Introduction To Software

Computer needs both hardware and software for its proper functioning. By software we mean computer instructions or data. Software often divided into two categories.

SYSTEM SOFTWARE: includes the operating system and all the utilities that enable the computer to function.

APPLICATION SOFTWARE: includes program that do real work for users. For example, word processing, spread sheet, and database management software.

OPERATING SYSTEM: An operating system manages and coordinates the functions performed by the computer hardware, including CPU, input/output devices, secondary storage devices. Operating systems are most important program that runs on a computer. Every general purpose computer must have an operating system to run other program. In other words operating system is a interface in between user and hardware.

The operating system software must keep track of each hardware resource, determine who gets what, determine when the user will have access to the resources, allocate how much of the resources the is will be given. A single stand alone microcomputer will have a relatively simple operating system, where as a mainframe have one that is far more complex

Types of operating systems

CUI: CHARACTER USER INTERFACE

A character user interface(CUI) or command-line interface (CLI) is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks. This text-only interface contrasts with the use of a mouse pointer with a graphical user interface (GUI) to click on options, or menus on a text user interface (TUI) to select options. This method of instructing a computer to perform a given task is referred to as "entering" a command: the system waits for the user to conclude the submitting of the text command by pressing the "Enter" key. A command-line interpreter then receives, analyses, and executes the requested command.

GUI: GRAPHICAL USER INTERFACE

A graphical user interface (GUI) is a type of user interface item that allows people to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 players, portable media players or gaming devices; household appliances and office equipment with images rather than text commands. A GUI offers graphical icons, and visual indicators, as opposed to text-based interfaces, typed command labels or text navigation to fully represent the information and actions available to a user. The actions are usually performed through direct manipulation of the graphical elements.

Graphical User Interface or the GUI was first developed at Xerox PARC by Alan Kay, Douglas Engelbart, and a group of other researchers. A GUI uses windows, icons, and menus to carry out commands such as opening files, deleting files, moving files, etc. and although many GUI Operating Systems are operated by using a mouse, the keyboard can also be used by using keyboard shortcuts or arrow keys. Unlike a command line operating system like UNIX or MS-DOS, GUI Operating Systems are much easier for end-users to learn and use because commands do not need to be known or memorized. Because of their ease of use, GUI Operating Systems have become the dominant operating system used by end-users today.

A few examples of a GUI Operating Systems:

Microsoft Windows 95,98, XP, Vista, 7
Apple System 7
Apple Mac OS.

Operating systems can be classified as follows:

Batch Processing: in a batch processing system the program of one user is run at a time. The program of another can be taken up only when program of one user is completed. The user can not interact with the computer.

Multi Programming: a large computer may be designed to process a set of independent program concurrently. This technique is called as multiprogramming. In this type of system the operating system transfers a few programs from the disk memory into the main memory. The computer begins the execution of one program, suppose this program requires any peripheral device or some data that is not present in the main memory. Then the computer suspends the first program and takes up another program. When the required data for the first program are available in the main memory, the computer interrupted, now the computer resume the first program after suspending the second program.

Timeshare System: in timeshare system several user work concurrently on the computer. Several terminals are connected to the computer. The computer gives a small slice of time usually 20 milliseconds to each user and attends them in turn. The user does not feel this as the computer works as very high speed. In this system user can interact with the computer.

Multitasking: For real time applications the time share approach of multi-user is not suitable. In multi-user system all user are attended at equal time interval where as for real time applications priority based job scheduling is employed. A high priority task can interrupt a low priority task. In an industry several machines or several processes can be controlled by a computer simultaneously. This is known as multitasking.

Multi Processing System: a computer system having two or more CPU’s is called a multiprocessor system. Such systems are very powerful, fast, and reliable. There are two main types of multiprocessor system, shared memory machine and distributed memory system. In a shared memory machine there is a large memory. In a distributed memory system each processor has a local memory.

Distributed Processing: In a distributed processing system there is a powerful central computer with large memory and high speed printer. In this system however each user has a microcomputer or minicomputer instead of terminals. User performs many tasks locally at the workstation using microcomputer or minicomputer. As the microcomputer and minicomputer are connected to a large computer, the user can use the large computer, its memory or other resources for complex computation which cannot performed by local micro or minicomputers.