Data type

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General

This page provides an assortment of data types in Free Pascal.

A data type is a template for a data field.

The data type of a field defines how the compiler and processor interpret it's content.

The visibility of a data field depends on the location of it's declaration.

Integer types

Unsigned types

Data fields of unsigned integral types can only contain positive integral numbers.

• UInt8 - Range: (0 .. 255)
• Byte - Range: (0 .. 255)
• UInt16 - Range: (0 .. 65535)
• Word - Range: (0 .. 65535)
• NativeUInt - Range: depends on the processor type.
• DWord - is equivalent to Longword.
• Cardinal - is equivalent to Longword.
• UInt32 - Range: (0 .. 4294967295)
• Longword - Range: (0 .. 4294967295)
• UInt64 - Range: (0 .. 18446744073709551615)
• QWord - Range: (0 .. 18446744073709551615)

Signed types

Data fields of signed integral types can contain positive and negative integral numbers.

• Int8 - Range: (-128 .. 127)
• ShortInt - Range: (-128 .. 127)
• Int16 - Range: (-32768 .. 32767)
• SmallInt - Range: (-32768 .. 32767)
• Integer - Range: is equivalent either to Smallint or Longint (for 16 respectively 32 bit processors).
• Int32 - Range: (-2147483648 .. 2147483647)
• NativeInt - Range: depends on the processor type.
• Longint - Range: (-2147483648 .. 2147483647)
• Int64 - Range: (-9223372036854775808 .. 9223372036854775807)

Floating-point types

Data fields of a floating-point type can contain:

1. positive and negative integral numbers with possible round-off errors.
2. positive and negative floating-point numbers.

• Single - Range: (1.5E-45 .. 3.4E38)
• Real - Range: depends on the platform.
• Real48 - Range: 2.9E-39 .. 1.7E38
• Double - Range: (5.0E-324 .. 1.7E308)
• Extended - Range: depends on the platform.
• Comp - Range: (-2E64+1 .. 2E63-1)
• Currency - Range: (-922337203685477.5808 .. 922337203685477.5807)

Boolean types

Data fields of boolean type contain truth values.

• Boolean - Range: (True, False), 8 Bit
• ByteBool - Range: (True, False), 8 Bit
• WordBool - Range: (True, False), 16 Bit
• LongBool - Range: (True, False), 32 Bit

Enumeration types

Data fields of an enumeration type are "lists" (enumerations...) of integral unsigned constants.

• Enum Type - Range: (integral data types)

Char types

Char types with single byte encoding

• Char - Constant length: 1 byte, representation: 1 character.
• ShortString - Maxmimum length: 255 characters.
• String - Maxmimum length: Shortstring or Ansistring (depends in the used compiler switch).
• PChar - Pointer to a null-terminated string without length restriction.
• AnsiString - No length restriction.
• PAnsiChar - Pointer to a null-terminated string without length restriction.

See the overview of the different character and string types.

Char types with multi byte encoding

(The encoding with 2 or 4 bytes is system dependent.

• WideChar - Constant length: 2 or 4 bytes, representation: 1 character.
• WideString - No length restriction.
• PWideChar - Pointer to a null-terminated wide string without length restriction.
• UnicodeChar - Constant length: 2 or 4 bytes, representation: 1 character.
• UnicodeString - No length restriction.
• PUnicodeChar - Pointer to a null-terminated Unicode string without length restriction.

See the overview of the different character and string types.

Variant types

• Variant
• Olevariant

Constants

• Untyped constants
  • Const - Only simple data types can be used.
• Typed constants
  • Const - Simple data types as well as records and arrays can be used.
• Resource Strings
  • Resourcestring - Used for localisation (not available in all compiler modes).

Structural types

• Array - The size of the array depends on the type and the number of elements it contains.
• Record - A combination of multiple data types.
• Set - A set of elements of an ordinal type; the size depends on number of elements it contains.

Subrange types

• subrange types are a subset of a base type.

Pointer

• Pointer - The size depends on the processor type.

Classes and objects

• Object - Developed under Turbo Pascal 5.5 for DOS and the precursor of class.
• Class - Developed under Delphi 1.0 for Windows and the successor of object.

See also

• Pascal basics