mikroC

mikroC - C Compiler for Microchip PIC microcontrollers

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Sizeof Operator

Prefix unary operator sizeof returns an integer constant that gives the size in bytes of how much memory space is used by its operand (determined by its type, with some exceptions).

Operator sizeof can take either a type identifier or an unary expression as an operand. You cannot use sizeof with expressions of function type, incomplete types, parenthesized names of such types, or with an lvalue that designates a bit field object.

Sizeof Applied to Expression

If applied to expression, size of the operand is determined without evaluating the expression (and therefore without side effects). Result of the operation will be the size of the type of the expression’s result.

Sizeof Applied to Type

If applied to a type identifier, sizeof returns the size of the specified type. Unit for type size is the sizeof(char) which is equivalent to one byte. Operation sizeof(char) gives the result 1, whether the char is signed or unsigned.

sizeof(char)

/*

returns

1

*/

sizeof(int)

/*

returns

2

*/

sizeof(unsigned long)

/*

returns

4

*/

page

112

When the operand is a non-parameter of array type, the result is the total number of bytes in the array (in other words, an array name is not converted to a pointer type):

int i, j, a[10];

 

 

 

 

//...

 

 

 

 

j

= sizeof(a[1]);

/*

j

=

sizeof(int) = 2 */

i

= sizeof(a);

/*

i

=

10*sizeof(int) = 20 */

If the operand is a parameter declared as array type or function type, sizeof gives the size of the pointer. When applied to structures and unions, sizeof gives the total number of bytes, including any padding. Operator sizeof cannot be applied to a function.

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