View source for Type descriptor

'''Type descriptors''' are used to define [[Data type|data types]] in [[LabVIEW]]. Simplest types consist of only ''TypeDesc ID'', but more advanced ones have additional properties describing them. Compound types also contain references to the sub-types they include.

From the LabVIEW Help:

LabVIEW associates each wire and terminal on the block diagram with a data type. LabVIEW keeps track of this type with a structure in memory called a ''type descriptor''. This type descriptor is a sequence of 32-bit integers that can describe any data type in LabVIEW. Numeric values are written in hexadecimal format, unless otherwise noted.

'''Note:''' The help text above explain how ''Type descriptors'' are stored in memory when a [[VI|VI file]] is loaded. Their [[Flattening|flattened]] form conserves space and mostly uses values smaller than 32-bit.

== List of TD types ==

{| class="wikitable"
! TypeDesc ID
! Description
! Data Type
|-
|0x00
|Void type, stores no data
| [[Void data type]]
|-
|0x01
|Integer with signed 1 byte (8 bit) data
| [[I8 data type]]
|-
|0x02
|Integer with signed 2 byte (16 bit) data
| [[I16 data type]]
|-
|0x03
|Integer with signed 4 byte (32 bit) data
| [[I32 data type]]
|-
|0x04
|Integer with signed 8 byte (64 bit) data
| [[I64 data type]]
|-
|0x05
|Integer with unsigned 1 byte (8 bit) data
| [[U8 data type]]
|-
|0x06
|Integer with unsigned 2 byte (16 bit) data
| [[U16 data type]]
|-
|0x07
|Integer with unsigned 4 byte (32 bit) data
| [[U32 data type]]
|-
|0x08
|Integer with unsigned 8 byte (64 bit) data
| [[U64 data type]]
|-
|0x09
|Floating point with single precision 4 byte data
| [[SGL data type]]
|-
|0x0A
|Floating point with double precision 8 byte data
| [[DBL data type]]
|-
|0x0B
|Floating point with extended (quad precision) data
| [[EXT data type]]
|-
|0x0C
|Complex floating point with 8 byte data
| [[CSG data type]]
|-
|0x0D
|Complex floating point with 16 byte data
| [[CDB data type]]
|-
|0x0E
|Complex floating point with extended (quad precision) data
| [[CXT data type]]
|-
|0x15
|Enumerated UInt8
| [[Enum U8 data type]]
|-
|0x16
|Enumerated UInt16
| [[Enum U16 data type]]
|-
|0x17
|Enumerated UInt32
| [[Enum U32 data type]]
|-
|0x19
|Unit Float32
| 
|-
|0x1A
|Unit Float64
| 
|-
|0x1B
|Unit FloatExt
|
|-
|0x1C
|Unit Complex64
|
|-
|0x1D
|Unit Complex128
|
|-
|0x1E
|Unit ComplexExt
|
|-
|0x20
|Boolean value stored on 2 bytes (16 bit), rarely used
|
|-
|0x21
|Boolean value stored on 1 byte (8 bit)
| [[Boolean data type]]
|-
|0x30
|String value
| [[String data type]]
|-
|0x31
|Variation of String value, probably never used
|
|-
|0x32
|Path value, used for disk paths, sometimes for URLs
| [[Path data type]]
|-
|0x33
|Picture data
| [[Picture data type]]
|-
|0x34
|CString
|
|-
|0x35
|PasString
|
|-
|0x37
|Tag
|
|-
|0x3F
|SubString
|
|-
|0x40
|Array
|
|-
|0x41
|Array Data Ptr
|
|-
|0x4F
|SubArray
|
|-
|0x50
|Cluster, storing several sub-TDs in a sequence
| [[Cluster data type]]
|-
|0x53
|Variant data type
| [[Variant data type]]
|-
|0x54
|Measurement (Waveform) data; has [[Waveform descriptor|multiple sub-types]]
| [[Waveform data type]]
|-
|0x5E
|Complex fixed point number
|
|-
|0x5F
|Fixed point number
| [[Fixed-point data type]]
|-
|0x60
|Block
|
|-
|0x61
|Type block
|
|-
|0x62
|Void block
|
|-
|0x63
|Aligned block
|
|-
|0x64
|Repeated block, stores amount of repeats and one sub-TD to be repeated
|
|-
|0x65
|Alignment marker
|
|-
|0x70
|Refnum; has [[Refnum descriptor|multiple sub-types]], each with different set of properties
| [[Reference data type]]
|-
|0x73
|Set Collection
| [[Set data type]]
|-
|0x74
|Map Collection
| [[Map data type]]
|-
|0x80
|Ptr
|
|-
|0x83
|Ptr to
|
|-
|0x84
|Ext Data
|
|-
|0xA0
|Array interface
|
|-
|0xA1
|Interface to data
|
|-
|0xF0
|Function
|
|-
|0xF1
|TypeDef
|
|-
|0xF2
|PolyVI
|
|}

==External links==

*[http://zone.ni.com/reference/en-XX/help/371361B-01/lvconcepts/type_descriptors/ LabVIEW 8.2 Help>>Type Descriptors]
*[http://zone.ni.com/reference/en-XX/help/371361B-01/lvconcepts/how_labview_stores_data_in_memory/ LabVIEW 8.2 Help>>How LabVIEW Stores Data in Memory]

[[Category:LabVIEW internals]]
[[Category:Data types]]