Operating System

 What is an operating system ? Where is this used ? Name some operating systems that you have come across? 

An operating system is software that manages the computer hardware . The hardware must provide appropiate mechanisms to ensure the correct operation of the computer system and to prevent user programs from interfering with the proper operation of the system 

The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.

Operating systems

Quick links

Operating System ABCs
Operating System types
Operating System overviews
Troubleshooting
Operating System Q&A
Operating System definitions
Apple news
Linux and Unix news
Microsoft news

Operating system ABCs

An operating system, or OS, is a software program that enables the computer hardware to communicate and operate with the computer software. Without a computer operating system, a computer would be useless.

Operating system types

As computers have progressed and developed so have the operating systems. Below is a basic list of the different operating systems and a few examples of operating systems that fall into each of the categories. Many computer operating systems will fall into more than one of the below categories.

GUI - Short for Graphical User Interface, a GUI Operating System contains graphics and icons and is commonly navigated by using a computer mouse. See the GUI definition for a complete definition. Below are some examples of GUI Operating Systems.

System 7.x
Windows 98
Windows CE

Multi-user - A multi-user operating system allows for multiple users to use the same computer at the same time and different times. See the multi-user definition for a complete definition for a complete definition. Below are some examples of multi-user operating systems.

Linux
Unix
Windows 2000

Multiprocessing - An operating system capable of supporting and utilizing more than one computer processor(e.g intel, AMD). 
Below are some examples of multiprocessing operating systems.

Linux
Unix
Windows 2000

Multitasking - An operating system that is capable of allowing multiple software processes to run at the same time. Below are some examples of multitasking operating systems.

Unix
Windows 2000

Multithreading - Operating systems that allow different parts of a software program to run concurrently. Operating systems that would fall into this category are:

Linux
Unix
Windows 2000

Troubleshooting

Common questions and answers to operating systems in general can be found on the below operating system question and answers. All other questions relating to an operating system in particular can be found through the operating system page.

Linux and Variants
MacOSMS-DOS
IBM OS/2 Warp
Unix and Variants
Windows CE
Windows 3.x
Windows 95
Windows 98
Windows 98 SE
Windows ME
Windows NT
Windows 2000
Windows XP
Windows Vista
Windows 7

Operating system listing

Below is a listing of many of the different operating systems available today, the dates they were released, theplatforms they have been developed for and who developed them.

