Character and string types
Free Pascal supports several types of characters and strings.
AnsiChar
A variable of type AnsiChar is exactly 1 byte in size, and contains one ASCII character.
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WideChar
A variable of type WideChar, also referred to as UnicodeChar. is exactly 2 bytes in size, and contains one (part of) Unicode character in UTF-16 encoding. Note: it is impossible to encode all Unicode code points in 2 bytes. Therefore, 2 WideChars may be needed to encode a single code point.
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PChar
A variable of type PChar is basically a pointer to a Char type, but allows additional operations. PChars can be used to access C-style null-terminated strings, e.g. in interaction with certain OS libraries or third-party software.
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PWideChar
A variable of type PWideChar is a pointer to a WideChar variable.
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String
The type string may refer to ShortString or AnsiString, depending from the {$H} switch. If the switch is off ({$H-}) then any string declaration will define a ShortString. It size will be 255 chars, if not otherwise specified. If it is on ({$H+}) string without length specifier will define an AnsiString, otherwise a ShortString with specified length.
ShortString
Short strings have a maximum length of 255 characters. The length is stored in the character at index 0.
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AnsiString
Ansistrings are strings that have no length limit. They are reference counted and are guaranteed to be null terminated. Internally, a variable of type AnsiString is treated as a pointer: the actual content of the string is stored on the heap, as much memory as needed to store the string content is allocated.
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UnicodeString
Like AnsiStrings UniCodeStrings are reference counted, null-terminated arrays, but they are implemented as arrays of WideChars instead of regular Chars.
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