Difference between revisions of "Data type"
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− | + | {{Data type}} | |
− | + | =General= | |
− | + | This page provides an assortment of data types in Free Pascal. | |
− | |||
− | |||
− | |||
− | |||
− | |||
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− | + | A '''data type''' is a template for a [[Data field|data field]]. | |
+ | |||
+ | The data type of a field defines how the compiler and processor interpret it's content. | ||
+ | |||
+ | The visibility of a [[Data field|data field]] depends on the location of it's declaration. | ||
+ | |||
+ | =Integer types= | ||
+ | |||
+ | ==Unsigned types== | ||
+ | |||
+ | [[Data field]]s 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 field]]s of signed integral types can contain positive '''and''' negative integral numbers. | ||
+ | |||
+ | * [[Int8]] - Range: (-128 .. 127) | ||
+ | * [[Shortint|ShortInt]] - Range: (-128 .. 127) | ||
+ | * [[Int16]] - Range: (-32768 .. 32767) | ||
+ | * [[Smallint|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|LongInt]] - Range: (-2147483648 .. 2147483647) | ||
+ | * [[Int64]] - Range: (-9223372036854775808 .. 9223372036854775807) | ||
+ | |||
+ | =Floating-point types= | ||
+ | |||
+ | [[Data field]]s of a floating-point type can contain: | ||
+ | |||
+ | # positive '''and''' negative integral numbers with possible round-off errors. | ||
+ | # 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 field]]s of boolean type contain truth values. | ||
+ | |||
+ | * [[Boolean]] - Range: (True, False), 8 Bit | ||
+ | * [[Bytebool|ByteBool]] - Range: (True, False), 8 Bit | ||
+ | * [[Wordbool|WordBool]] - Range: (True, False), 16 Bit | ||
+ | * [[Longbool|LongBool]] - Range: (True, False), 32 Bit | ||
+ | |||
+ | =Enumeration types= | ||
+ | |||
+ | [[Data field]]s 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|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|AnsiString]] - No length restriction. | ||
+ | * [[Pansichar|PAnsiChar]] - Pointer to a null-terminated string without length restriction. | ||
+ | |||
+ | See the overview of the different [[Character and string types|character and string types]]. | ||
+ | |||
+ | == Char types with multi byte encoding== | ||
+ | |||
+ | (The encoding with 2 or 4 bytes is system dependent.<br> | ||
+ | |||
+ | * [[WideChar]] - Constant length: 2 or 4 bytes, representation: 1 character. | ||
+ | * [[Widestring|WideString]] - No length restriction. | ||
+ | * [[Pwidechar|PWideChar]] - Pointer to a null-terminated wide string without length restriction. | ||
+ | * [[Unicodechar|UnicodeChar]] - Constant length: 2 or 4 bytes, representation: 1 character. | ||
+ | * [[Unicodestring|UnicodeString]] - No length restriction. | ||
+ | * [[Punicodechar|PUnicodeChar]] - Pointer to a null-terminated Unicode string without length restriction. | ||
+ | |||
+ | See the overview of the different [[Character and string types|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|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]] |
Latest revision as of 17:06, 29 August 2021
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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:
- positive and negative integral numbers with possible round-off errors.
- 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
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.