System is a set of interacting or interdependent components forming an integrated whole.

 Computer software, or just software, is a collection of computer programs and related data that provide the instructions to a computer.  Or.. software is a set of programs, procedures, algorithms and its documentation  CLASSIFICATION OF S/W:  Application s/w  Firmware  Middleware  Testware  Device drivers  System software.

 Application software, also known as an application is a software designed to help the user to perform singular or multiple related specific tasks. Ex: word processors, video games.  Middleware: controls and co-ordinates distributed systems.  Firmware: firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices. Typical examples of devices containing firmware range from end-user products such as remote controls or calculators.  Test ware: is software for testing hardware or a software package.

 Device Drivers: device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device.  System software refers to the files and programs that make up your computer's operating system  It consists of variety of programs that support the operation of a computer.  This s/w makes it possible for the user to focus on an application or any other problem to be solved without needing to know the details how the machine works internally.  It is any computer software that provides the infrastructure over which programs can operate. i.e. it manages and controls computer hardware so that application software can perform.

1.Write program in high level language using text editor 2.Translate into machine language using compiler 3.Loader, linker Debugger to correct errors. Macro processors, assembler In networking, send and receive data w/o going into the details how data is transferred “behind the scenes.”

 The system software is installed on your computer when you install your operating system. You can update the software by running programs such as "Windows Update" for Windows or "Software Update" for Mac OS X.  Unlike application programs, however, system software is not meant to be run by the end user.  For example, while you might use your Web browser every day, you probably don't have much use for an assembler program (unless, of course, you are a computer programmer).

 Since system software runs at the most basic level of your computer, it is called "low-level" software.  It generates the user interface and allows the operating system to interact with the hardware. System software is software that basically allows the parts of a computer to work together. Without the system software the computer cannot operate as a single unit.

 Assemblers  Loaders and Linker  Compiler  Macros  Shell  BIOS  Hypervisors: a hypervisor, also called virtual machine monitor (VMM), allows multiple operating systems to run concurrently on a host computer, a feature called hardware virtualization.

 It was difficult to write programs in machine language. So programmers began to use mnemonics(assembly language) for each machine instruction.  Assemblers r used to translate assembly language to machine language.  Source prog.  assembler  Object program

 Is a program that places object programs into the memory and prepares them for execution.  Assembler could place object program, in memory and transfer control to it. But it would waste memory while program is being executed.

 Relieve the programmer of the need to repeat the identical parts of their program.  Permits the programmer to define an abbreviation for the part of his program. And to use the abbreviation(Macro definition) in the program. Compiler: is a program that accepts the program written in high level language(Fortran, Cobol, Algol etc)and produces an object program

 An interactive text editor has become an important part of any computing environment.  It is now increasingly recognized that a text editor should be considered the primary interface to the computer for all types of “knowledge workers” as they compose, organize, study and manipulate computer based information.  Any INTERACTIVE EDITOR is a computer program that allows a user to create and revise a target document.  The term “document” includes computer programs, Text equations, tables, diagrams and photographs– anything that u might find on a printed page.

 But we restrict our attention to “text editors”, in which primary elements being edited are character strings of target text.  Editing process is designed to accomplish four tasks:  Select the part of target document to be viewed and manipulated.  Determine how to format this view and how to display it.  Specify and execute operations that modify the target document.  Update the view appropriately.

 Selection of the part of document to be viewed and edited involves first travelling through the document to locate the area of interest. This task is accomplished by next screen, bottom and find pattern.  Filtering extracts the relevant subset of target doc at the point of interest.  Formatting then determines how result will be seen on the computer.  Actual editing phase.  Save and update.

 User is provided with the conceptual model of editing system.  It provides the abstraction of target documents and its elements, with a set of guidelines describing the effects of operations on these elements..  Line editors  Screen editors(Multiline)  Besides this model, user is concerned with Input devices, Output devices, Interaction Language

 Input devices  Text devices Button devices Locator devices Voice input devices Interaction language Typing oriented or Text command oriented Menu oriented.

 Command language processor: accepts input from user’s i/p devices and analyzes the tokens and syntactic structure of commands.  In editing a document, start of area to be edited is determined by current editing pointer maintained by editing component., which is the collection of modules dealing with the editing tasks.  CEP can be set or reset explicitly by users with travelling commands such as next screen, next para, or implicitly by the system as an side effect of deleting a para.  Travelling component actually performs the setting of current editing and viewing pointers. Thus it determines the point where the viewing and editing filtering begins.

 When a user issues edit command, editing component invokes editing filter  This component filters the doc to generate a new editing buffer based on current editing pointer and editing filter parameters.  Editing parameters (user and system) provide information such as range of text that can be affected.  Similarly, in viewing a document start of the area to be viewed is determined by current viewing pointer maintained by viewing component of editor, which is the collection of modules responsible for determining the next view.  When the display needs to be updated, the viewing component invokes viewing filter. This component generates a new viewing buffer(based on viewing filter parameters)

 Assembly language: Machine dependent Low level language Specific to certain computer system.  Three basic features:  Mnemonic operation codes: eliminates the need to memorize the numeric operation codes.. enables assembler to provide helpful diagnostics. Indication of misspell operation codes.  Symbolic Operands: symbolic names can be associated with the data or instructions. These can be used as operands in assembly statements.  Data declaration: can be declared in variety of notations including Decimal notation.