- 1. SOFTWARE
Computer consists of four basic element hardware, software, firmware and human ware. The hardware of computer system alone is little different to any other complex piece of electronic machinery. The hardware would not work without programs (set of instruction). The software directs and guides the operation of each device including CPU. The set of programs which control the activities of computer system or which may be processed on computer to do some useful work, are called software. As car needs fuel to run. Similarly computer hardware needs software to do anything. Software may be put on disk, cassette, and magnetic tape of Semi-Conductor memory.
So we can say that software is a set of programs documents procedure and routines associated with the operation of computer system. In other words, software means a collection of programs whose objective is to enhance the capabilities of the hardware.
- 2. Classification of software
Software cab be classified into two broad categories: System software and application software. System software performs computer- related tasks such as managing input and output devices; application software performs people- related tasks, such as human resources and marketing.
(I) System software
(II) Application software
SOFTWARE
SYSTEM SOFTWARE APPLICATION SOFTWARE
SYSTEM CONTROL S/W
SYSTEM SUPPORT S/W
SYSTEM DEVELOPMENT S/W
GENERAL PURPOSE S/W SPECIAL APPLICATION BASED S/W
System Software
System software performs the basic functions necessary to start and operate a computer. It controls and monitors the various activates and resources of a computer and makes it easier and more efficient to use the computer. System software is classified into three categories.
- System control software (Programs that manage system resources and functions)
- System support software (Programs that support the execution of various application)
- System development software (programs those system developers in designing and developing information systems).
(I) System Control Software: System control includes programs that monitor, control, coordinate and manage the resources and functions of a computer system. The most important system software is the operating system and DBMS.
(II) System Support Software: System support software is software that support or facilitates the smooth and efficient operation of a computer. There are four major categories of systems support software: Utility programs, language translators, database management systems and performance statistics software.
(III) System Development Software: System development Software helps system developers design and build better system. An example is computer-aided software engineering or CASE a collection of programs that assist developers in developing information system.
Application Software
Application software cab be divided into two categories: general purpose software and application dedicated software. Application software is designed to perform people-related tasks such as payroll, inventory and sales analysis. There are two type of application software: general-purpose (designed for general application, such as payroll and so on) and special Application Based Software.
- 1. General Purpose Software: General purpose software is used to perform common business applications such as word-processing graphics, payroll [and accounting].
- 2. Special Application Based Software: The second type of applications software is special application –Based software which includes specialized, application designed for every specific purpose. Such a program cannot easily be modified and adopted for other application because it is designed to perform a specific task. (Educational related application. Medical related application and Scientific application)
- 3. Hardware
Physical component of computer is called Hardware. Examples Monitor, Key-Board, Mouse, Printer etc.
- 4. Firmware
A programs by which perform the predefined instruction in machine memory called firmware. Example ROM, PROM, EPROM etc. ROM, PROM, EPROM
- 5. Humnware
The Human beings which is used the computer called human ware:
- 6. Computer Languages
The functioning of computer is controlled by a set of instruction (called a computer program). These instructions are written to tell the computer.
What operation to perform?
Where to locate data?
How to present results?
When to make certain decisions? And so on.
Communication between tow parties whether they are machines or human being always needs a common language or terminology. The language used in the communication computer instructions in known as the programming language into this language. The computer has its own language and any communication with the computer must be in its language translated into this language.
A language is a system of communication. We communicate to one ano l our ideas and emotions by means of language. Similarly, a computer language ij a mean of communication which is used to communicate between language machine (Computer). Using some computer language a programmer cab still computer what he wants to do. Computer languages divide in three parts;
- Machine languages (low level languages)
- Assembly (or symbolic) language and
- High level languages
- Machine Language
6.1 Machine Language
Computer are made of two-state electronic components which vu,, understand only pulse and no-pulse (or ‘1’ and ‘0’) conditions. Therefore, all instructions and data should be written using binary codes 1 and 0.The binary code is called the machine code or machine language.
Computer do not understand English, Hindi or Tamil. They respond only to machine language. Added to this, computers are not identical in design. Therefore, each computer has its own machine language. (However, the script, 1and 0, is the same for all computers.) This poses two problems for the user.
First, it is a traumatic experience to understand and remember the various combinations of 1’s and 0’s representing number our data and instructions. Also (writing error –free instructions is a slow process.
