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i compile with these instructions in cygwin ..
gcc -c -m32 -B /home/vivek/os/kernel -Wall -nostdlib -nostartfiles -nostdinc -std=gnu99 *.c
as --32 startk.s -o startk.so
ld -m i386pe -T linker.ld startk.so *.o -o kernel


when i boot with bochs it shows unrecognized executable format

Try linking with 'ld -m elf_i386 -T linker.ld startk.so *.o -o kernel'

-JL

it shows
ld : unrecognized emulation mode elf_i386
try i386pe

Do you have included the AOUT kludge in the multiboot header?

.global _loader # making entry point visible to linker

# setting up the Multiboot header - see GRUB docs for details
.set ALIGN, 1<<0 # align loaded modules on page boundaries
.set MEMINFO, 1<<1 # provide memory map
.set FLAGS, ALIGN | MEMINFO # this is the Multiboot 'flag' field
.set MAGIC, 0x1BADB002 # 'magic number' lets bootloader find the header
.set CHECKSUM, -(MAGIC + FLAGS) # checksum required

.align 4
.long MAGIC
.long FLAGS
.long CHECKSUM

# reserve initial kernel stack space
.set STACKSIZE, 0x4000 # that is, 16k.
.comm stack, STACKSIZE, 32 # reserve 16k stack on a quadword boundary

_loader:
mov $(stack + STACKSIZE), %esp # set up the stack
push %eax # Multiboot magic number
push %ebx # Multiboot data structure

call kmain # call kernel proper
hlt # halt machine should kernel retur

it still gives unrecogoised format

for starters, build a GCC Cross-Compiler instead of using that ugly cygwin thing.

Do you understand the meaning of the errors? If you don't understand the basics behind the error messages you are getting, you need to learn a lot more before you set off on your journey. Perhaps you should start with freestanding the parameters you are passing to your tools and the code itself.

It's possible to make a pe kernel.

It's possible to make a pe kernel.

But difficult.

Maybe you are compile your kernel on a x86_64 OS?

That's just my situation.

I sovled this problem by downloading a i386 ld and using it instead of the x64 one.

I renamed the i386 ld into 386-ld, so I use this to link my kernel:

386-ld -Tlink.ld -o kernel.img x.o .xx.o xxx.o

That works perfectly.