Explain System Boot

Q1. What is System Boot?

Ans. The procedure of starting a computer by loading the kernel is known as booting the system. On most computer systems, a small piece of code known as the bootstrap program or bootstrap loader locates the kernel, loads it into main memory, and starts in execution.


Explain System Calls

Q1. What is meant by System Calls?

Ans. System calls provide an interface to the services made available by an operating system. These calls are generally available as routines written in C and C++, although certain low-level tasks (for example, tasks where hardware must be accessed directly), may need to be written using assembly language instructions.

Operating System as Virtual Machine

Q1. Explain how operating system acts as a Virtual Machine?

Ans. The fundamental idea behind a virtual machine is to abstract the hardware of a single computer (the CPU, memory, disk drives, network interface cards and so forth) into several different execution environments, thereby creating the illusion that each separate execution environment is running its own private computer.

By using CPU scheduling and virtual-memory techniques, an operating system can create the illusion that a process has its own processor with its own (virtual) memory.

There are several reasons for creating a virtual machine, all of which are fundamentally related to being able to share the same hardware yet run several different execution environments (that is, different operating system) concurrently.




Operating System as Virtual Machine

Figure: Virtual Machine

Layered Approach

Q1. What is Layered Approach?

Ans. A system can be made modular in many ways. One method is the layered approach, in which the operating system is broken up into number of layers (levels). The bottom layer (layer 0) is the hardware; the highest (layer N) is the user interface.


Figure: Layered Approach

The main advantage of the layered approach is simplicity of construction and debugging. The layers are selected so that each uses functions (operations) and services of only lower-level layers.

Smart Card Operating System

Q1. Write in short about Smart Card Operating System?

Ans. The smallest operating systems run on smart cards, which are credit card-sized devices containing a CPU chip. They have very severe processing power and memory constraints. Some are powered by contacts in the reader into which greatly limits what they can do. Some of them can handle only a single function, such as electronic payments, but others can handle multiple functions on the same smart card.

Some of these cards can handle multiple Java applets at the same time, leading to multiprogramming and the need to schedule them. Resource management and protection also become an issue when two or more applets are present at the same time. These issues must be handled by the operating system present on the card.


Embedded Operating System

Q1. What is Embedded Operating System?

Ans. Embedded systems run on the computers that control devices that are not generally thought of as computers and which do not accept user-installed software.

Typical examples are microwave ovens, TV sets, cars, DVD recorders, cell phones, MP3 players.

Systems such as QNX and VxWors are popular in this domain.

Hard Real-Time System

Q3. What is Hard Real-Time System?

Ans. If the action absolutely must occur at a certain moment (or within a certain range), we have a hard real-time system. Many of these are found in industrial process control, avionics, military and similar application areas. These systems must provide absolute guarantees that a certain action will occur by a certain time.