Quick start manual

5-14

Delphi Language Guide

String types

system supports Unicode (UCS-2). The Linux operating system supports UCS-4, a

superset of UCS-2. Borland’s RAD products support UCS-2 on both platforms.

The Delphi language supports single-byte and multibyte characters and strings

through the Char, PChar, AnsiChar, PAnsiChar, and AnsiString types. Indexing of

multibyte strings is not reliable, since S[i] represents the ith byte (not necessarily the

ith character) in S. However, the standard string-handling functions have multibyte-

enabled counterparts that also implement locale-specific ordering for characters.

(Names of multibyte functions usually start with Ansi-. For example, the multibyte

version of StrPos is AnsiStrPos.) Multibyte character support is operating-system

dependent and based on the current locale.

Delphi supports Unicode characters and strings through the WideChar, PWideChar,

and WideString types.

Working with null-terminated strings

Many programming languages, including C and C++, lack a dedicated string data

type. These languages, and environments that are built with them, rely on null-

terminated strings. A nul-terminated string is a zero-based array of characters that

ends with NUL (#0); since the array has no length indicator, the first NUL character

marks the end of the string. You can use Delphi constructions and special routines in

the SysUtils unit (see Chapter 8, “Standard routines and I/O”) to handle nul-

terminated strings when you need to share data with systems that use them.

For example, the following type declarations could be used to store null-terminated

strings.

type

TIdentifier = array[0..15] of Char;

TFileName = array[0..259] of Char;

TMemoText = array[0..1023] of WideChar;

With extended syntax enabled ({$X+}), you can assign a string constant to a statically

allocated zero-based character array. (Dynamic arrays won’t work for this purpose.)

If you initialize an array constant with a string that is shorter than the declared length

of the array, the remaining characters are set to #0. For more information about

arrays, see “Arrays” on page 5-19.

Using pointers, arrays, and string constants

To manipulate null-terminated strings, it is often necessary to use pointers. (See

“Pointers and pointer types” on page 5-27.) String constants are assignment-

compatible with the PChar and PWideChar types, which represent pointers to null-

terminated arrays of Char and WideChar values. For example,

var P: PChar;

P := 'Hello world!';