Quick start manual

Data types, variables, and constants 5-19
Structured types
Arrays
An array represents an indexed collection of elements of the same type (called the
base type). Because each element has a unique index, arrays, unlike sets, can
meaningfully contain the same value more than once. Arrays can be allocated
statically or dynamically.
Static arrays
Static array types are denoted by constructions of the form
array[indexType
1
, ..., indexType
n
] of baseType
where each indexType is an ordinal type whose range does not exceed 2GB. Since the
indexTypes index the array, the number of elements an array can hold is limited by
the product of the sizes of the indexTypes. In practice, indexTypes are usually integer
subranges.
In the simplest case of a one-dimensional array, there is only a single indexType. For
example,
var MyArray: array[1..100] of Char;
declares a variable called MyArray that holds an array of 100 character values. Given
this declaration, MyArray[3] denotes the third character in MyArray. If you create a
static array but don’t assign values to all its elements, the unused elements are still
allocated and contain random data; they are like uninitialized variables.
A multidimensional array is an array of arrays. For example,
type TMatrix = array[1..10] of array[1..50] of Real;
is equivalent to
type TMatrix = array[1..10, 1..50] of Real;
Whichever way TMatrix is declared, it represents an array of 500 real values. A
variable MyMatrix of type TMatrix can be indexed like this: MyMatrix[2,45]; or like
this: MyMatrix[2][45]. Similarly,
packed array[Boolean,1..10,TShoeSize] of Integer;
is equivalent to
packed array[Boolean] of packed array[1..10] of packed array[TShoeSize] of Integer;
The standard functions Low and High operate on array type identifiers and variables.
They return the low and high bounds of the array’s first index type. The standard
function Length returns the number of elements in the array’s first dimension.
A one-dimensional, packed, static array of Char values is called a packed string.
Packed-string types are compatible with string types and with other packed-string
types that have the same number of elements. See “Type compatibility and identity”
on page 5-37.
An array type of the form array[0..x] of Char is called a zero-based character array.
Zero-based character arrays are used to store null-terminated strings and are
compatible with PChar values. See “Working with null-terminated strings” on
page 5-14.