Use Built-In and Predefined Storage Classes to Represent Data in Generated Code

Use built-in storage classes or predefined storage classes in the Embedded Coder^® Dictionary to control the appearance and placement of data elements in your generated code. When choosing a storage class to meet your requirements, consider both the predefined and customizable properties of that storage class. For an overview of each built-in or predefined storage class and its properties, see Choose Storage Class for Controlling Data Representation in Generated Code.

If you have special requirements not met by the listed storage classes and you are generating code for an ERT-based target, you can define and use a new storage class. See Define Service Interfaces, Storage Classes, Memory Sections, and Function Templates for Software Architecture, and Create Storage Classes by Using the Custom Storage Class Designer.

Choose Built-In or Predefined Storage Class Based on Properties

The following table lists key properties to consider when you choose a built-in or predefined storage class to represent your data. While some properties of a particular storage class are customizable, others are predefined and shown explicitly in the table. Here, model refers to the current model containing the data element that the storage class is applied to.

For information about each storage class and its configurable properties (including Owner), see Choose Storage Class for Controlling Data Representation in Generated Code or click the name of the storage class in the table. For information about all storage class properties (except Owner) and their configuration settings, see Embedded Coder Dictionary or click the name of the property in the table.

For storage classes with a customizable HeaderFile property:

• If the storage class has an exported DataScope setting, see Exported Scope Data Declaration File Packaging for more details.

• If the storage class has an imported DataScope setting, see Imported Scope Data Declaration File Packaging for more details.

For storage classes with a customizable DefinitionFile property, see Data Definition File Packaging for more details.

Storage Class	Storage Type	Data Scope	Data Initialization	Header File	Definition File	Owner	Preserve array dimensions
ExportedGlobal	Unstructured	Exported	Auto	model.h	model.c	model	off
ImportedExtern, ImportedExternPointer	Unstructured	Imported	Some signals and states: Dynamic Other data: In external code	Customizable	In external code	model	off
Const, Volatile, and ConstVolatile	Unstructured	Exported	Auto	Customizable	Customizable	Customizable	Customizable
Define, ImportedDefine	Unstructured	Exported	Macro	Customizable	None	model	off
ExportToFile	Unstructured	Exported	Auto	Customizable	Customizable	Customizable	Customizable
ImportFromFile	Unstructured	Imported	In external code	Customizable	In external code	model	Customizable
FileScope	Unstructured	File	Auto	None	model.c	model	Customizable
Localizable	Unstructured	Function or File scope: File Global scope: Exported	Function scope: Static inside function File or global scope: Static outside function	Function or File scope: None Global scope: Customizable	Function scope: Function source file File scope: model.c Global scope: Customizable	model	Customizable
Struct	Structured	Exported	Auto	model.h	model.c	model	off
Bitfield	Structured	Exported	Auto	model.h	model.c	model	off
GetSet	Unstructured	Imported	In external code	In external code	In external code	model	Customizable
CompilerFlag	Unstructured	Imported	Macro	None	None	model	off
Reusable	Unstructured	Customizable	Dynamic	File scope: None Exported or Imported scope: Customizable	File scope: model.c Exported or Imported scope: Customizable	Customizable	off
MultiInstance	Single-instance: Unstructured Multi-instance: Structured	Exported	Single-instance: Auto Multi-instance: None	model.h	Single-instance: model.c Multi-instance: None	model	off

Note

The code generator does not initialize data mapped to the Localizable storage class if both of the following are true:

• The data is represented by a variable of function scope with zero initial value.

• The model configuration parameter Remove local variable initialization to zero value is enabled.

The code generator does not define or initialize data mapped to a storage class whose Owner property is set to a different model name than that of the current model. See Data Definition File Packaging.

Storage Classes and Data Declarations and Definitions

Declarations and definitions of data elements in the generated code depend on properties of the storage class assigned to that data element. The following tables summarize how built-in or predefined storage classes control declaration and definition statements in the code.

