Face-off with Size of ()

In C programming, the unary operator sizeof() returns the size of its operand in bytes. The sizeof() operator is discussed in detail in this article, along with illustrative examples of code.

S izeof() is used extensively in the C programming language. It is a compile-time unary operator, which can be used to compute the size (in bytes) of any data type of its operands. The operand may be an actual type-specifier (such as char or ints) or any valid expression. The sizeof() operator returns the total memory allocated for a particular object in terms of bytes. The resultant type of the sizeof() operator is size_t. Sizeof() can be applied both for primitive data types (such as char, ints, floats, etc) including pointers and also for the compound data types (such as structures, unions, etc).

Usage

The sizeof() operator can be used in two different cases depending upon the operand types. Let me elaborate this with syntax, examples and sample codes.

Case 1: When the operand is a type-name

When sizeof() is used with ‘type-name’ as the operand (such as char, int, float, double, etc), it returns the amount of memory that will be used by an object of that type. In this case, the operand should be enclosed within parenthesis. The sizeof operator is used when the operand is a type-name as shown in Table 1.

Illustration: The sample demo code is shown below (Code 1), and the output of the code when I run it in my system is shown in Figure 1.

Code 1

1 #include <stdio.h> 2 #include <stddef.h> 3 4 int main() 5{ 6 printf(“Sizeof(char) : %lu\n”, (long unsigned ) sizeof(char));

7 printf(“Sizeof(int) : %lu\n”, (long unsigned ) sizeof(int));

8 printf(“Sizeof(float) : %lu\n”, (long unsigned ) sizeof(float));

9 printf(“Sizeof(double) : %lu\n”, (long unsigned ) sizeof(double));