A digital computer cannot start or boot properly if it does not have which essential system component installed?

Introduction / Context:
This question belongs to computer fundamentals and focuses on the booting process. When a computer is powered on, it runs through a series of steps that end with loading the main software environment where users can work. This process is known as booting. The question checks whether you know which essential component must be available for the boot process to complete successfully and for the computer to be usable by the user.

Given Data / Assumptions:

• The subject is a general purpose digital computer such as a desktop or laptop.
• The question states that the computer cannot boot if a certain component is missing.
• Options include compiler, loader, operating system, assembler and driver package.
• We assume ordinary user level booting where a graphical or command based environment appears for work.

Concept / Approach:
Booting is the process of starting the computer and loading the operating system into main memory. At the lowest level, firmware in the BIOS or UEFI runs first, performs hardware checks and locates bootable media. It then loads the core files of the operating system, such as Windows, Linux or macOS. Without an installed and accessible operating system, the processor has nothing to load that can manage hardware, run applications and provide a user interface. Although compilers, assemblers and loaders are important software tools, they are not required for the basic boot sequence that brings up the main environment for users. Therefore, the key component required for booting is the operating system.

Step-by-Step Solution:

Verification / Alternative check:
If you try to start a new or blank hard disk with no operating system installed, the computer will show error messages and will not reach a usable desktop or command shell. Installation guides for Windows or Linux always make it clear that the first step is to install an operating system; once installed, the computer can boot normally. System diagrams usually show hardware at the bottom, then firmware, then the operating system and finally applications. This layered view confirms that without the operating system layer, user programs cannot run and the standard boot process fails.

Why Other Options Are Wrong:

• Compiler program: A compiler translates high level language code into machine language. It is not required to boot the system.
• Loader program: There is a low level concept of loading programs, but end user machines have the loader implemented as part of the operating system and firmware, not as a separate program the user must install.
• Assembler program: An assembler converts assembly language into machine code. This tool is used by programmers and is not essential for normal booting.
• Device driver package: Drivers are needed for full hardware support but the system can still partially boot without some drivers. The key requirement is the main operating system itself.

Common Pitfalls:
Some learners become confused because in operating system theory, terms like loader and bootstrap loader appear. They may think the loader option refers to the same concept as booting. In exam questions focused on everyday computer use, the intended answer is the operating system that users install, such as Windows or Linux. Another mistake is to assume any important development tool must be present for booting, but tools like compilers are only needed for programming, not for starting the computer. Keeping the boot sequence order in mind helps avoid these errors.

Final Answer:
A computer cannot boot into a usable state if it does not have an Operating system installed and accessible.