Size of a structure

The size of a structure in C is the sum of the sizes of its members. The size of a structure type can be determined using the sizeof operator in C.

For example, the following code declares a structure called person with three members: a name, an age, and an address:

struct person {
  char *name;
  int age;
  char *address;
};

The size of the person structure can be determined using the sizeof operator:

sizeof(struct person);

This will return the size of the person structure in bytes, which is the sum of the sizes of the name, age, and address members.

The size of a structure can be affected by padding. Padding is added to a structure to ensure that all of its members are aligned on a word boundary. The size of the padding depends on the size of the members of the structure and the alignment requirements of the compiler.

For example, the following code declares a structure called point with two members: an x-coordinate and a y-coordinate:

struct point {
  int x;
  int y;
};

The size of the point structure is 8 bytes, even though the x and y members are only 4 bytes each. This is because the x and y members are not aligned on a word boundary, so the compiler adds 4 bytes of padding to the structure.

The size of a structure can be calculated by adding the sizes of its members and the padding. However, it is usually easier to use the sizeof operator to determine the size of a structure.

Here are some things to keep in mind when calculating the size of a structure:

• The size of a structure is not always equal to the sum of the sizes of its members. This is because of padding.
• The size of a structure can vary depending on the compiler and the target platform.
• The size of a structure can be affected by the alignment requirements of the compiler.