Quick start manual

Data types, variables, and constants

5-15

String types

points P to an area of memory that contains a null-terminated copy of “Hello world!”

This is equivalent to

const TempString: array[0..12] of Char = 'Hello world!'#0;

var P: PChar;

P := @TempString[0];

You can also pass string constants to any function that takes value or const

parameters of type PChar or PWideChar—for example StrUpper('Hello world!'). As

with assignments to a PChar, the compiler generates a null-terminated copy of the

string and gives the function a pointer to that copy. Finally, you can initialize PChar

or PWideChar constants with string literals, alone or in a structured type. Examples:

const

Message: PChar = 'Program terminated';

Prompt: PChar = 'Enter values: ';

Digits: array[0..9] of PChar = (

'Zero', 'One', 'Two', 'Three', 'Four',

'Five', 'Six', 'Seven', 'Eight', 'Nine');

Zero-based character arrays are compatible with PChar and PWideChar. When you

use a character array in place of a pointer value, the compiler converts the array to a

pointer constant whose value corresponds to the address of the first element of the

array. For example,

var

MyArray: array[0..32] of Char;

MyPointer: PChar;

begin

MyArray := 'Hello';

MyPointer := MyArray;

SomeProcedure(MyArray);

SomeProcedure(MyPointer);

end;

This code calls SomeProcedure twice with the same value.

A character pointer can be indexed as if it were an array. In the previous example,

MyPointer[0] returns H. The index specifies an offset added to the pointer before it is

dereferenced. (For PWideChar variables, the index is automatically multiplied by

two.) Thus, if P is a character pointer, P[0] is equivalent to P^ and specifies the first

character in the array, P[1] specifies the second character in the array, and so forth;

P[-1] specifies the “character” immediately to the left of P[0]. The compiler performs no

range checking on these indexes.