Secondly, since every machine has its own machine language, the user cannot communicate with other computer (if he does not know its language). Imagine a Tamilian making his first trip to Delhi. He would face enormous obstacles as soon as he moved out for shopping. A language brief would prevent him from communication.
6.2 Assembly Language
An assembly language uses numeric codes rather than numeric codes (as used in machine language). For example, ADD or A is used as a symbolic operation code to represe4nmt addition and SUB or S is used for subtraction, Memory locations containing data are given names such as TOTAL, MARKS, TIME, MONTH etc.
As the computer understands only machine-code instructions, a program written in assembly language must be translated into machine language before the program is executed. This translation is done by a computer program referred to as an assembler.
The assembly language is again a machine- oriented language and hence the program has to be different for different machines. The programmer should remember machine characteristics when he prepares a program. Writing a program in assembly language is still a show and tedious task.
These languages consist of a set of wards and symbols and one can writ program using these in conjunction wit certain rules like ‘English’ language. These languages are oriented toward the problem to be solved or procedures for solution rather than mere computer instructions. These are more user-centered than the machine-centered languages. They are better known as high level languages.
The most important characteristic of a high level language is that it is machine independent and a program written a high level language can be run on commuters of different makes with little or no modification. The programs are to be translated into equivalent machine machine- code instructions before actual implementations.
A program written in a high level language is known as the source program and can be run on different machines using different translations. The translated program is called the object program. The major disadvantage of high level language is that they extra time for conversion and thus they are less efficient compared to the machine-code languages. Figure (4.1) shows the system of implementing the three levels of languages.
Advantage of High Level Language
High Level Language offers many advantages over assembly and machine language.
- High level language are easier to learn, as they use familiar English like terms and follow arithmetic rules.
- They are easier to write, correct and modify. The users need not to know the computer architecture.
- These languages are procedural and problem oriented.
- The programs are portable i.e. they are not machine dependent.
- Programs are simple and readable and much easier of maintenance compared to low level languages.
- 1. ADA :
A high-level programming language developed in the late 1970’s and early 1980’s for the UNITED State Defense Department .Ada was designed to be a general-purpose language for everything from business application to rocket guidance systems. One of its principal features is that is that it supports real- time applications.
- 2. BASIC:
Basic was first invented by professors J.G.Kemeny and T£. Kurtz of Dartmouth College. New Hampshire. U.S.A. as a language for beginners and was implemented in 1964. Since then. Basic has undergone many modifications and improvements and, now, many versions of Basic are available. Recently and attempt has been made to standardize BASIC for universal acceptance. Although BASIC stands for Beginner’s All-purpose Symbolic Instruction Code, it is an extr4ememly powerful and useful language.
SUMMARY OF COMMON HIGH LEVEL LANGUAGE
Year | Language | Name Version | Developed by
Derived from |
Application | Latest |
1957 | FORTRAN | Formula
Translation |
IBM | Science
TRAN 77 Engineering |
FOR |
1958 | ALGOL
ALOGL 68 Engineering |
Algorithmic | International
Language |
Science
Group |
|
1959 | LISP | List Processing
Intelligence |
MIT, USA | Artifical | LISP 1.6 |
1960 | APL | A Programming
Language |
IBM | Science
Engineering |
APLSV |
1961 | COBOL | Common
Business Oriented Language |
Defense Dept.
(USA) |
Business | Cobol 85 |
1964 | BASIC | Beginner All
Standard Basic Purpose Symbolic Instruction Code |
Dartmouth
college |
Engineering
Science Business Education |
|
1965 | PL/1 | Programming
Language Standard |
IBM | General | ANSI
PL/1 |
1970 | Pascal | Blaise Pascal
Institute of Technology |
Federal | General
Pascal |
Standard |
1972 | PROLOG
PROLOG |
Programming
In Logic |
Switzerland’s
University of Marseille |
Artificial
Intelligence |
Standard |
1973 | C | Earlier Language
Called B |
Bell Laboratory | General | ANSI C |
1975 | Ada | Augusta Ada
Byron |
U.S. Defense | General | Ada |
1983 | C++ | C | Bajaarne
Strostrup |
OOP’s | VC ++ |
1995 | Java | Oak | Sun Microsystem | Internet | Java 1.4 |
The Basic language was designed to be conversational right from the start. This can put the programmer or user into direct communication with the computer, usually through a teletype terminal. In this interactive mode, the user cab enter is program statements directly into the computer memory and errors in the statements will be immediately displayed. Thus, the user can correct his mistakes immediately.