Operating system	Date first released	Platform	Developer
AIX and AIXL	Unix and Linux history.	Various	IBM
AmigaOS	Currently no AmigaOS history.	Amiga	Commodore
BSD	Unix and Linux history.	Various	BSD
Caldera Linux	Unix and Linux history.	Various	SCO
Corel Linux	Unix and Linux history.	Various	Corel
Debian Linux	Unix and Linux history.	Various	GNU
DUnix	Unix and Linux history.	Various	Digital
DYNIX/ptx	Unix and Linux history.	Various	IBM
HP-UX	Unix and Linux history.	Various	Hewlett Packard
IRIX	Unix and Linux history.	Various	SGI
Kondara Linux	Unix and Linux history.	Various	Kondara
Linux	Unix and Linux history.	Various	Linus Torvalds
MAC OS 8	Apple operating system history.	Apple Macintosh	Apple
MAC OS 9	Apple operating system history.	Apple Macintosh	Apple
MAC OS 10	Apple operating system history.	Apple Macintosh	Apple
MAC OS X	Apple operating system history.	Apple Macintosh	Apple
Mandrake Linux	Unix and Linux history.	Various	Mandrake
MINIX	Unix and Linux history.	Various	MINIX
MS-DOS 1.x	MS-DOS history.	IBM	Microsoft
MS-DOS 2.x	MS-DOS history.	IBM	Microsoft
MS-DOS 3.x	MS-DOS history.	IBM	Microsoft
MS-DOS 4.x	MS-DOS history.	IBM	Microsoft
MS-DOS 5.x	MS-DOS history.	IBM	Microsoft
MS-DOS 6.x	MS-DOS history.	IBM	Microsoft
NEXTSTEP	Apple operating system history.	Various	Apple
OSF/1	Unix and Linux history.	Various	OSF
QNX	Unix and Linux history.	Various	QNX
Red Hat Linux	Unix and Linux history.	Various	Red Hat
SCO	Unix and Linux history.	Various	SCO
Slackware Linux	Unix and Linux history.	Various	Slackware
Sun Solaris	Unix and Linux history.	Various	Sun
SuSE Linux	Unix and Linux history.	Various	SuSE
System 1	Apple operating system history.	Apple Macintosh	Apple
System 2	Apple operating system history.	Apple Macintosh	Apple
System 3	Apple operating system history.	Apple Macintosh	Apple
System 4	Apple operating system history.	Apple Macintosh	Apple
System 6	Apple operating system history.	Apple Macintosh	Apple
System 7	Apple operating system history.	Apple Macintosh	Apple
System V	Unix and Linux history.	Various	System V
Tru64 Unix	Unix and Linux history.	Various	Digital
Turbolinux	Unix and Linux history.	Various	Turbolinux
Ultrix	Unix and Linux history.	Various	Ultrix
Unisys	Unix and Linux history.	Various	Unisys
Unix	Unix and Linux history.	Various	Bell labs
UnixWare	Unix and Linux history.	Various	UnixWare
VectorLinux	Unix and Linux history.	Various	VectorLinux
Windows 2000	Microsoft Windows history.	IBM	Microsoft
Windows 2003	Microsoft Windows history.	IBM	Microsoft
Windows 3.X	Microsoft Windows history.	IBM	Microsoft
Windows 7	Microsoft Windows history.	IBM	Microsoft
Windows 95	Microsoft Windows history.	IBM	Microsoft
Windows 98	Microsoft Windows history.	IBM	Microsoft
Windows CE	Microsoft Windows history.	PDA	Microsoft
Windows ME	Microsoft Windows history.	IBM	Microsoft
Windows NT	Microsoft Windows history.	IBM	Microsoft
Windows Vista	Microsoft Windows history.	IBM	Microsoft
Windows XP	Microsoft Windows history.	IBM	Microsoft
Xenix	Unix and Linux history.	Various	Microsoft

Components of Operating Sytem:

There are three main components:

1.control programs

2.sytem service programs

3.utility programs

CONTROL PROGRAMS

A. Control Programs 
control & maintain the operation of computer 
1. Initial program loader (IPL) 
Program in the form of firmware (software stored in ROM) 
Computer ON, then electronic chip is automatically activated & IPL read the boot sector routine (BSR), reside in the primary memory

B. System Service Program 
Support control programs 
Divided into three portions 
Linkage Editor 
Librarian 
Input/Output control system 
C. Utility Programs 
e.g. 
MS-DOS : Fdisk, FORMAT, ATTRIB, BACKUP, FIND

Process flows from getting a requirement to designing a software package

The international standard for describing the method of selecting, implementing and monitoring the life cycle for software is ISO/IEC 12207.

Planning

An important task in creating a software program is extracting the requirements or requirements analysis ^[1]. Customers typically have an abstract idea of what they want as an end result, but not what software should do. Skilled and experienced software engineers recognize incomplete, ambiguous, or even contradictory requirements at this point. Frequently demonstrating live code may help reduce the risk that the requirements are incorrect.

Once the general requirements are gathered from the client, an analysis of the scope of the development should be determined and clearly stated. This is often called a scope document.

Certain functionality may be out of scope of the project as a function of cost or as a result of unclear requirements at the start of development. If the development is done externally, this document can be considered a legal document so that if there are ever disputes, any ambiguity of what was promised to the client can be clarified.

Implementation, testing and documenting

Implementation is the part of the process where software engineers actually program the code for the project.

Software testing is an integral and important phase of the software development process. This part of the process ensures that defectsare recognized as soon as possible.

Documenting the internal design of software for the purpose of future maintenance and enhancement is done throughout development. This may also include the writing of an API, be it external or internal. The software engineering process chosen by the developing team will determine how much internal documentation (if any) is necessary.Plan-driven models (e.g., Waterfall) generally produce more documentation than Agile models.

