computer notes.

           
Computer Software and Programming  Languages

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An information system has five parts. People, procedures, software, hardware and data. Software which is one of the most important part of an information system. Is an other name for a program or programs. Program is the step by step instructions that tell the computer how to do its work. The purpose of a software is to convert data (unprocessed facts) into information (processed facts). In most cases, words software and programs and interchangeable.

There are two major kinds of software-application software and system software.

Application software are the software the users of the computer use. Whereas system software are used by the computers. 


Application Software
Application software may be describe as end-user software. They perform useful work on general-purpose tasks such as word processing and cost estimating.

Application software may be

1. Packaged

2. Custom Made


1. Packaged Software
Packaged Software are the programs prewritten by professional programmers that are typically offered for sale.


2. Custom-Made Software
Custom-Made or Custom programs are the programs written for a specific purpose and for a specific organization. Using computer languages, programmers create this software to instruct the company's computer to perform whatever tasks the organization wants.

There are certain general purpose programs which are called "basic applications" The most popular basic tools are


Word Processing Programs used to prepare written document.

Spreadsheets Programs used to analyse and summarize numerical data.

Database Manageers used to organize and manage data and information.

Presentation Graphic Programswhich are used to communicate a message.

Personal Information Management Programs used to organize and schedule activities.

Integrate Programs which combine some or all of these applications in one program.


Summary of Basic Application Software

The summary of the basic application software mentioned above has been given below. Which shows various software designed by well known software publishers. Microsoft, Lotus and Corel.


Basic Applications

Word Processors = Microsoft Word, Lotus, Word Pro, Corel WordPerfect

Spreadsheets = Microsoft Excel, Corel Quattro Pro, Lotus-2-3

Database Managers = Microsoft Access, Corel Paradox, Lotus Approach

Presentation Graphics = Microsoft PowerPoint, Corel Presentation

Personal Information managers Microsoft Outlook, Lotus Organizer

Integrated Packages = Microsoft Work, Lotus Works.

Software Suites = Microsoft Office 97, Corel Office 97


Common Features of Basic Application
As all the above mentioned categories of software are designed to be used by many people to perform most common kinds of tasks we call them basic applications. Most common application software have some common features. The most important of them are given below.


Menu
Almost all software packages have menus to present commands. Typically menus displayed in a menu bar at the top of the screen when one of the item is selected a pull down menu appears.

This is a list of commands associated with the selected menu.


Shortcut keys

Many applications also have shortcut keys for frequently used commands. Many of the shortcut keys are function keys. F1, F2 and so on. Others shortcut use key combinations typically consisting of the Alt, Ctrl or Shift key used in combination with a letter number or function key. For example in Word97 the short cut key F7 starts the spelling tools and the key combinations of shift and F7 starts the Thesaurus tools.


Toolbars
Toolbars are typically below the menu bar. They contain icons or graphic representations for commonly for commonly used commands.


Help

For most applications packages one of the menus on the menu bar is Help. This typically include a table of contents a search feature to locate reference information about specific commands and access to specific learning features such as tutorials and step-by-step instructions.


Dialog Boxes

Dialog boxes frequently appear after selecting a command from a pull down menu. These boxes are used to specify additional options.


Scroll Bars
Scroll bars are usually located on the right and / or the bottom of the screen. They enable user to display additional information not currently visible on the screen.


Edit

The ability to change or edit entries is a feature common to almost all applications. The edit feature makes revising and updating easy and is one of the most valuable features.


Save and Print
Common to all applications software is the ability to save or store your work as a file on a floppy or hard disk. This allows user to open and use the file at a later time in case user wants to add or modify the document. In addition all applications allow user to a copy of his document on paper.

Word processing programs and spreadsheets program are most commonly used categories of application software hence we explain them in much more detail.


Word Processors
word processing software creates text-based documents such as letter, memos, term papers and reports. Once it was thought that only secretaries would use word processors. Now they are used extensively in managerial and professional life. Indeed, it has been found that among the basic software applications. Word processors are most important software used by common people.

Popular word processing packages include Microsoft Word. Corel WordPerfect and Lotus Word Pro as shown in the above summary of basic applications.


Important Features of Word Processors

Some important features shared by most word processors are as follows


Word Wrap and the Enter Key
One basic word processing feature is word wrap i.e. word processor automatically moves the insertion point to the next line once the current line is full. The begin a new paragraph or to leave a blank line Enter key is pressed.


Spelling and Grammar Checkers
Many word processors include a spelling checker feature that identifies typing errors. For example Word97 identifies misspelled words with a red wavy underline. Similarly grammar checkers can be run that will identify poor wording excessively long sentences and incorrect grammar.

Alignment

Text can be aligned within the margin in various way. The most common alignment is left alignment.


Formatting

Text can be enhanced in a variety of ways including adding basics formatting such as bold, under line and italics.

Besides above mentioned feature other common features of word processors are References, Search and Replace, Tables, Hyperlinks, Thesaurus, Graphics, Internet publishing and Workgroup.


