Skip to main content

Structure in C language

Introduction to structures


We know that an array is a collection of similar data items such as int, float, char etc. If more number of Data items of same data type are grouped, we normally use arrays. For example, the marks of 6 students can be stored using array as shown below:

Int marks[6]={86,99,95,93,87,91};

The ordinary variables and arrays can handle variety of situations. But, in real world, we often deal with entities that are collection of dissimilar data types. For example, suppose we want to have the data related to a student. We may be interested in:
  • Name of the student            (char array, string type)
  • Roll number                        (int type)
  • Average marks                    (float type)
Note that the above data is a collection of various items of dissimilar data types(heterogeneous). So, arrays cannot be used (because, array is a collection of similar data types, homogeneous in nature). This is where, the structure are used.

Structure and its definition


Now, we shall see “ what is a structure? What is the syntax of a structure?”
Definition : A structure is defined as a collection of logically related (generally heterogenous) Variables under a single name. All these variables may contain data items of similar or dissimilar
Data types. Using these variables each item of a structure can be selected. Each variable in the
Structure represents an item and is called member or field or element of the structure. Each field
Has a type.


The general format or syntax of a structure is shown below:

Structure in C Programming


Where
  • Struct is keyword which tells the compiler that a structure is being defined.
  • Member1, member2,… are called members of the structure. They are also called fields or Elements of the structure.
  • The members are declared within curly braces. It is called body of the structure. The Members can be any of data types such as int, char, float etc.
  • There should be semicolon at the end of closing brace.
Example: Structure definition for storing student data.
Assume the student data consists of the following:
  •    Name of the student: Name is made up of sequence of characters. Ex: “Jecob Lefore”
  •    Roll number: It is of type integer Ex:1101
  •    Average marks: It is of type float Ex: 93.45
Since the above information is related to student and all the above information is logically related to
A student, we can use the structure. The structure definition to hold the information of student is
Shown below:
                               Struct student
                               {
                                          Char name [10];
                                          Int    rollno;
                                          Float   avg;
                             };
In the above example, observe the following points:

  • Struct is the keyword.
  • Student is called the name of the structure. The name of the structure is also called structure tag.
  • Name, rollno and avg are called fields of the structure. They are also called members of Structure and are associated with data types char, int and float.

The structure definition does not reserve any space  in memory for the members. So, it is called a  structure template and memory will  not be allocated for the template. This is pictorially represented as shown below:

structure template and memory will  not be allocated for the template

                                                          
Note : the various items in a structure can be same or different data types. But, all the items should be logically related. Do not combine un-related data.

For example, for the above structure definition, let us have filed number_of_wheels. The field number_of_wheels is in no way related to student data and hence has to  be avoided.

Comments

Popular posts from this blog

difference between structure and union in C Language

In c language article we will see the difference between union and structure. Both are the user define datatype in c language. See the table which is mentioned below: ASP.NET Video Tutorial Series Structure Union1.The keywordstruct is used to define a structure 1. The keyword union is used to define a union. 2. When a variable is associated with a structure, the compiler allocates the memory for each member. The size of structure is greater than or equal to the sum ofsizes of its members. The smaller members may end with unused slack bytes. 2. When a variable is associated with a union, thecompiler allocates thememory by considering the size of the largest memory. So, size of union is equal to the size of largest member. 3. Each member within a structure is assigned unique storage area of location. 3. Memory allocated is shared by individual members of union. 4. The address of each member will be in ascending order This indicates that memory for each member will start at different offset v…

Difference between Linear search and Binary Search in c language

SQL Video Channel : Download all SQL Video



Binary Search Linear Search Works only on sorted items. such as  1,2,3,4,5,6  etc
Works on sorted as well as unsorted items. 12,4,5,3,2,1 etc Very efficient if the items are sorted Very efficient if the items are less and present in the beginning of the list. such as Suppose your list items are : 12,3,4,5,1 and you want to search 12 number then you get beginning in the list. Works well with arrays and not on linked lists. Works with arrays and linked lists.
Number of comparisons are less More number of comparisons are required if the items are present in the later part of the array or its elements are more.

Memory representation of Linked List Data Structures in C Language

Memory representation of Linked List

             In memory the linked list is stored in scattered cells (locations).The memory for each node is allocated dynamically means as and when required. So the Linked List can increase as per the user wish and the size is not fixed, it can vary.

               Suppose first node of linked list is allocated with an address 1008. Its graphical representation looks like the figure shown below:


      Suppose next node is allocated at an address 506, so the list becomes,



  Suppose next node is allocated with an address with an address 10,s the list become,


The other way to represent the linked list is as shown below:




 In the above representation the data stored in the linked list is “INDIA”, the information part of each node contains one character. The external pointer root points to first node’s address 1005. The link part of the node containing information I contains 1007, the address of next node. The last node …