How to use C _ Candle + basic sizeof

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Sizeof () is an operator that determines the type of data or the length of an expression in C _ blank +.

1. Sizeof defines sizeof as an operator (operator) in Cplink +, which returns the number of bytes of memory occupied by an object or type.

The sizeof keyword gives the amount of storage, in bytes, associated with a variable ora type (including aggregate types). This keyword returns a value of type size_t.

-- from MSDN

The return value type is size_t and is defined as: typedef unsigned int size_t in the header file stddef.h

From the definition of sizeof, you can see that sizeof is not a function, because a function call must have a pair of parentheses.

# include int main (void) {int num = 97; printf ("value of sizeof (num = 0):% d\ n", sizeof (num = 0)); printf ("value of num:% d\ n", num); return 0;}

The running result is 4pjm 97; it is not 4pas 0

Note: sizeof is not a unary operator in the standard sense, chain expressions are not supported, and statements within the scope of sizeof will not be compiled into machine code, such as + + in sizeof (num++). Sizeof is not a function either. Sizeof is more like a special macro that is evaluated at compile time.

2. Sizeof usage sizeof has two grammatical forms, as follows:

Sizeof (type_name); / / sizeof (type); sizeof (object); / / or sizeof object all belong to sizeof objects

So:

Int i; sizeof (I); / / reasonable sizeof I; / / reasonable sizeof (int); / / reasonable sizeof int; / / unreasonable

When using sizeof on a type, sizeof type_name is illegal and must be written as sizeof (type_name)

Whether it is a value for an object or a type, the form sizeof () is correct

1) sizeof of basic data types

The basic data types here refer to simple built-in data types such as short, int, long, float, and double.

Because their memory size is related to the system, the values may be different in different systems.

# include using namespace std; int main () {cout