Programming in C

102 Chapter 7 Working with Arrays

Bad response: 15

5

5

1

7

4

10

5

5

6

8

9

Rating Number of Responses

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1 1

2 0

3 1

4 1

5 6

6 3

7 2

8 2

9 2

10 1

The arrayratingCountersis defined to contain 11 elements. A valid question you

might ask is, “If there are only 10 possible responses to the survey, why is the array

defined to contain 11 elements rather than 10?”The answer lies in the strategy for

counting the responses in each particular rating category. Because each response can be a

number from 1 to 10, the program keeps track of the responses for any one particular

rating by simply incrementing the corresponding array element (after first checking to

make certain that the user entered a valid response between 1 and 10). For example, if a

rating of 5 is typed in, the value of ratingCounters[5]is incremented by one. By

employing this technique, the total number of respondents who rated the TV show a 5

are contained in ratingCounters[5].

The reason for 11 elements versus 10 should now be clear. Because the highest rating

number is a 10, you must set up your array to contain 11 elements to index

ratingCounters[10],remembering that because of the zeroth element, the number of

elements in an array is always one more than the highest index number. Because no

response can have a value of zero,ratingCounters[0]is never used. In fact, in the for

loops that initialize and display the contents of the array, note that the variable istarts at

1 , and thereby bypasses the initialization and display of ratingCounters[0].

Program 7.2 Continued