5 January 2017

History of OS (Operating System)


The earliest of computers didn't have an operating system.  By the early 1960's, commercial computer vendors were supplying quite extensive tools for streamlining the development, scheduling and execution of jobs on batch processing systems.

Through the 1960's, several concepts were developed which drove the development of operating systems.  The IBM System 360 produced a family of mainframe computer that served consumers with differing capacities and prices.  A single operating system was planned for these computers rather than developing generic programs for every individual model.

This concept of a single OS that will fit an entire product line was crucial for the success of System 360.  In fact, IBM's current mainframe operating systems are distant relatives of this original system.  The advantage to this is that applications written for the OS 360 can still be run on modern machines.

The OS 360 system also contained another important advance affecting today's computers:  the development of a hard disk permanent storage device which IBM called DASD. 

A second key development was the concept of time sharing.  Time sharing involves sharing the resources of expensive computers among multiple computer users interacting in real time with the system.  What that essentially means is that all of the users have the illusion of exclusive access to the machine.  The most famous of time sharing system was called Multics.

Multics served as an inspiration to a number of operating systems developed in the 1970's.  Most notably was the Unix system.  Another commercially popular mini-computer operating system was VMS.

The first microcomputers did not have the capacity or need for the elaborate operating systems that had originally been developed for mainframes and minis.  Smaller operating systems were developed and often loaded from ROM and known as Monitors.

One notable early disk-based OS was CP/M which was supported on many early micro-computers and was largely cloned when MS-DOS was created.  MS-DOS became wildly popular as the operating system chosen for the IBM PC. 

The successive operating systems that came from MS-DOS made Microsoft one of the most profitable companies in the world with the development of Windows.  The only other alternative throughout the 1980's was Mac OS which was tied intimately to the Apple McIntosh computer.

By the 1990s, the microcomputer had evolved to the point where it became increasingly desirable.  Everyone wanted a home computer.  Microsoft had already come out with Windows 95 and 98, but people longed for more power and more options.  Microsoft's response to this change was the development of Windows NT which served as the basis for Microsoft's desktop operating system line that launched in 2001.

Apple was also rebuilding their own operating system on top of Unix core as Mac OS X also released in 2001 developing one of the business world's greatest rivalries. 

Today, our operating systems usually have a graphical user interface (GUI) which uses a pointing device such as a mouse of stylus for input in addition to the keyboard.  Older systems and we mean REALLY OLD use a command line interface asking for commands to be entered via the keyboard.

Both models are centered on a shell which accepts and processes commands from the user.  The user may be asked to click on a button or type in a command upon an on-screen prompt.

By far, the most common operating system in use today is Windows XP, but Microsoft has just released their newest Windows project Windows Vista. Linux is also another popular OS as is Unix.  We'll explore them later on in the book, but each offers its own particular advantages and disadvantages.

Considering the boom of the technology market, it's really a surprise that there are so few operating systems in existence.  There really isn't an easy explanation for this, but it is a reality.  It would only seem logical that with all of the different computer manufacturers out there, there would be more of a choice for an OS than what there is.  It is certainly another anomaly in the world of computer technology.

So what exactly do operating systems do?  Since they really are the brain of the computer, they do quite a bit!

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