Hi Everyone!
i'm trying to boot a toy os from the usb stick and i'm using dd to copy bootloader to the usb
dd.exe bs=512 count=3 if=bootloader.bin of=//./USBDrive: ------> to copy boot loader to the pendrive and it works
and i've copyied kernel file to the pendrive.
when i boot from the pendrive my boot loader is throwing a read error(it's not finding my kernel...!)

i'm following same procedure to copy bootloader and kernel to floppy disk and it works fine but i've problem with pendrive
please Help........

When you say you have copied the kernel file, did you use dd to place it or the host OS (windows/unix) ? Are you loading the kernel using file system lookup or absolute addressing?

i'm using windows as host os to copy kernel and I'm loading kernel using file system lookup

When you say system lookup, do you mean fat, if so you need different code than floppy, as the usb fob will be formated with fat16 or fat32.
You also have the problem that you are over writing BPB of the fat.
The default BPB that you get with demo boot loaders, is for fat12.

i have tried mike gonta's fat32 usb boot loader still same result..

Dumb question. Does dd make a mbr and does USB use mbr's to boot?

Whether or not you use an MBR is up to you. The BIOS will not enforce any requirement on the boot sector other than the last two byte signature requirement.

My initial search for the standards for bios / usb boot bring up various tools for creating bootable this and that. Any suggestions

This is not 100% true, for example if you boot using USB under floppy emulation and your boot code does not have a BPB, it will not boot.
If it supports usb hdd emulation, it works with or without BPB.

This is from 100's of test on real PC.

Good question. USBDrive: could be placed in partition or in whole disk. In first case the partition could be not marked as active. And I hope that "dd ..." command writes BPB taken from the disk.