1 Chapter 8 Computer Software. 2 What Types of Software Make a Computer Useful?

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Chapter 8Computer Software

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What Types of Software Make a Computer

Useful?

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Objectives1. Understand the scope of knowledge needed to

interact effectively with a computer.

2. Understand the two basic types of software used in the operation of a computer.

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Interactive With the System To interact effectively with a computer, user needs to

be knowledgeable in four areas:

1. General software concepts (for example, windows, menus, uploading, and so on).

2. The operation and use of the hardware over which you have control (such as the PC, magnetic disk, and printer).

3. The function and use of the computer's operating system and/or its graphical user interface (GUI), both of which provide a link between the user, the computer system, and the various applications.

4. The specific applications programs you are using.

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Interactive With the System (continued)

The first three areas are prerequisites to the fourth because you will need a

working knowledge of software concepts,

hardware, and

the operating system and/or a GUI

before you can make effective use of

Quicken (accounting), Harvard Graphics (presentation graphics), Paradox (database).

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Categories of Software

Computer hardware cannot perform alone.

Software refers to the instructions that direct the operations of a computer.

There are two basic types of software:

system software (controls hardware)

application software (performs specific tasks).

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Categories of Software(continued)

System software tells the computer how to operate.

System software is a collection of programs that starts the computer and coordinates all the activities of the computer system.

It does not accomplish specific tasks for a user, such as creating documents or analyzing data.

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System software includes

Operating systems (the most important type of system software),

Data management software, Computer language-oriented software, and Utilities that help users perform various functions.

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A principal component of system software is the operating system.

Data management software includes

database and file management programs that manage data for an operating system.

Computer language-oriented software includes

language translators such as assemblers, interpreters, and compilers .

program generators (programs that automatically generate program code), debugging and testing programs.

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Utilities are programs that are purchased as separate products; they perform a wide range of functions. This type of software includes products such as

data conversion programs that convert data from one format to another,

data recovery programs that restore damaged or accidentally erased data,

librarians that log and track the locations of disk or tape program files,

security and auditing programs, and merge and sort programs.

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Application software refers to programs that allow you to accomplish specific tasks, like creating a document, organizing data, or drawing graphs.

Software acts as a connection, or interface, between you and the hardware.

Interface is a term that describes how two parts are joined so that they can work together.

System software and application software provide an interface to the hardware.

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Figure 8.1 shows the functional relationship among system software, application software, hardware, and a user.

UserUser

System softwareSystem software

HardwareHardware

Application software

Application software

Figure 8.1 The Relationship Among System Software, Application Software, Hardware, and a User

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Operating System

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Objectives Define operating system, describe the

major functions, and discuss several ways it is typically used in the day-to-day operation of a computer.

Describe several capabilities of operating systems. Contrast three types of user interfaces. Describe the characteristics and functionality of a

graphical user interface (GUI). Understand the purpose of a disk operating system and

an operating environment, and identify four major microcomputer operating systems and their associated environments.

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What Is an Operating System? An operating system layer,

designed to be invisible to the user, lays between the application software and hardware.

An operating system (OS) is a core set of programs that control and supervise the hardware resources of a computer and provide services to other system software, application software, programmers, and users of a computer.

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What Is an Operating System? (continued)

The OS gives the computer the instructions it needs to operate, telling it how to interact with hardware, other software, and the user.

The OS establishes a standard interface, or means of communication, between users and their computer systems.

When you power up a computer, you boot the system.

The booting procedure is so named because the computer "pulls itself up by its own bootstraps" (without the assistance of humans).

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What Is an Operating System? (continued)

When booting the system,

First, a program in read-only memory (ROM) initializes the system and runs a system check to verify that the electronic components are operational and readies the computer for processing.

Next, the operating system is loaded to RAM, takes control of the system, and presents the user with a system prompt or a GUI screen full of options.

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Operating System Parts

Operating systems are composed of two major parts:

control programs

service programs

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Operating System Parts (continued)

Control programs manage computer hardware and resources.

The main program in most operating systems is the supervisor program.

A supervisor program is a control program that is known in some operating systems as the monitor, executive, or kernel.

The supervisor program is responsible for controlling all other OS programs as well as other system and application programs.

The supervisor program controls the activities of all of the hardware components of a computer.

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Operating System Parts (continued)

Service programs are external OS programs that provides a service to the user or programmer of a computer.

They must be loaded separately because they are not automatically loaded when the operating system is loaded.

They perform routine but essential functions, such as formatting a disk for use and copying files from one location to another.

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Operating System Functions

In order to meet the dual requirements of providing support for common computer system tasks and hardware independence, operating systems perform these four important functions:

· Manage the allocation of main memory· Coordinate processing tasks· Schedule the use of peripheral devices, such as secondary

storage devices and printers· Monitor the use of all equipment

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Managing Memory

Memory management includes protecting programs in memory from accidental erasure and accommodating programs that exceed the physical limitations of main memory.

