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Top 10 List of Week 01

1. Concurrency in operating system
   Concurrency is the execution of the multiple instruction sequences at the same time. It happens in the operating system when there are several process threads running in parallel. The running process threads always communicate with each other through shared memory or message passing. Concurrency results in sharing of resources result in problems like deadlocks and resources starvation. It helps in techniques like coordinating execution of processes, memory allocation and execution scheduling for maximizing throughput.

2. Synchronization in operating system
   Process Synchronization means sharing system resources by processes in a such a way that, Concurrent access to shared data is handled thereby minimizing the chance of inconsistent data. Maintaining data consistency demands mechanisms to ensure synchronized execution of cooperating processes.

3. Mass storage
   Mass storage refers to various techniques and devices for storing large amounts of data. The earliest storage devices were punched paper cards, which were used as early as 1804 to control silk-weaving looms. Modern mass storage devices include all types of disk drives and tape drives. Mass storage is distinct from memory, which refers to temporary storage areas within the computer. Unlike main memory, mass storage devices retain data even when the computer is turned off.

4. Protection and security in operating system
   Protection and security requires that computer resources such as CPU, softwares, memory etc. are protected. This extends to the operating system as well as the data in the system. This can be done by ensuring integrity, confidentiality and availability in the operating system. The system must be protect against unauthorized access, viruses, worms etc.

5. I/O system in operating system
   Management of I/O devices is a very important part of the operating system - so important and so varied that entire I/O subsystems are devoted to its operation. ( Consider the range of devices on a modern computer, from mice, keyboards, disk drives, display adapters, USB devices, network connections, audio I/O, printers, special devices for the handicapped, and many special-purpose peripherals. )

6. Clustered systems in operating system
   Clustered systems are similar to parallel systems as they both have multiple CPUs. However a major difference is that clustered systems are created by two or more individual computer systems merged together. Basically, they have independent computer systems with a common storage and the systems work together.

7. Difference between asymmetric and symmetric multiprocessing
   In asymmetric multiprocessing, the processors are not treated equally. In symmetric multiprocessing, all the processors are treated equally.

8. Multithreading and multicore
   Multithreading and Multicore are different pieces of terminology that apply to different areas of computing. Multicore refers to a computer or processor that has more than one logical CPU core, and that can physically execute multiple instructions at the same time. A computer’s “core count” is the total number of cores the computer has: computers may have multiple processors, each of which might have multiple cores; the core count is the total number of cores on all of the processors. Multithreading refers to a program that can take advantage of a multicore computer by running on more than one core at the same time. In general, twice as many cores equals twice as much computing power (for programs that support multithreading) though some problems are limited by factors other than CPU usage; these problems will not experience gains that are as dramatic from multithreading.

9. Copyleft software
   Copyleft is a general method for making a program (or other work) free (in the sense of freedom, not “zero price”), and requiring all modified and extended versions of the program to be free as well. The simplest way to make a program free software is to put it in the public domain, uncopyrighted. This allows people to share the program and their improvements, if they are so minded

10. System programs in operating system
    The system programs are used to program the operating system software. While application programs provide software that is used directly by the user, system programs provide software that are used by other systems such as SaaS applications, computational science applications etc.