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CHAPTER 5 OPERATORS AND EXPRESSIONS

User’s Manual U15556EJ1V0UM

(4) sizeof operators

Unary Operators

sizeof Operator

FUNCTION

The sizeof operator returns the size of a specified object in bytes. The return value is governed by the data type

of the object and the value of the object itself is not evaluated.

The value to be returned by an unsigned char or signed char object (including its qualified type) on which a

sizeof operation is performed is 1. With an array type object, the return value will be the total number of bytes in

the array. With a structure or union type object, the result value will be the total number of bytes that the object

would occupy including bytes necessary to pad out to the next appropriate alignment boundary.

The type of the sizeof operation result is an integral type and its name is size_t. This name is defined in the

<stddef.h> header. The sizeof operator is used mainly to allocate memory areas and transfer data to/from the

I/O system.

SYNTAX

sizeof

unary-expression

sizeof

(type-name)

EXAMPLE

The following example finds the number of elements of an array by dividing the total number of bytes in the array

by the size of a single element. Num becomes 5.

int num;

char array[ ]= {0, 1, 2, 3, 4};

void func(void){

num = sizeof array / sizeof array [0] ;

}

NOTE

An expression that has a function type or incomplete type and a left-side value that refers to a bit field object

cannot be used as the operand of this operator.

78IV Datasheet(PDF) 83 Page - NEC