While running the program, the programmer cab ask for the results at intermediate points and check for the correctness of his program logic without having to wait for the computer to reach the end of the program.
- 3. FROTRAN:
It is an abbreviation for Formula Translation. It was introduced by IBM in 1957. It is a very useful language or scientific and engineering computations as it contains many functions for complex mathematical operations. It is a compact programming language. Huge libraries of engineerical operations. It is compact programming language. Huge libraries of engineering and scientific programs written in FORTRAN are available to users. In 1977 the American National Standards Institute (ANSI) published a standard for FORTRAN called Fortran 77.50that all manufacturers could use the same form of the language. The latest version is known as FORTRAN 90.
- 4. APL:
It is an abbreviation for A programming Language. It has been developed by IBM. It is a very powerful language. It permits users to define in structions. It contains a large larger system. It can perform complex arithmetic logic operations with a single command.
- 5. C. Language:
A high-level programming language developed by Dennis Ritchie and Brian Kemighan at Bell Labs in the mid 197Although original designed as a systems programming language. C has proved to be a powerful and flexible language that can be used for a variety of application From business programs to engineering. C is a particularly popular language for personal computer programmers because it is relatively small- it requires less memory than other languages.
The first major program written in C was Unix operating system and or many years C was considered to be inextricably linked with UNIX. Now, however, C is a important language independent of UNIX.
- 6. C++
A high-level programming language developed by Bjame Stroustrup at Bell Labs. C++ adds object-oriented features to its predecessor. C. C++ is one of the most popular programming language for graphical application, such as those that run in Windows and Macintosh environments.
- 7. Prolog:
It is suitable language for developing programs nvolvit complex logical operations. It is used primarily for Artifical intelligence applicatic. It was developed in France. The Japanese have chosen this language as a stand language for their fifth generation computer project. It is quite suitable handing large databases and for producing rules-based on mathematical logic.
- 8. LISP:
It stands for LIST Processing. This language was developed IJ McCarthy in the early 1970s. It is suitable for non-number operations involving logic operations. It is used extensively in artificial intelligence and parttem recognition. ^is also used in game playing, theorem proving etc. it is capable for searching, handing and sorting long string or lists of text.
- 9. SNOBOL:
It stands for Sting Oriented Symbolic Language. This language was developed by a group led by Griswold in the mid 1960s. It can manipulate string of characters and hence it is used in text processing. It is capable of performing various types of operations on stings of characters such as combining stings, splitting strings matching strings, etc.
- 10. LOGO:
It was developed by Seymour Paper and his colleagues at MIT in the late 1960s. It has also been popularized as a first educational language that children can use to achieve intellectual growth and problem-solving skills. LOGO has graphics capability. Children can easily use it to make drawings. They can draw colors and animate images. It runs on PCS. It is used to compose music, manipulate text. Manage data, etc.
- 11. APT:
It stands for Automatically Programmed Tooling. It is used in manufacturing applications to control machine tools.
- JAVA:
A high-level programming language developed by Sun Microsystems. Java was originally called OAK, and was designed for handheld devices and setup boxes. Oak was unsuccessful so in 1995 sun changed the name to Java and modified the language in take advantage of the burdening Would Wide Web.
Java is an object-oriented language similar to C++, but simplified to eliminate language features that cause common programming errors. Java source code files) files with a Java extension) are compiled into a format called byte cod (files with i.e.” extension), which can than be executed by a Java interpreter. Compiled Java code; run on most computers because Java interpreters and runtime environments, know… & Java virtual Machines (VMs), exist for most operating systems, including UNIX, DVJ Macintosh OS, and Windows. Byte code can also be converted directly into machine language instructions by a just-in time complier (JIT)
- 7. Language Processor
As we known that computer and understand only machine language or the low level language, which is written in 0’s and 1’s Computer cannot understand. The assembly program and the high-level language program directly. So in Order to run assembly language program, we need translators, which convert these programs into machine codes. Program written in assembly language or High level language are called the source program is called the object program.
- 1. Assembler
Assembler is translator program that translates an assembly language program into machine language program. The assembler is a system program, which is supplied by the computer manufacture. It is written by the system programmers.
- 2. compilers
a compiler is also a translating program that translates the instructions of a high level language into machine language. A compiler can translate only those source programs, which have been written in the language for which the computer is meant. For example- a COBOL program can be translated, only using COBOL compiler.
