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CHAPTER 3 DECLARATION OF TYPES AND STORAGE CLASSES

User’s Manual U15556EJ1V0UM

3.2.1 Structure specifier and union specifier

Both the structure specifier and union specifier indicate a collection of named members (objects). These member

objects can have different types from one another.

(1) Structure specifier

The structure specifier declares a collection of two or more different types of variables as one object. Each type

of object is called a member and can be given a name. For members, continuous areas are reserved in the

order of their declaration.

Align data is inserted by specifying the -RP option.

A structure is declared as follows. The declaration will not yet allocate memory since it does not have a list of

structure variables.

For the definition of the structure variables, refer to CHAPTER 7 STRUCTURES AND

UNIONS.

struct

identifier {member declaration list};

Example of structure declaration

struct tnode {

int count;

struct tnode *left, *right;

};

(2) Union specifier

The union specifier declares a collection of two or more different types of variables as one object. Each type of

object is called a member and can be given a name. The members of a union overlap each other in area,

namely, they share the same area.

A union is declared as follows. The declaration will not yet allocate memory since it does not have a list of union

variables. For the definition of the union variables, refer to CHAPTER 7 STRUCTURES AND UNIONS.

union

identifier {member declaration list};

Example of union declaration

union

u_tag

{

int var1 ;

long var2 ;

};

Each member object can be any type other than the incomplete types or function types. A member can be

declared with the number of bits specified. A member with the number of bits specified is called a bit field.

In this compiler, extended functions related to bit field declaration have been added. For details, refer to 11.5

(19) Bit field declaration.

78IV Datasheet(PDF) 55 Page - NEC