Write a program to compute the following equation for values of time.  
 
      y = 2x+3
 
The values of time are stored in the file program.dat and the solution should be displayed on the screen and stored in a file called program.out.
 
Answer
 
  #include stdio.h
  #include stdlib.h
  void main()
    {
    char prompt;
    
     Date: 26th August 2012 
    Version 1.0 
    Function : ASCII file handling       
     Modifications:   none*/
 
  /* Define I/O streams */
  FILE *fptr,*fptw;
  float x,y;
  fptr = fopen("program.dat","r");

  if (fptr == NULL)  
  {
  /* Check for error */
  printf("Cannot find the file program.dat\n\r");
  exit(1);
  }
  fptw = fopen("program.out","w");
  if (fptw == NULL)
  {
    /* Check for error */
 
  printf("Cannot create a new file called program.out");
  fclose(fptr);
  exit(1);
  } 
  while (fscanf(fptr,"%f",&x) != EOF)
  {
  /* This repeats the read till fscanf returns back an End of file marker i.e No 
data left */
   y = 2*x+3;
  printf("X = %f Y=%f\n\r",x,y);
  fprintf(fptw,"X = %f Y=%f\n\r",x,y);
  }
  printf("I have finished the computation\n\r");
  fclose(fptr);
  fclose(fptw); 
  printf("Press and key to exit \n\r");
  scanf("\n%c",&prompt);
  }
 
Original data can be entered using the application 'NOTEPAD', or 'Edit' likewise the output can be read by Notepad or any word processor set to text mode.