[edit]Deployment and maintenance

Deployment starts after the code is appropriately tested, approved for release, and sold or otherwise distributed into a production environment. This may involve installation, customization (e.g. by setting parameters to the customer's values), testing, and possibly an extended period of evaluation.^{[citation needed]}

Software training and support is important, as software is only effective if it is used correctly.^{[citation needed]}

Maintaining and enhancing software to cope with newly discovered faults or requirements can take substantial time and effort, as missed requirements may force redesign of the software.^{[citation needed]}

30 Technical Interview questions for IT Recruiters

General Technical questions
Q1. What is an operating system ? Where is this used ? Name some operating systems that you have come across? 
Q2. What are the components of an OS ? Name at least 3 components
Q3 . What is GUI stands for ?
Q4. Do you understand the difference between Platform and Framework ? Is it different or same ?
Q5. Give me some examples of IT Software Products .
Q6. Do you understand the different between IT services and IT Product based companies ? Name few companies in these categories. 
Q7. Why Customers prefer to develop their applications using Java or Dot net frame work . Give your answers with Business / commercial perspective.
Q8. What do you understand by Embedded systems ? Do you use any of these in your day to day life.
Q9. Have you ever worked on Testing Requirement ? If yes, what are the types of Testing Tools that you know. 
Q10. Your thoughts on Data warehousing - what it is ? Name some tools associated with DW.
Q11. What does ERP stands for and what does it do in an Enterprise. 
Q12. What is Open Source Technology  ? Your understanding about this .
Q13. Do you understand Real Time Operating System ? Give Some examples. Which are all the companies in this domain?
Q14.What is 3 Tier architecture's concept? 
Q15. Your understanding about GSM, CDMA, 3G, 4G, VOIP, in Telecom domain ?
Q16. What is the expansion of SDLC ? 2 lines about SDLC
Q17. Do you understand the role of Business Analyst , Technical Architect, System Architect, Data Architect, Database Administrator, Product Manager, Project Manager, Program Manager in an IT company? 
Q18. If you have ever done SAP hiring, can you name the Modules that you have worked ? 
Q19. What is the expansion of ABAP , Where is this used ? 
Q20.What are the certification courses available in the field of Networking ? 
Q21. Are you aware of PMP ? Who is the certifying authority ? 
Q22. Is there any certifications for Product Managers ? 
Q23. What is the expansion of CRM? Give some examples of CRM Product .
Q24. What is SCM ? Example of SCM software 
Q25. Can you tell me recent Mergers and Acquisition that happened in IT industry ?
Q26. Do you have Linkedin contacts ? With how many are you connected ? 
Q27. Have you heard of the term Web 2.0 ? 
Q28. What is Cloud Computing ? Is it a Product or Service ? Who are all the major players ?
Q29. Have you heard of SOA and SOAP ? 
Q30. Name the Banking product developed by Infosys & I-flex respectively.

Company

A company is a business organization. It is an association or collection of individual real persons and/or other companies, who each provide some form of capital.

There are various types of company that can be formed in different jurisdictions, but the most common forms of company (generally formed by registration under applicable companies legislation) are:

§  A company limited by guarantee. Commonly used where companies are formed for non-commercial purposes, such as clubs or charities. The members guarantee the payment of certain (usually nominal) amounts if the company goes into insolvent liquidation, but otherwise they have no economic rights in relation to the company. This type of company is common in England. A company limited by guarantee may be with or without having share capital.

§  A company limited by shares. The most common form of company used for business ventures. Specifically, a limited company is a "company in which the liability of each shareholder is limited to the amount individually invested" with corporations being "the most common example of a limited company. This can be a public company or private company."^[1] This type of company is common in England.

§  A company limited by guarantee with a share capital. A hybrid entity, usually used where the company is formed for non-commercial purposes, but the activities of the company are partly funded by investors who expect a return. This type of company may no longer be formed in the UK, although provisions still exist in law for them to exist.^[6]

§  A limited-liability company. "A company—statutorily authorized in certain states—that is characterized by limited liability, management by members or managers, and limitations on ownership transfer", i.e., L.L.C.^[1]

§  An unlimited company with or without a share capital. A hybrid entity, a company where the liability of members or shareholders for the debts (if any) of the company are not limited. In this case doctrine of veil of incorporation does not apply.

Less commonly seen types of companies are:

§  Companies formed by letters patent. Most corporations by letters patent are corporations sole and not companies as the term is commonly understood today.

