Page 163 - DCAP507_SYSTEM_SOFTWARE

Unit 10: Programming Languages Concept (I)

Array Initialization Notes

Although it is not possible to assign to all elements of an array at once using an assignment
expression, it is possible to initialize some or all elements of an array when the array is defined.
The syntax looks like this:
int a[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
The list of values, enclosed in braces {}, separated by commas, provides the initial values for
successive elements of the array.
If there are fewer initializers than elements in the array, the remaining elements are automatically
initialized to 0.

Example:
int a[10] = {0, 1, 2, 3, 4, 5, 6};

would initialize a[7], a[8], and a[9] to 0. When an array definition includes an initializer, the
array dimension may be omitted, and the compiler will infer the dimension from the number of
initializers.

Example:

int b[] = {10, 11, 12, 13, 14};
would declare, define, and initialize an array b of 5 elements (i.e. just as if you'd typed int b[5]).
Only the dimension is omitted; the brackets [] remain to indicate that b is in fact an array.

In the case of arrays of char, the initializer may be a string constant:
char s1[7] = "Hello,";
char s2[10] = "there,";

char s3[] = "world!";
As before, if the dimension is omitted, it is inferred from the size of the string initializer. (We
haven't covered strings in detail yet--we'll do so in chapter 8--but it turns out that all strings in
C are terminated by a special character with the value 0. Therefore, the array s3 will be of size 7,
and the explicitly-sized s1 does need to be of size at least 7. For s2, the last 4 characters in the
array will all end up being this zero-value character.)

Arrays of Arrays ("Multidimensional" Arrays)

When we said that "Arrays are not limited to type int; you can have arrays of... any other type,"
we meant that more literally than you might have guessed. If you have an "array of int," it means
that you have an array each of whose elements is of type int. But you can have an array each of
whose elements is of type x, where x is any type you choose. In particular, you can have an array
each of whose elements is another array! We can use these arrays of arrays for the same sorts of
tasks as we'd use multidimensional arrays in other computer languages (or matrices in
mathematics). Naturally, we are not limited to arrays of arrays, either; we could have an array
of arrays of arrays, which would act like a 3-dimensional array, etc.
The declaration of an array of arrays looks like this:

int a2[5][7];

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