24-12-2012, 05:53 PM
System Software
System Software.ppt (Size: 286.31 KB / Downloads: 38)
SOFTWARE :
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.
Specific kinds of system software include:
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.
Assemblers:
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
Loader
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.
Macros
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
Text Editors
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.
User interface
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
Typical editor structure
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.