Spreadsheets

Spreadsheets is an electronic worksheet used to organize and manipulate and display option for "what-if" analysis. Spreadsheets are used by financial analysts, accountants, contractors and other concerned with manipulating numeric data.

Popular spreadsheets packages include Microsoft Excel, Quattro Pro and Lotus 1-2-3 as shown by above summary.


Common feature of Spreadsheets

Like the word processors, spreadsheets designed by various software publishers share following common features.


Formulas and Functions
Formulas are the instructions for calculations. They calculate result using the numbers in reference cells. Whereas functions are prewritten formulas that perform calculations automatically.


Analysis

The recalculation feature can be used to analyze the effect of changes to the spreadsheets.


Analytical Graphs
To help visualize the data in spreadsheets user can create analytical graphs or charts.


Workgroup
One of the newest additions to spreadsheets applications is the workgroup program which allows multiple users to collaborate electromically on spreadsheet.


Linked Files
Most spreadsheets programs allow users to link cells in one worksheet file to cells in other worksheets in the same file or to other worksheet files. Whenever a charge occurs in one file the linked cells in the other worksheets are automatically updated.


Advanced Application Programs
Besides above mentioned basic application programs there are certain programs which are called "advanced applications". These are more specialized than the basic application. These programs are widely used in certain career areas. The most popular tools are:


Graphic Programs used to create professional publications and to capture and edit graphic images.

Multimedia used to integrate all kinds of information including video, audio, graphic and text into a single interactive presentation.

Web Publishers used to create interactive multimedia web page. Project management used to plan projects schedule people and control resources.


System Software
The user interact with the application software whereas system software enables the application software to interact with the computer hardware. System software is a "background" software. It includes programs that help the computer manage its internal resources.

Kinds of System Software

System software deals with the physical complexities of how the hardware works. System software consists of the following four programs.

1. Bootstrap loader

2. Diagnostic routines

3. Basic input-output system

4. Operating System

1. Bootstrap loader

The bootstrap loader is a program that is stored permanently in the computer's electronic circuitry. When computer is turned on the bootstrap loader obtains the operating system from hard disk and loads it into memory. This is called booting the system.

2.Diagnostic Routines

These are also programs stored in the computer's electronic circuitry. They start up when machine is turned on. They test the primary memory the central processing unit and other parts of the computer. Their purpose is to make sure the computer is running properly.

3. Basic Input-Output System

It consists of service programs stored in primary storage. These programs enable the computer to interpret keyboard characters and transmit them to monitor or to a floppy disk.

4.Operating System

The operating system is a collection of programs that help the computer to manage its resources. The Operating System takes care of lot of internal matters. For example it interprets the commands user gives to run programs. It manages memory data and file.

The most important system program is the operating system which interacts between the application software and the computer. The operating system handles such details as running (executing) programs, storing data and programs and processing data.

Microcomputer operating systems change as the machines themselves become more powerful and outgrow the older operating systems.

The most popular microcomputer operating systems are

DOS the original operating system for International Business Machines (IBM) and IBM compatible microcomputers.

Windows not an operating system but an environment that extends the capability of DOS.

Windows 95 a widely used operating system with the built-in internet support.

Windows 98 a new operating system with the intensive internet and multimedia support.

Windows NT a powerful operating system designed for powerful microcomputers.

OS/2 Warp the operating system developed by IBM for powerful microcomputers.

Macintosh Operating System the standard operating system for Apple Corporation's Macintosh computers.

Unix an operating system originally developed for microcomputers that can run on many of the powerful microcomputers.

Disk Operating System

DOS's original developer Microsoft Corporation sells it under the name MS-DOS. It was originally standard operating system for all microcomputers which were IBM compatible or DOS based.


Advantages

1. Even today DOS is still widely used operating system.

2. An enormous number of application programs have been written for DOS. Indeed more specialized software is available for DOS for than any other operating system.

3. DOS runs on many computers, old and new that are cheap.

Disadvantages

1. It can support very limited primary storage.

2. It can be used only for single-tasking and not for multi-tasking.

3. It uses character-based interface.

Windows 98

Windows like Windows 95, Window 98 and Windows NT is not a operating system, rather an operating environment. While Windows 95, Windows 98 and Window NT are operating systems. But Windows 98 is one of the most popular operating systems being used nowadays. It is an advanced version, designed for today's very powerful microcomputers.

Advantages

1. It is faster in many common tasks like starting up loading applications and shutting down. It includes a Tune-up wizard automatically monitors system operation and suggest ways to improve performance.

2. Windows 98 is fully integrated with Microsoft's browser, Internet Explorer, making Internet access easier and faster.

3. Plug and play capability is extended to support the newest advance in technology. Multiple views of an application or multiple applications can be viewed on separate monitors simultaneously.

4. Windows 98 has advanced audio and video capability. With a tuner card, TV on microcomputers monitor can be watched.

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Disadvantages

1. Windows 98 requires at least a Pentium Microprocessor to operate effectively. Besides more hard disk space and memory are necassary.