- 3. Interpreter
an interpreter is another type of translating high-level language into machine code. The difference between compiler and Interpreters in that the complier converts whole high-level language programs into machine language at a time. But interpreters takes one statement of high level language and translates in into a machine code, which immediately exacted.
- 4. Linker and Loader
Machine code (object program) is created by assembly or complier. Languages processors need to be loaded at appropriate place in the memory for execution. The loader is a system program by which perform desired function of loading and links is also another type of system program that perform the task of linking separately compiled function together into one program. Linker is an executable program.
- 8. Program Execution Modes
The execution of a program can be done in one of the following modes depending upon the computer system available and task.
- Batch mode
- On-line mode
- Time-Sharing mode
8.1 Batch mode
in this mode, programs are presented to the system in batches. The system executes them one alter another. All the data required for a particular program are gathered and supplier together with the program. Some applications, such as payrolls, are processed in this mode.
8.2 On-line mode
in this mode, computer executes the program instructions as and when the data is entered into the system. This requires two things.
(i) The program that is used to process the data should reside in the internal emory continuously, and
(ii) The computer system should be on-line
This mode of operation is suitable for applications, such as inventory control, air line reservations, banking system, etc, where the transactions are to be processed as soon as they occur.
8.3 Time Sharing Mode
The time-sharing mode refers to the use of a single computer system by many user in turn. In this mode of operation, each user has one (or more) A input/output device (called terminal) connected to the computer. The most common terminal device is the visual display unit (VDU). The user can enter his program and data at his own terminal and get the processed results either at his terminal or on a printer that is connected to the computer. Although many users share the computer, a user feels that the computer is attending to him all the time.
- 9. Operating System
The software that manages the resources of a computer system am schedules its operation is called the operating system. The operating system act as an interface between the hardware and the user programs and facilities the execution of the programs.
The principal functions of operating system include:
(1) To control and coordinates of peripheral devices such as printers, display screen and disk device
(2) To monitor the use of the machine’s resources.
(3) To help the application programs execute its instructions.
(4) To help the user develop programs.
(5) To deal with any faults that may occur in the computer and inform the operator.
The operating system is usually available with hardware manufactures and is rarely developed in-house owing to its technical complexity. Small computers are built from a wide variety of micro- processor chips and use different operating systems. Hence, an operating system runs on one computer may not run on the other.
The most popular operating system for an 8-bit microprocessor is CP/M (Control Program for Microprocessors). It enjoys immense popularity and is offered by many manufactures. It has, therefore, stimulated the development of an abundance of software packages that are CP/M compatible.
Recently, with the introduction of 16/32-bit processors, operating systems such as MS-DOS, UNIX and CP/M-86 are becoming popular. The operating system limits the variety and nature of devices which can be attached to the computer and kind of software which can be supported.
- 10. Application of O.S
O.S. is a master program for all programs O.S. It has following functions.
(I) Process Management
A process is the unit of work in a system. Such a system consists of a collection of process, some of which are o.s. process (those that execute system code) and the rest of which are user process (those. That executes user code). All these process can potentially execute concurrently by multiplexing the CPU among them. The O.S. is responsible for the following activities in connection with process management.
(i) Creating and deleting both user and system process.
(ii) Suspending and resuming process.
(iii) Providing mechanism for process synchronization.
(iv) Providing mechanism for process communication.
(v) Providing mechanism for deadlock handling main.
(II) Memory Management
Main memory is a repository of quickly accessible data shared by the and I/O devices. The O.S. is responsible for the following activities in connect with Memory Management.
(i) Keeping track of which parts of memory are currently being used and by whom.
(ii) Deciding which processes are to be loaded into memory when memory space becomes available.
(iii) Allocating and deallocating memory space as needed.
(III) File Management
A File is a collection of related information defined by its creator commonly fill represent program 9both source and object forms) and data.
The O.S. is responsible for the following activates in connection with file management.
(i) Creating and deleting files.
(ii) Creating and deleting directories.
(iii) Supporting primitives for manipulating file, and directories.
(iv) Mapping files onto secondary storage.
(v) Backing up files on stable (Nonvolatile) storage media.
(IV) I/O System Management
One of the purpose of an operating system is to hide the peculiarities of specific h/w devices from the user. For Example: in UNIX. The peculiarities of I/O devices are hidden from the bulk of the O.S.
(V) Secondary Strong Management
Main memory to small to accommodate all data and programs, and because the data that it holds when power is lost the computer system must provide secondary storage to back up main memory. The O.S. is responsible for the following activities in connection with disk management.