§  charter corporations. Before the passing of modern companies legislation, these were the only types of companies. Now they are relatively rare, except for very old companies that still survive (of which there are still many, particularly many British banks), or modern societies that fulfil a quasi regulatory function (for example, the Bank of England is a corporation formed by a modern charter).

§  Statutory Companies. Relatively rare today, certain companies have been formed by a private statute passed in the relevant jurisdiction.

Private Limited Companies (Ltd)

A private limited company is owned privately by a small group of people such as a family. A private limited company can not trade its shares on the stock market. Private limited companies can operate through just one director but it must have at least 2 shareholders.

The share capital for a private limited company has to be £50 000 or less (there is no minimum). A private limited company has to use the letters Ltd after its name so that people dealing with the company know that they are dealing with a private limited company.

Although private limited companies are usually small in size, they have to produce accounts and send them to registrar of companies annually. Furthermore unlike a sole trader, private limited companies have to pay auditors, hold meetings as stipulated in the Companies Act and share profits between all of the shareholders.

Public Limited companies (PLC)

A public limited company is able to trade on the stock market but in order to gain plc status the company must achieve the following;

Minimum share capital of £50000,
Minimum of two directors,
Its name must contain “plc” or “private limited company”
Secure a trading certificate from the Companies House

The ability to offer shares on the stock market makes it easier to raise capital; however the accounts of the company are in the public domain. All financial records, including the director's reports must be audited and available to the Registrar of Companies at the Companies House and to all who want to scrutinise them. Furthermore the company is vulnerable to take-overs as rivals have the option to purchase shares.

Ltd company is otherwise known as public limited company and pvt ltd company is a private limited company. Under public limited there are private sector company and public sector company.

The Public Sector Public sector’s organizations are budgeted and run by state. They are often called as state organizations. The primary objective of these organizations is to serve the public not to earn profit. Finances are offered freely for the uplift of society. In other words, they involve in social welfare. Organizations of public sector include educational institutes, health services, security providing organizations, national defence, financing etc.

The Private Sector 

Private sector encompasses organizations with primary objective of profit earning and further divided in to two kinds:

Non-Limited CompaniesNon-limited companies do not involve complicated business concepts. There are few formalities found in this type of company, which can be set at the start of business. These formalities are opted by the selection of owner, like, be either a sole trader or start business with partners on partnership basis and the owner  will be personally liable for all of the debts if the business fails. Non-limited companies are free of legal bounding. There is no legal requirement for non-limited companies to make any of their financial information public. Non-limited companies are commonly termed as "businesses".

Limited Companies Limited companies can be either privately owned when they are referred to as Limited (often abbreviated to Ltd) or publicly owned. Some publicly owned can sell shares to members of the public on the stock exchange, unlike Ltd's that cannot do in the same way. The liability for both limited and publicly owned companies is restricted. This means that incase of failure of any company, the liability of the company's shareholders is limited to the value of the shares and not to the personal funds or assets of the business owners. Or, in the case of companies limited by guarantee in which no share capital is involved, the liability of its members is limited up to a specific level that their members wish to contribute to the assets of a company in the event of it being wound up. Please note here that for limited companies, generally used term is “Company” so people automatically understand the nature of company existence. All Limited companies are legally required to submit Company Accounts and Annual Returns every year. These documents are filed at an executive agency of the Department of Trade and Industry (DTI) called Companies House. This information is available to the public. A limited company has similar rights to a person; for example it can buy assets, own property, and it can sue or be sued independently of its directors. It can have detrimental information registered against it too.

The difference between pvt ltd and public ltd company is in the no. of shareholders and transferability of shares. In pvt ltd the minimum no. of shareholders is 2 and maximum is 50 excluding the past and present employees who holds shares . Whereas in public limited the minimum no. of shareholders is 7 and there is no maximum limit.

In the case of public limited co., the shares are freely transferable but it is not so in private limited company.

Some of the strigent requirements which are applicable to public limited companies are not there in the case of private limited companies.

Public sector company is a company where the central govt or state govt or both of them combined together holds the majority of shares. But in Private sector companies the private individuals or business houses holds the majority of shares.

Industry

Industry is often classified into three sectors: primary or extractive, secondary or manufacturing, and tertiary or services

Industries can be classified on the basis of raw materials, size and ownership.