2. Fewer applications have been written specifically for it. It can however run most DOS, Windows and Windows 95 applications.

COMPUTER LANGUAGE

Language is a system for representation and communication of information or data. Like human beings, a language or signal is required to communicate between two persons. Similarly, we cannot obtain any result by computer without langtage. Computer does not understand directly what we are communicating with computer as English or Arabic, it understands only machine language (binary codes 0-1). Computer translates English language into machine codes through interpreter then process instructions and give us the results.

The computer languages can be divided into two main levels.

* Machine language (0-1) 

* Symbolic language (A-Z) 

Symbolic languages are further divide into two main levels

* High-level language 

* Low-level language 

MACHINE LANGUAGE

Although computers can be programmed to understand many different computer language. There is only one language understood by the computer without using a translation program. This language is called the machine language or the machine codes. Machine codes are the fundamental language of the computer and is normally written as strings of binary 0-1.


ADVANTAGES AND LIMITATIONS OF MACHINE LANGUAGE
Programs written in machine language can be executed very fast by the computer. This is mainly because machine instructions are directly understood by the CPU and no translation of program is required.

However, writing a program in machine language has several disadvantage.

MACHINE DEPENDENT

Because the internal design of every type of computer is different from every other type of computer and needs different electrical signals to operate. The machine language also is different from computer to computer.

DIFFICULT TO PROGRAM

Although easily used by the computer, machine language is difficult to program. It is necessary for the programmer either to memorize the dozens of code number for the commands in the machine’s instruction set or to constantly refer to a reference card.

DIFFICULT TO MODIFY

It is difficult to correct or modify machine language programs. Checking machine instructions to locate errors is difficult as writing them initially.

In short, writing a program in machine language is so difficult and time consuming.

SYMBOLIC LANGUAGES

In symbolic languages, alphabets are used (a-z). symbolic languages are further divide into two main levels.

* High level languages 

* Low level languages 

LOW LEVEL LANGUAGE

A language which is one step higher than machine language in human readability is called Assembly Language or a low-level language. In an assembly language binary numbers are replaced by human readable symbols called mnemonics. Thus a low-level language is better in understanding than a machine language for humans and almost has the same efficiency as machine language for computer operation. An assembly language is a combination of mnemonic, operation codes and symbolic codes for addresses. Each computer uses and has a mnemonic code for each instruction, which may vary from computer to computer. Some of the commonly used codes are given in the following table.
COMMAND NAMEMNEMONIC

Add - ADD

Subtract - SUB

Multiply - MUL

Compare Registry - CR

Compare - COMP

Branch Condition -BC

Code Register -LR

Move Characters -MVE

Store Characters -STC

Store Accumulator - STA

An assembly language is very efficient but it is difficult to work with and it requires good skills for programming. A program written in an assembly language is translated into a machine language before execution. A computer program which translates any assembly language into its equivalent machine code is known as an assembler.

HIGH – LEVEL LANGUAGE

A language is one step higher than low-level languages in human readability is called high-level language. High – level languages are easy to understand. They are also called English oriented languages in which instruction are given using words. Such as add, subtract, input, print, etc. high level language are very easy for programming, programmer prefer them for software designing that’s why these languages are also called user’s friendly languages. Every high level language must be converted into machine language before execution, therefore every high level language has its own separate translating program called compiler or interpreter. That’s why some time these languages are called compiler langauges. COBOL, BASIC, PASCAL, RPG, FORTRAN are some high level languages.

INTERPRETER

An interpreter is a set of programs which translates the high-level language into machine acceptable form. The interpreters are slow in speed as compared to compilers. The interpreter takes a single line of the source code, translates that line into object code and carries it out immediately. The process is repeated line by line until the whole program has been translated and run. If the program loops back to earlier statements, they will be translated afresh each time round. This means that both the source program and the interpreter must remain in the main memory together which may limit the space available for data. Perhaps the biggest drawback of an interpreter is the time it takes to translate and run a program including all the repetition which can be involved.

Compiler

A compiler converts the programmer's procedural language program called the source code into a machine language code which is called the object code. This object code can then be saved and run later. Example of precedural languages using compilers are standard versions of Pascal, COBOL, and FORTAN.


Pascal

Another language that is widely used on microcomputers and easy to learn is Pascal, named after Blaise Pascal, a French mathematician. This language has become quite popular in computer science educational programs.


C/C++
C is general purpose language that also works well with microcomputers. It is useful for writing operating systems, spreadsheets programs, database programs and some scientific applications. C++ is a version of C that incorporates object-oriented technologies.


COBOL

COBOL which stands for Common Business-Oriented Language is one of the most frequently used programming languages in business. Through harder to learn than BASIC its logic is easier to understand for a person who is not a trained programer.


FORTRAN

Short for FORmula TRANslation, FORTRAN is a widely used scientific and mathematical language. It is very useful for processing complex formulas. That's why many scientific and engineering programs have been written in this language.

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