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MDSplus Data Types

MDSplus supports numerous data types, from simple numeric or text types to complex entities which combine related information in a structure. Some of the data types are used internally for representing things such as data acquisition devices, compiled representations of expressions and data acquisition actions and you may likely never have to interact with these items. Most users will normally be accessing the primitive data types including all integer, floating point or text data types as well as several of the more complicated MDSplus data types such as signals, dimensions, with units, with errors and ranges.

Many of the MDSplus data types consist of structures or records containing two or more fields. There are built in functions in the TDI expression evaluation language for extracting these fields from the structure.

One of the more important data types provided by MDSplus is the signal, DTYPE_SIGNAL. A signal is a structure which combines a value part, optionally a raw data part, and one or more dimension descriptions. Data from measurement devices as well as analysis results are often stored as signals. Many visualization applications will generate plots of signals by plotting the value portion versus the dimensions. The value part of a signal can be an expression which references the raw data part of the signal. Support for transient recorders often use this feature by storing the raw counts values in the raw data part and then put an expression to convert this raw data to engineering units (such as voltage) in the value part of the signal. In the case of the support for a transient record, a representation of the time base would normally be stored in the first dimension part of the signal.

The following table list all the supported types. Click on the data type for more information on each type.

Name Description
Integer Data Types

DTYPE_BU

Unsigned Byte (8-bit)

DTYPE_WU

Unsigned Word (16-bit)

DTYPE_LU

Unsigned Long (32-bit)

DTYPE_QU

Unsigned Quadword (64-bit)

DTYPE_OU

Unsigned Octaword (128-bit)

DTYPE_B

Byte (8-bit)

DTYPE_W

Word (16-bit)

DTYPE_L

Long (32-bit)

DTYPE_Q

Quadword (64-bit)

DTYPE_O

Octaword (128-bit)

Floating Point / Real Data Types

DTYPE_F

32-bit Vax F_FLOAT

DTYPE_D

64-bit Vax D_FLOAT

DTYPE_G

64-bit Vax G_FLOAT

DTYPE_FC

32-bit Vax F_FLOAT complex

DTYPE_DC

64-bit Vax D_FLOAT complex

DTYPE_GC

64-bit Vax G_FLOAT complex

DTYPE_FS

32-bit IEEE Float

DTYPE_FT

64-bit IEEE Float

DTYPE_FSC

32-bit IEEE Float complex

DTYPE_FTC

64-bit IEEE Float complex

Text / String Data Type

DTYPE_T

Text

MDSplus Data Types

DTYPE_ACTION

Action definition

DTYPE_CALL

Call function

DTYPE_CONGLOM

Conglomerate / Device

DTYPE_DIMENSION

Dimension definition

DTYPE_DISPATCH

Dispatch information

DTYPE_FUNCTION

Function reference

DTYPE_IDENT

MDSplus identifier "Ken variable"

DTYPE_METHOD

Invoke device method

DTYPE_NID

32-bit Node Identifier

DTYPE_PARAM

Parameter

DTYPE_PATH

Node specifier (Path)

DTYPE_RANGE

Range

DTYPE_ROUTINE

Routine

DTYPE_SIGNAL

Signal

DTYPE_WINDOW

Window

DTYPE_WITH_ERROR

Attach error to value

DTYPE_WITH_UNITS

Attach units to value