From OSDev Wiki
Padding for a Floppy is even easier than for a HardDisk - all we need to know is the desired final size.
; ; Pad/Floppy.inc ; ; This file performs the necessary padding to generate a .flp or .img file. ; All of the hard work has been done: all we need to do is generate ; sufficient extra bytes to make the resultant output file large enough to ; satisfy programs like earlier versions VMware. ; These programs use the file size to determine the size of the simulated floppy, ; and from there the geometry to use (number of sectors per track, number of ; tracks per side, etc.) SEGMENT Floppy ;Floppy.Format EQU 720 ;Floppy.Format EQU 1200 Floppy.Format EQU 1440 ;Floppy.Format EQU 2880 Floppy.Padding EQU Floppy.Format*1024 - Demo.Size ; From kiB to bytes TIMES Floppy.Padding DB 00h Floppy.Size EQU $ - $$ %assign Demo.Size Demo.Size + Floppy.Size