How Can I Develop Own Boot Manager And Convert It Into Iso File Which Is Bootable By Cd Or Usb?

Sir, Can u please tell me how to start the process so that i can continue.

Sir , I have developed the boot manager but it is not working. My code and steps are shown below:

bits 16 ; 16-bit Real Mode
org 0x7c00 ; BIOS boot origin

jmp main ;Jump to start main() entry-point

;;;;;;;;;;;;;;
; Variables
;;;;;;;;;;;;;;

Message db "Hello World, booting from low-level 16-bit...", 0x0
MessageB db "Fisnik's own bootloader program written in x86 assembly language.", 0x0
AnyKey db "Press any key to reboot...", 0x0

;Print characters to the screen
Println:
lodsb ;Load string
or al, al
jz complete
mov ah, 0x0e
int 0x10 ;BIOS Interrupt 0x10 - Used to print characters on the screen via Video Memory
jmp Println ;Loop
complete:
call PrintNwL

;Prints empty new lines like '\n' in C/C++
PrintNwL:
mov al, 0 ; null terminator '\0'
stosb ; Store string

;Adds a newline break '\n'
mov ah, 0x0E
mov al, 0x0D
int 0x10
mov al, 0x0A
int 0x10
ret

;Reboot the Machine
Reboot:
mov si, AnyKey
call Println
call GetPressedKey

;Sends us to the end of the memory
;causing reboot
db 0x0ea
dw 0x0000
dw 0xffff

;Gets the pressed key
GetPressedKey:
mov ah, 0
int 0x16 ;BIOS Keyboard Service
ret

;Bootloader entry-code
main:
cli ;Clear interrupts
;Setup stack segments
mov ax,cs
mov ds,ax
mov es,ax
mov ss,ax
sti ;Enable interrupts

;Print the first characters
mov si, Message
call Println

mov si, MessageB
call Println

call PrintNwL
call PrintNwL

call Reboot

times 510 - ($-$$) db 0 ;Fill the rest of the bootloader with zeros
dw 0xAA55 ;Boot signature