programming-for-dummies

586
Data Structures
Creating an array
To create an array in Pascal, you must create a variable that represents an
array under the Var section of a program like this:
Var
Arrayname : ARRAY [LOWER..UPPER] OF datatype;
If you wanted to create an array to hold five strings, you could do this:
Var
HitList : ARRAY [1..5] OF string;
If you don’t want your array elements to be numbered from 1 to 5, you could
pick any range of numbers, such as
Var
HitList : ARRAY [25..29] OF string;
Defining different lower and upper ranges for the size of your array gives you
the flexibility of using meaningful array index numbers (such as employee
IDs), but at the risk of making the actual size of the array harder to understand.
An array bounded by 1..5 easily identifies five elements in the array,
but an identical array bounded by 25..29 also identifies five elements in an
array but it’s not as obvious.
You can also create a dynamic array that can change in size while your program
runs. To create a dynamic array, define the array without specifying its
size, such as
Var
Arrayname : ARRAY OF datatype;
Before you can store data in a dynamic array, define its size with the
SetLength command, such as
SetLength (Arrayname, Size);
So if you created a HitList dynamic array, you could define its size to hold
ten items by using the following:
SetLength (HitList, 10);
When you define the size of a dynamic array, you define only the size of the
array because the first element of the array is always 0. When you want to