A common and must known solution in such conditions is to decorate a bootloader that acts as a program which is a part of the standard OS that hacks the system and stores the substitute OS. Apple took the initiative to use this technique for it’s a/UX Unix implementation and this was copied by different freeware OS and BeOS personal Edition 5.
 
At the second stage boot loader, the tiny and small program is not often called operating system but it is just a second stage boot loader such as NTLDR, LILO or GRUB. It will then be capable of storing the OS in perfect way and at long last shift the execution to it. Then the system will proceed for the initialization and may store device drivers and other programs that are required for the normal operation of the OS. The boot process is complete itself at the time the computer is in good condition to make interaction with the user or the OS is able to run the general applications. The typical modem PCs about in about a minute of which approximately  15 seconds are spent by a power on self test and the primary boot loaders. It is also seen that  the big servers may take couples of minutes to start booting and starting all services.

All the embedded systems especially in the case of automotive applications depend on Flash Boot loaders to make it sure that electronic control unit can be programmed either in production or in service. It is also seen that a Flash Bootloader lives in Flash memory and is the first application to start running after the necessary resetting. It is the fact that the function of the flash boot loaders is to hint whether  an application is ready.  The advantage of the availability of the Flash Bootloader on an ECU is mainly to permit deleting and making new programs for new applications on a single ECU at the time of the up gradation of the application.