Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 8 ■ Arrays
Now, suppose score is declared in main as
int score[10];
and we make the call
sumList(score);
We can simply think that, in the function, score is known by the name num; any reference to
num is a reference to the original argument score.
The more precise explanation is this: since the name score denotes the address of score[0],
this address is passed to the function where it becomes the address of the first element of num,
num[0]. In fact, any address can be passed to the function where it will be taken to be the address
of num[0].
The function is free to assume any size it wishes for num. Obviously, this could land us in
trouble if we attempt to process array elements that do not exist. For this reason, it is good
programming practice to ‘tell’ the function how many elements to process. We do this using
another argument, as in:
int sumList(int num[], int n)
Now the calling function can tell sumList how many elements to process by supplying a value
for n. Using the declaration of score, above, the call
sumList(score, 10);
tells the function to process the first 10 elements of score (the whole array). But, and herein lies
the advantage of this approach: we could also make a call such as
sumList(score, 5);
to get the function to process the first 5 elements of score.
Using this function header, we write sumList as follows:
int sumList(int num[], int n) {
int sum = 0;
for (int h = 0; h < n; h++) sum += num[h];
return sum;
}
The function ‘steps through’ the array, from num[0] to num[n-1], using a for loop. Each time
through the loop, it adds one element to sum. On exit from the loop, the value of sum is returned as
the value of the function.
The construct
for (h = 0; h < n; h++)
is typical for processing the first n elements of an array.
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