(i) Free space management
(ii) Storage allocation.
(iii) Disk scheduling
(VI) Protection
O.S. also provide security to data protection involves ensuring that all access to system resources is controlled. Security of the system from outsiders is also important such security starts with each user having to authenticate him self or herself to the system usually by means of a password. To be allowed access to the resources.
(VII) Communication
O.S. provide the facility of communication in which one process need to exchange information with another process there are tow ways for such communication : first take place between processing execution o same Computer systems, the second take place between network.
(VIII) Error Detection
The O.S. system constantly needs to be aware of possible error. Errors may occur in the CPU and memory H/w such as power failure or memory error). In I/O devices or in the user program.
(IX) Resource Allocation
when there are multiple user or multiple jobs running at the same time resources must be allocation to each of them. Many different types of resources are managed by the O.S. some such as CPU cycles, main memory, and file storage may have special allocation code. Where as others such as I/O devices may have much more general request and release code.
- 11. Types of O.S.O.S
The type of Operating System.
- Batch O.S.
- Multiprogramming
- Network O.S.
- distributed O.S.
(I) Batch O.S
A Batch Operating System work as per their name. all Execution performs in batch mode. The process of job execution is called spooling (Simultaneous Peripheral Operation On Line). In spooling, the system accepts jobs and places them in a queue to wait execution. All jobs are placed in a queue on a disk unit. The Batch job may be executed on a serial basis as per the priority decided by the operating system.
(II) Multiprogramming O.S.
Multiprogramming Operating System called concurrent processing O.S. it is the capability of CPU to execute to are more programs concurrently. This two or more programs are stored concurrently in primary storage and CPU moves. From one program to another and execute them partially in turn.
Multiprogramming O.S. compared to batch O.S. are fairly sophisticated. This operating system is sophisticated as compare to batch operating system Multiprogramming has a significant potential for improving system throughput and resource utilization with very minor differences.
Different forms of multiprogramming O.S. are :
1 Multi Tasking O.S.
2 Multi Processor O.S.
3 Multi- User O.S.
(1) Multi Tasking O.S
It is allows running one of the many programs stored in main memory using the CPU without in any way. The disturbing the individual programs. Since the human response as user of computer is much slower than the speed of computer. This O.S. in CPU give the feeding that it is running many program on same time.
It is thus to allow a user to run more than one program concurrently MS Windows (any version) and IBM’s OS/2 are such system. Example of a function while editing a document in the foreground a printing job can be given in the background. The status of each program can be seen on the screen by partitioning it into a number of windows. The progress of program can be viewed in the window of each.
Fig. Multi Tasking
(2) Multi Processor O.S.
In a multiprocessor o.s many processor are controlled by one o.s. The multiprocessing capabilities are used in highly sophisticated and advanced computer system where there are more than one CPU to execute totally exclusive Process at the same time. This is not same as normal multiprogramming where one CPU is shared by several programs. It give more improve through put.
Example – Multiprocessor operation can be found in some advanced PC’s and in real time system.
Fig. A Multiprocessing System
(3) Multi-User System
It is allow many users to work on the same computer at the same time using different terminals. Although frequently referred as multiprogramming, multiu.v. systems do not imply multiprogramming or multi tasking. Multi-user o.s. minimizes the idle time of a computer terminal available to him. He can inti ate a program from his terminal and interact with it during its execution. ‘He has complex access to computer’s resources.
The Operating system of the computer assigns each user a portion of primary memory and divides the computers time among the different users. The Computer does a small amount of job for one user, and then does a small amount of job for the next user and so forth. Since the computer operates so quickly, each user feels that the system is working for him alone.
Fig. A Multiprocessing System
Examples: UNIX is a multi-user, multi programmed; time-shared o.s. in individual users o UNIX can execute several processes at the same time. A dedicated transition processing system such as railway reservation system like dedicated system that supports hundred of terminal under control of single program is an example of multi-user Operating System
(III) Network O.S.
A Network o.s. is a collection of S/W and associated protocols that allow a set of autonomous computer. Which are interconnected by computer network to be used together in a convenient and cost effective manner? In network o.s. the users are aware of existence of multiple computers and can long in to remote machines and cop files from. One machine to another machine.
(IV) Distributed O.S.
