(i) Kernel of an Operating system and Non-resident portion of Operating system

An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer – from cellular phones and video game consoles to web server sand supercomputers.

(ii) Command line interface and Graphical user interface of Operating system

User Interface is the term used for specifying how a user interacts with an electronic device, particularly computer. CLI and GUI are the different kinds of user interfaces. Mainly they differ in the graphics employed in the operating system. To perform an operation on the CLI system one has to write a command. On the other hand, in GUI users provided the visual aids (graphics) that include images and icons, which facilitates users to perform a task directly.

User Interface is the term used for specifying how a user interacts with an electronic device, particularly computer. CLI and GUI are the different kinds of user interfaces. Mainly they differ in the graphics employed in the operating system. To perform an operation on the CLI system one has to write a command.

Multiprocessing and Multitasking

• Multiprocessing

Multiprocessing sometimes refers to executing multiple processes (programs) at the same time. This might be misleading because we have already introduced the term “multi programming” to describe that before.

If the underlying hardware provides more than one processor then that is multiprocessing. Several variations on the basic scheme exist, e.g., multiple cores on one die or multiple dies in one package or multiple packages in one system.

• Multitasking

Multitasking has the same meaning of multi programming but in a more general sense, as it refers to having multiple (programs, processes, tasks, threads) running at the same time. This term is used in modern operating systems when multiple tasks share a common processing resource (e.g., CPU and Memory). At any time the CPU is executing one task only while other tasks waiting their turn. The illusion of parallelism is achieved when the CPU is reassigned to another task

Just to make it easy to remember, both multi programming and multitasking operating systems are (CPU) time sharing systems. However, while in multi programming (older OSs) one program as a whole keeps running until it blocks, in multitasking (modern OSs) time sharing is best manifested because each running process takes only a fair quantum of the CPU time.

(iv) Computer Virus and Computer Worms

What is a Computer Virus?

Computer viruses are named after human viruses that spread from person to person. A computer virus is a program made of malicious code that can propagate itself from device to device. Like a cold that alters your well-being, when your computer is infected, it alters the way your computer operates, can destroy your files, or prevent it from working altogether.

When the infected application or file runs in the computer, the virus activates and executes in the system. It continues to replicate and spread by attaching replicas of itself to other files and applications in the system.

What’s a Computer Worm?

Worms are a self-replicating type of malware (and a type of virus) that enter networks by exploiting vulnerabilities, moving quickly from one computer to another. Because of this, worms can propagate themselves and spread very quickly – not only locally, but have the potential to disrupt systems worldwide.

Unlike a typical virus, worms don’t attach to a file or program. Instead, they slither and enter computers through a vulnerability in the network, self-replicating and spreading before you’re able to remove the worm. But by then, they’ll already have consumed all the bandwidth of the network, interrupting and arresting large network and web servers.

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