Skip to main content

fseek( ) method in C language

In order to access the file directly the file handling function fseek( ) is used. Access is nothing but to seek. So, it is easy to remember the function for direct access. The syntax of the function fseek( ) is as follows:

int fseek( FILE *fp, long offset, int whence)

fp is the file pointer
offset is the number of bytes to skip
whence can be replaced with SEEK_SET- from beginning
                                                SEEK_CUR- from current position
                                                SEEK_END - from the end
This position repositions the file or record pointer from the whence position by offset bytes on the file stream fp. The function returns 0 on success or non-zero on unsuccessful.

The following program gives the idea of using the fseek( ) function.

/* Program to display the details of the students using fseek( ) in the binary file "studb.dat" */

main ( )
struct Stud
int rollno, marks[5];
char fname[25];
float avg;
typedef struct Stud STUDENT ; /* renaming the data type struct Stud to Student */
int idx;
FILE *fp;
STUDENT s; /* s is the structure variable to read/write student's data */
fp = fopen("studb.dat","rb"); /* Read mode to scan the records from the binary file "studb.dat" */
if(fp == NULL)
printf("File opening error....");
clrscr( );       /* To clear the screen and to display heading */
fseek(fp,2*sizeof(s),SEEK_CUR);  /* to remove to 3rd record */
fread(&s,sizeof(s),1,fp);  /* to read 3rd record directly */
exit(1);  /* To come out of the loop, at the end of the file */
printf("%4d %26s",s.rollno,s.fname); /* Data is displayed on the screen */
printf("%6d",s.marks[idx]);   /* Next set of Data is displayed */
printf("%8.2f \n",s.avg);  /* Avg is displayed and new line generated for the next record */


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 …