A distributed o.s. is one these looks to its. User like an ordinary centralized o.s. but runs on multiple independent C.P.U In other words user views the system as virtual unprocessed. But not as a collection of distinct machines. In a true distributed system, users are not aware of where their programs are being run or where their files are residing.
- 12. Example of Operating System
(i) MVS (OS/360)
OS/360 was mainly designee for mainframe computers by IBM in 1966 and as a family of computers and spanning the complete range from small business machines to large scientific computers and spanning the complete range from small business machines to large scientific machines only one set of s/w would be needed for these system which all used. The same operating system. This arrangement was supposed to reduce the maintenance. Problems for IBM and to allow users to move program and application freely form one IBM system to another. Unfortunately, OS/360 tried to be all things for all people. As a result it did none of its tasks. Especially well.
(ii) Unix
Unix operating system designed by at & T bell laboratories (USA) in 1969. It is multi-user, multitasking-operating system i.e. multiple uses computer III operates simultaneously and they may have different task. It is machined independent operating system.
The Unix has as following uniqueness features:
Multitasking capability.
Multi-user capability.
Portability.
Unix Programs.
Library of application S/W
Unix has following main components
1. Kernel 2. Shell 3. Tools and application
Fig. Unix Operating System
- The Kernel, which schedules task and manages storage.
- The Shell, which connects and interprets user’s commands, call programs from multi-user and executes them.
- the tools and application that offer additional functionality to the operating system.
(iii) Linux
Linux is a marden free operating system based on Unix standard. It has been designed to run efficiently and reliably on common PC H/W. it also run on a variety of other platforms. It provides programming interface and larger interface compatible with standard Unix system. And can run large number protection between processes and running multiple processes according to a time sharing scheduler.
Components of Linux system are as follows –
1. Kernel
2. System Libraries.
3. System Utilities.
(iv) Kernel
The Kernel is responsible for maintaining all the imp0ortant abstraction of the operating system, including such things as virtual memory and process.
(v) System Libraries
The System libraries define a standard set of functions through which applications can interact with the Kernel, and that implement much of the operating system functionality that does not need the full privileges of kernel coed.
(vi) System Utilities
The System utilities are program that perform individual, specialized management tasks. Some system utilities may be invoked just once to initialize and configure some aspect of the system others known as demons in UNIX terminology may run permanently, handling such tasks as responding to incoming network connection accepting logon requests from terminals or updating log files.
(vii) Windows 98
Windows 98 is a truly easy graphical interface that makes. It dramatically simpler to use Your PC. You can install modems, CDROM, Drives and other peripherals. It is a multitasking operating system i.e. you can open multiple. S/W at time. It ca run your current ms-dos. Based program in a more stable environment it is also offer enhance multimedia more powerful mobile features and integr4ated and seamless networking.
(viii) Mach O.S.
The Mach operating system traces its ancestry to. The accent operating system developed at Carnegie Mellon university CMU in 1981 mach’s communication system and philosophy an driven from accent but many other significant portion of the system (for example the virtual memory system, task and thread management) were developed from scratch mach o.s id graphic oriented mouse oriented user interface made personal computing much friendlier and or more convenient
The mach operating system was designed with the following three critical goals in mind:
- Emulate 4.3 bsd Unix so that the executable files from can run correcting under mach.
- Be a modem operating system. That support many memory models and parallel and distributed computing.
- Have a kernel that is simpler and easier to modify than 4.3 BSD.
(ix) MS-DOS(Microsoft Disk Operating System)
MS-DOS (Microsoft Disk Operating System) Developed by the Microsoft computer using by 8086/8088 INTEL processor for personal computer.
DOS provide the method to store information, application/system Program and coordinate the computer system. DOS instruct to computer how to read data which is store in your disk. It is also locate the information on disk or memory and control the other devices.
The previous version of DOS much simple. Slowly-slowly the new version become complex. These DOS is 16-bit operating system. It doesn’t support multiuser or multitasking.
(x) Windows NT/2000
Microsoft designed windows 2000 to be an extensible, portable operating system windows 2000 supports multiple operating environment and symmetric. Multiprocessing. Enable windows 2000 to support a wide variety of application environment for instance windows 2000 can run pro0gram complied for ms-dos win 16 windows 95. It provides virtual memory interpreted cashing and preempting scheduling windows 2000 supports a security model stronger then those of previous Microsoft operating system and includes inter unitizations features. Windows 2000 run on wide variety of computers, so user can choose and upgrade H/W to match, their budgets and performance requirement, without needing to alter the application that they run.