contain an infinite loop. Also note that the condition is tested at the top of the loop in the
DO...WHILE and at the bottom of the loop in the REPEAT... UNTIL. ENDDO marks the
end of a DO...WHILE structure and UNTIL followed by some condition marks the end of
the REPEAT...UNTIL structure.
(a) Flow chart
DO WHILE Condition
Figure 11.18. Flowchart and pseudocode for DO...WHILE iteration structure.
The pseudocode version of the logic of the problem of Example 11.6 that was charted in
Figure 11.9 is shown in Figure 11.20. In the pseudocode example, the first line initializes
the value of Count to zero and the second line reads the input data of the first student.
The third line is the beginning of a loop using the DO.. .WHILE structure. It indicates
that the loop will continue so long as the trailer Sexc...
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This document was uploaded on 04/07/2014.
- Spring '14