ADVANCED DATA STRUCTURES PROGRAM • LEVEL 19 — FILES AND FILE ORGANIZATION

Update a Record In Place with fseek

Learn how to update a record in place with fseek using a clear C program.

AdvancedRecord organizationSecondary storage

PROBLEM UNDERSTANDING

Input and expected output

Sample input

No input required

Sample output

10 20 99 40

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int values[]={10,20,30,40};FILE*file=fopen("values.bin","wb+");if(!file)return 1;fwrite(values,sizeof values[0],4,file);int replacement=99;fseek(file,2L*(long)sizeof replacement,SEEK_SET);fwrite(&replacement,sizeof replacement,1,file);rewind(file);fread(values,sizeof values[0],4,file);fclose(file);for(int i=0;i<4;i++)printf("%d%c",values[i],i==3?'\n':' ');return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

10 20 99 40

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Seek directly to the fixed record offset and overwrite only that record.
Display the computed result.

Seek directly to the fixed record offset and overwrite only that record.

EFFICIENCY

Time and space complexity

Time complexity

O(1) update

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.