• Raw Materials: Industries may be agriculture based, Marine based, Mineral based, Forest based.
• Size: It refers to the amount of capital invested, number of people employed and the volume of production.
• Ownership: Industries can be classified into private sector, state owned or public sector, joint sector and co-operative sector

Industry is divided into four sectors. They are:

Sector	Definition
Primary	This involves the extraction of resources directly from the Earth, this includes farming, mining and logging. They do not process the products at all. They send it off to factories to make a profit.
Secondary	This group is involved in the processing products from primary industries. This includes all factories—those that refine metals, produce furniture, or pack farm products such as meat.
Tertiary	This group is involved in the provision of services. They include teachers, managers and other service providers.
Quaternary	This group is involved in the research of science and technology. They include scientists.
Quinary Sector	Some consider there to be a branch of the quaternary sector called the quinary sector, which includes the highest levels of decision making in a society or economy. This sector would include the top executives or officials in such fields as government, science, universities, nonprofit, healthcare, culture, and the media.

ISIC (Rev.4) stands for International Standard Industrial Classification of all economic activities, the most complete and systematic industrial classification made by United Nations Statistics Division.

ISO 9000

The ISO 9000 family of standards are related to quality management systems and designed to help organizations ensure that they meet the needs of customers and other stakeholders.^[1] The standards are published by ISO, the International Organization for Standardization, and available through National standards bodies while meeting statutory and regulatory requirements. ISO 9000 deals with the fundamentals of quality management systems,^[2] including the eight management principles^[3][2] on which the family of standards is based. ISO 9001 deals with the requirements that organizations wishing to meet the standard have to fulfill.^[4]

Third party certification bodies provide independent confirmation that organizations meet the requirements of ISO 9001. Over a million organizations worldwide^[5] are independently certified, making ISO 9001 one of the most widely used management tools in the world today. Despite widespread use, however, the ISO certification process has been criticized^[6][7] as being wasteful and not being useful for all organizations

ISO Versions:

ISO 9001:1987 Model for quality assurance in design, development, production, installation, and servicing was for companies and organizations whose activities included the creation of new products.

ISO 9000:1994 emphasized quality assurance via preventive actions, instead of just checking final product, and continued to require evidence of compliance with documented procedures

ISO 9001:2000 combined the three standards—9001, 9002, and 9003—into one, called 9001.  The 2000 version also demanded involvement by upper executives in order to integrate quality into the business system and avoid delegation of quality functions to junior administrators. Another goal was to improve effectiveness via process performance metrics.

ISO 9001:2008 basically renarrates ISO 9001:2000. The 2008 version only introduced clarifications to the existing requirements of ISO 9001:2000 and some changes intended to improve consistency with ISO 14001:2004.

Audit:

Two types of auditing are required to become registered to the standard: auditing by an external certification body (external audit) and audits by internal staff trained for this process (internal audits). The aim is a continual process of review and assessment to verify that the system is working as it is supposed to; to find out where it can improve; and to correct or prevent problems identified. It is considered healthier for internal auditors to audit outside their usual management line, so as to bring a degree of independence to their judgments.

NASSCOM

The National Association of Software and Services Companies (NASSCOM) is a trade association of Indian Information Technology (IT) andBusiness Process Outsourcing (BPO) industry.^[1] Established in 1988, NASSCOM is a non-profit organization focused on promoting sustainable growth for the industry and to harness IT and Communications technologies for inclusive and balanced growth.

• Encourage members to provide world-class quality products, services and solutions in India and overseas and help build brand equity for the Indian IT software and services industry.
• Taking effective steps to campaign against software piracy.
• Provide an ideal forum for overseas and domestic companies to explore the vast potential available for Joint Ventures, Strategic Alliances, Marketing Alliances, Joint Product Development, etc., by organising Business Meets with delegations of various countries.
• Work actively with Overseas Governments, Embassies to make the Visa and Work Permit Rules more "India Industry Friendly".
• Disseminate various policies, market information and other relevant statistics by sending more than 200 circulars (annually) to all members.
• Involve membership participation in various forums of Nasscom on subjects such as HRD, Technology, Exports, Domestic Market, E-Governance, IT Enabled Services, IPR, Finance, Government Policies, Quality, etc.