Sams Teach Yourself C++ in 21 Days

You declare an array by writing the type, followed by the array name and the subscript.

The subscript is the number of elements in the array, surrounded by square brackets. For

example,

long LongArray[25];

declares an array of 25 longintegers, named LongArray. When the compiler sees this

declaration, it sets aside enough memory to hold all 25 elements. If each longinteger

requires four bytes, this declaration sets aside 100 contiguous bytes of memory, as illus-

trated in Figure 13.1.

408 Day 13

FIGURE13.1

Declaring an array.

4 bytes

100 bytes

Accessing Array Elements..............................................................................

You access an array element by referring to its offset from the beginning of the array.

Array element offsets are counted from zero. Therefore, the first array element is referred

to as arrayName[0]. In the LongArrayexample,LongArray[0]is the first array element,

LongArray[1]the second, and so forth.

This can be somewhat confusing. The array SomeArray[3]has three elements. They are

SomeArray[0],SomeArray[1], and SomeArray[2]. More generally,SomeArray[n]has n

elements that are numbered SomeArray[0]through SomeArray[n-1]. Again, remember

that this is because the index is an offset, so the first array element is 0 storage locations

from the beginning of the array, the second is 1 storage location, and so on.

Therefore,LongArray[25]is numbered from LongArray[0]through LongArray[24].

Listing 13.1 shows how to declare an array of five integers and fill each with a value.

Starting with today’s listings, the line numbers will start with zero. This is to

help you remember that arrays in C++ start from zero!

NOTE