Array of Structures vs Array within a Structure in C

Last Updated : 15 Jul, 2025

Both Array of Structures and Array within a Structure in C programming is a combination of arrays and structures but both are used to serve different purposes.

Array within a Structure

A structure is a data type in C that allows a group of related variables to be treated as a single unit instead of separate entities. A structure may contain elements of different data types - int, char, float, double, etc. It may also contain an array as its member. Such an array is called an array within a structure. An array within a structure is a member of the structure and can be accessed just as we access other elements of the structure.

Below is a demonstration of a program that uses the concept of the array within a structure. The program displays the record of a student comprising the roll number, grade, and marks secured in various subjects. The marks in various subjects have been stored under an array called marks. The whole record is stored under a structure called a candidate.

Example

The below program demonstrates the use of an array within a structure.

Output

Roll number : 1
Grade : A
Marks secured:
Subject 1 : 98.50
Subject 2 : 77.00
Subject 3 : 89.00
Subject 4 : 78.50

Array of Structures

An array is a collection of data items of the same type. Each element of the array can be int, char, float, double, or even a structure. We have seen that a structure allows elements of different data types to be grouped together under a single name. This structure can then be thought of as a new data type in itself. So, an array can comprise elements of this new data type. An array of structures finds its applications in grouping the records together and provides for fast access.

Below is a demonstration of an array of structures. The array holds the details of the students in a class. The details include the roll number, grade, and marks, which have been grouped under a structure (record). There exists one record for each student. This is how a collection of related variables can be assembled under a single entity to enhance the clarity of code and increase its efficiency.

Example

The below program demonstrates the usage of an array of structures.

Output

Roll number : 1
Grade : A
Average marks : 89.50

Roll number : 2
Grade : C
Average marks : 67.50

Roll number : 3
Grade : B
Average marks : 70.50

Difference between Array of Structures and Array within Structures

Below is the tabular difference between the Array within a Structure and Array of Structures:

Parameter	Array within a Structure	Array of Structures
Basic idea	A structure contains an array as its member variable.	An array in which each element is of type structure.
Syntax	struct class { int ar[10]; } a1, a2, a3;	struct class { int a, b, c; } students[10];
Access	Can be accessed using the dot operator just as we access other elements of the structure.	Can be accessed by indexing just as we access an array.
Access elements syntax	structure.array[index]	array[index].member
Memory Structure	Array within the structure will be stored in sequential memory and structure padding is not dependent on the size of the array.	There will be some empty space between structure elements due to structure padding.