Data Declarations and Definitions for Parameters

Storage Class	Declaration	Definition
ExportedGlobal	extern datatype identifier;	datatype identifier = value;
ImportedExtern	extern datatype identifier;	External code
ImportedExternPointer	extern datatype *identifier;	External code
Const	extern const datatype identifier;	const datatype identifier = value;
Volatile	extern volatile datatype identifier;	volatile datatype identifier = value;
ConstVolatile	extern const volatile datatype identifier;	const volatile datatype identifier = value;
Define	#define identifier value	None
ImportedDefine	#define identifier value	None
ExportToFile	extern datatype identifier;	datatype identifier = value;
ImportFromFile	extern datatype identifier;	External code
FileScope	static datatype identifier = value;	static datatype identifier = value;
Struct	Type definition: typedef struct struct_name_tag { datatype identifier; } struct_name_type; Declaration: extern struct_name_type struct_name;	struct_name_type struct_name = {value;}
Bitfield	Type definition: typedef struct struct_name_tag { datatype identifier : nbits; } struct_name_type; Declaration: extern struct_name_type struct_name;	struct_name_type struct_name = {value;}
GetSet	External code	External code
CompilerFlag	None	None
MultiInstance	Single-instance: extern datatype identifier; Multi-instance: typedef struct {datatype identifier;} model_T;	Single-instance: datatype identifier = value; Multi-instance: None

Data Declarations and Definitions for Root-Level I/O Data, Signals, States, and Datastores

Storage Class	Declaration	Definition
ExportedGlobal	extern datatype identifier;	datatype identifier;
ImportedExtern	extern datatype identifier;	External code
ImportedExternPointer	extern datatype *identifier;	External code
Volatile	extern volatile datatype identifier;	volatile datatype identifier;
ExportToFile	extern datatype identifier;	datatype identifier;
ImportFromFile	extern datatype identifier;	External code
FileScope	static datatype identifier;	static datatype identifier;
Localizable	Function scope: datatype identifier; File scope: static datatype identifier; Global scope: datatype identifier;	Function scope: datatype identifier; File scope: static datatype identifier; Global scope: datatype identifier;
Struct	Type definition: typedef struct struct_name_tag { datatype identifier; } struct_name_type; Declaration: extern struct_name_type struct_name;	struct_name_type struct_name;
Bitfield	Type definition: typedef struct struct_name_tag { datatype identifier : nbits; } struct_name_type; Declaration: extern struct_name_type struct_name;	bitfield_name_type bitfield_name;
GetSet	External code	External code
Reusable	File scope: static datatype identifier; Exported or Imported scope: extern datatype identifier;	File scope: static datatype identifier; Exported scope: datatype identifier; Imported scope: External code
MultiInstance	Single-instance: extern datatype identifier; Multi-instance: typedef struct {datatype identifier;} model_T;	Single-instance: datatype identifier; Multi-instance: None

Storage Classes and Data Declaration and Definition File Packaging

Exported Scope Data Declaration File Packaging

The following table summarizes how file placement of data declarations depends on the Data declaration model configuration parameter and the HeaderFile property, if available, for the following storage classes:

• ExportToFile

• Const

• Volatile

• ConstVolatile

• Define

• Localizable (global scope)

• Reusable (exported scope)

Data declaration	HeaderFile	Location
Auto	None	model.h
InSourceFile	None	Define: model.h Other storage class: No declaration generated
InSeparateHeaderFile	None	Header file specified by Data declaration filename, such as global.h
Any setting	my_header.h	my_header.h

Imported Scope Data Declaration File Packaging

The following table summarizes how placement of data declarations depends on the File packaging format model configuration parameter and the HeaderFile property, if available, for the following storage classes:

• ImportedExtern

• ImportedExternPointer

• ImportedFromFile

• Reusable (imported scope)

File packaging format	HeaderFile	Location
Modular	None	model_private.h
Compact	None	model.h
CompactWithDataFile	None	model.h
Any setting	my_header.h	my_header.h

Data Definition File Packaging

The following table summarizes how file placement of data definitions depends on the Data definition model configuration parameter, and the DefinitionFile and Owner properties, if available, for the following storage classes:

• ExportToFile

• Const

• Volatile

• ConstVolatile

• Localizable (global scope)

• Reusable (exported scope)

Data definition	DefinitionFile	Owner	Location
Auto	None	None or current model name	model.c
InSourceFile	None	None or current model name	model.c
InSeparateSourceFile	None	None or current model name	Header file specified by Data definition filename, such as global.c
Any setting	my_source.c	None or current model name	my_source.c
	Any setting	Other model name	No definition generated when Use owner from data object for data definition placement is enabled