Step by step process to create a program that boots at start-up in assembly language and making bootable pendrive or floppy drive

1. Step 1
as test.S -o test.o
ld –Ttext 0x7c00 --oformat=binary test.o –o test.bin
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as test.S –o test.o: Converts the given assembly code into
respective object code which is an intermediate code generated
by the assembler before converting into machine code.
The --oformat=binary switch tells the linker you want your output
file to be a plain binary image
The -Ttext 0x7c00 tells the linker you want your "text" (code
segment) address to be loaded to 0x7c00 and thus it calculates
the correct address for absolute addressing.

3. Step 2
//Writing to USB
dd if=test.bin of=/dev/sdb1
//For booting from virtual disk in vmware
dd if=/dev/zero of=floppy.img bs=512 count=2880
dd if=test.bin of=floppy.img
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Utility dd : Converts and copies the file

5. Step 3
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Enter BIOS
Modify the boot order to bring your usb device
to the top.
BOOT !

6. Step 3
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Enter BIOS
Modify the boot order to bring your usb device
to the top.
BOOT !