What is the role of sizeof in c language

sizeof is used in C language to get the number of bytes of a data type or variable. Its function is as follows: Get the number of bytes of a basic data type. Get the number of bytes of an array element. Get the number of bytes in a structure or union. Get the number of bytes of the data type pointed to by the pointer variable. Allocate memory.

The role of sizeof in C language

sizeof is an operator in C language, used to obtain The number of bytes occupied by the data type or variable. It is a compile-time operator that calculates and returns the size of a specified data type or variable during the compile phase.

Function:

• Get the number of bytes of the basic data type: For example, sizeof(int) returns bytes of type int number.
• Get the number of bytes of the array element: sizeof(array name) Returns the number of bytes occupied by each element in the array.
• Get the number of bytes of the structure or union: sizeof(structure name) or sizeof(union name) Returns the total number of bytes occupied by all members in the structure or union Section number.
• Get the number of bytes of the data type pointed to by the pointer variable: sizeof(*pointer variable) Returns the number of bytes occupied by the data type pointed to by the pointer variable.
• Allocate memory: sizeof can be used with functions such as malloc() to dynamically allocate memory.

Syntax:

<code class="c">sizeof(数据类型或变量)</code>

Example:

<code class="c">#include <stdio.h>

int main() {
  int i;
  int *p;

  printf("sizeof(int): %ld\n", sizeof(int));
  printf("sizeof(i): %ld\n", sizeof(i));
  printf("sizeof(*p): %ld\n", sizeof(*p));

  return 0;
}</code>

Output:

<code>sizeof(int): 4
sizeof(i): 4
sizeof(*p): 4</code>

In this In the example:

• sizeof(int) returns the number of bytes of type int, which is 4.
• sizeof(i) returns the number of bytes occupied by variable i, which is also 4.
• sizeof(*p) returns the number of bytes occupied by the data type (int) pointed to by pointer variable p, which is 4.

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