Skip to main content

Addition and Subtraction operation in Data Structures through C Language

Addition and Subtraction operation:

After assigning some value (address) to the pointer, such pointer can be used in arithmetic operation only involving addition and subtraction. Be cautious, the addition and subtraction. After assignment whenever a number is added to pointer then a normal addition. The concept will be clear when you see an example.
Consider the following declaration: int A[10], *p: ‘A’ is an array of size 10 of the type integer. ‘p’ is a pointer variable also of the type integer. Name of the array ‘A’ give the base address of array. Now, p=A;    pointer variable p is assigned with base address of array
A[0]    first element of the array
P[0]    also gives first element of array
A[3]    fourth element of the array
P[3]     also gives fourth element of the array

Suppose that base address allocated to array is 3200. Then the value of pointer ‘p’ is 3200. As the array is of the type integer, each element of array consumes 2 bytes of memory and the computer memory is allocated to the array statically (at the time of compilation) and the memory is ‘contiguous’ i.e. continuous. So, the first element address is 3202. Similarly each element of the array differs by size of the data type i.e. 2. Now let us see the concept of pointer addition. Pointer ‘p’ contains address of first element i.e. 3200. If 1 is added to ‘p’ then the resulting value will be 3202 not 3201. It means the address is updated by the size of the element rather then the just 1 .Similarly whenever a number ‘n’ is added to the pointer the result will be the concept. When 0 is added to pointer then it gives the address of ‘0’ number element i.e. first element of the array. When 2 is added to pointer then it gives the address of ‘2’ number element i.e. third element of the array.

 The following looping statement will print the array elements through pointer variable:
The above loop is similar to the following normal looping statements to print the array:

The subtraction operation is similar to the addition operation. If a number is subtracted from the pointer, then the result obtained gives the address of the previous element. Again the result depends on the size of the element. The following loop prints the array in reverse order with the help of pointer subtraction;
      p=&A[9];   /*last element’s address is stored in ‘p’*/

The array can be printed in reverse order using the following normal looping statements:
  For(I=9;I>=0;I--)                              OR                  for(I=9;I>0;I--)
   Printf(“%p”,A[I]);                                                       printf(“%d”,p[I]);

In the similar way the value stored in a pointer changes by:
          1 if the element is of the type ‘char’
          4 if the element is of the type of ‘float’ or ‘long integer’
          8 if the element is of the type ‘double’
During pointer arithmetic involving ‘addition’ and ‘subtraction’. In addition operation the pointer points to the next element’s address where as in subtraction the pointer points to the previous element’s address.  


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 …