Booting and Dual Booting of Operating System

When a computer or any other computing device is in the powerless state, its operating system remains stored in the secondary storage like Hard Disk or SSD. But, when the computer is started, the operating system must be present in the main memory or RAM of the system.

When a computer system is started, there is a mechanism in the system which loads the operating system from the secondary storage into the main memory or RAM of the system. This is called Booting process of the system.

There are two types of booting depending on the number of operating systems installed on the machine/computer, i.e.

  • Booting

  • Dual Booting

Let us understand, these two concepts in the context of computer booting.

What is Booting of Operating System?

The process of starting a computer or a computing device is called booting. Technically, Booting is a procedure of starting a computer or computer embedded device by loading its operating system from disk into RAM. In other words, Booting is a process of starting a computer system by loading the kernel.

As we mentioned earlier, when computer is switched its operating system is stored in the disc. Therefore, on the starting of the computer system, the operating system has to be loaded into the main memory. For this a special computer program is required which locates and loads the operating system into RAM. This special program is called Bootstrap Loader. It is stored in the ROM (Read Only Memory) of the system.

In modern computer systems, booting can be executed from various devices. The BIOS (Basic Input Output System) of the computer allows users to configure a specific boot order. For example, if there are three disks in the system namely, HDD, CD Drive, and Pen Drive, and the boot order set to these disks in the following order,

  • HDD (Hard Disk Drive)

  • CD Drive

  • Pen Drive

Then the system BIOS will try to boot from HDD first, and if the booting from HDD is failed, then it will try to boot from the CD drive, and if it fails to boot, then finally it will try to boot from the Pen Drive, and in this case also the system fails to boot, then it would not boot at all.

Hence, booting is a startup sequence that starts the computer by loading operating system into RAM when it is turned ON. In booting process, the important operations that the bootstrap loader executes are locating the operating system, loading of OS into main memory, and start its execution.

Now, let us discuss the dual booting process of operating system.

What is Dual Booting in Operating System?

When a single computer system has two operating systems installed on it, then its booting is called dual booting. Actually, such computer systems can have multiple operating systems installed on them. But in such cases, a question arises that how system determines which operating system is to boot?

Such systems have a bootstrap loader that can understand multiple file systems, and can have multiple operating systems in the boot space. It can boot any one operating system present on the disc. Also, the disc have multiple partitions, thus different operating systems can be stored in different partitions. When the computer system is started, a menu list is displayed on the screen by a boot manager program that allows the user to select one operating system to run.


In conclusion, booting is defined as the process of loading the operating system of the computer from disc into the main memory when the computer is started. Whereas, dual booting is advanced version of booting in which two operating systems are installed on a single computer system. The user then select an operating system to run from the boot manager menu.