An OS (operating system) keeps track of its own location and how much main memory it occupies and prohibits other programs and data from being stored in its space.

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Coordinating Processing Tasks A job is a computerized task.

• A job is a collection of one or more related programs and their data.

• Each job requires use of the processor, main memory, and secondary storage devices.

Many modern operating systems make it possible to schedule a job for processing based on it’s priority and it’s computer systems resource requirements.

In the mainframe computer environment, each job to be processed includes a group of instructions written in a special language called job control language (JCL).

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Large Computer Systems

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Managing Resources

Operating systems manage computer resources by:

· Keeping track of computer access and usage· Keeping track of peripheral device usage· Providing up-to-date reports of system utilization costs

Access to and usage of a computer system can be monitored (through the use of a run log) for security and control - to prevent unauthorized access to, and use of, a computer system and user files.

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Typical Day-to-Day Uses of an Operating System

Executing application programs.

Formatting floppy diskettes.

Setting up directories to organize your files.

Displaying a list of files stored on a particular disk.

Verifying that there is enough room on a disk to save a file.

Protecting and backing up your files by copying them to other disks for safekeeping.

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Typical Day-to-Day Uses of an Operating System (continued)

Computer housekeeping operations such as erasing old files that are no longer needed, moving files from one directory to another for better organization, and renaming files to make their content more evident.

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How Do Operating Systems Differ?

Operating systems for large computers are more complex and sophisticated than those for microcomputers because the operating systems for large computers must address the needs of a very large number of users, application programs, and hardware devices, as well as supply a host of administrative and security features.

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How Do Operating Systems Differ? (continued)

Early computers used serial processing operating systems, which meant the computer was capable of processing only one job at a time.

Modern operating systems allow computer to run two or more programs simultaneously. They are called multiprogramming operating systems. Several techniques are used to accomplish this, including:

• multitasking• time sharing• multiprocessing

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Multitasking Multitasking means that a single

user can run more than one job at a time.

In a multitasking system, main memory is usually partitioned into segments for storing the user programs and their associated data separately.

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Time Sharing Time sharing is a multiprogramming technique that makes

multiple programs appear to run at the same time by allocating short periods of CPU time to each of the programs on a rotating basis.

A major benefit of time sharing is that users with small programs do not have to wait for the CPU to come to a logical stopping point in large, complicated programs.

Under time sharing, no single program is allowed to dominate the CPU’s time.

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Multiprocessing Multiprocessing is possible when a computer system

consists of two or more processors. Multiple processors share the workload of a computer

system

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Operating system capabilities can be described in terms of

the number of users they can accommodate at one time,

how many tasks can be run at one time, and

how they process those tasks.

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Number of Users

A single-user operating system allows only one user at a time to access a computer.

Most operating systems on microcomputers, such as DOS and Window 95, 98, are single-user access systems.

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Number of Users (continued)

A multiuser operating system allows two or more users to access a computer at the same time (UNIX).

The actual number of users depends on the hardware and the OS design.

Time sharing allows many users to access a single computer.

This capability is typically found on large computer operating systems where many users need access at the same time.

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Number of Tasks

A single tasking operating system allows only one program to execute at a time, and the program must finish executing completely before the next program can begin.

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Number of Tasks (continued)

A multitasking operating system allows a single CPU to execute what appears to be more than one program at a time. Several techniques are used to accomplish this, including:

• Context switching• Cooperative multitasking• Time-slice multitasking• Multithreading supports

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Context switching

allows several programs to reside in memory but only one to be active at a time. The active program is said to be in the foreground. The other programs in memory are not active and are said to be in the background. Instead of having to quit a program and load another, you can simply switch the active program in the foreground to the background and bring a program from the background into the foreground with a few keystrokes.

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Cooperative multitasking

in which a background program uses the CPU during idle time of the foreground program. For example, the background program might sort data while the foreground program waits for a keystroke.

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Time-slice multitasking

enables a CPU to switch its attention between the requested tasks of two or more programs. Each task receives the attention of the CPU for a fraction of a second before the CPU moves on to the next. Depending on the application, the order in which tasks receive CPU attention may be determined sequentially (first come first served) or by previously defined priority levels.

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Multithreading supports

several simultaneous tasks within the same application. For example, with only one copy of a database management system in memory, one database file can be sorted while data is simultaneously entered into another database file.

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Number of Processing

Multiprocessing Interprocessing Real-time processing Virtual-machine (VM) processing Virtual memory

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Number of Processing (continued)

Multiprocessing operating system

allows the simultaneous execution of programs by a computer that has two or more CPUs. Each CPU can be either dedicated to one program, or dedicated to specific functions and then used by all programs.

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Interprocessing (dynamic linking)

is a type of processing that allows any change made in one application to be automatically reflected in any related, linked application.

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Real-time processing

allows a computer to control or monitor the performance of other machines and people by responding to input data in a specified amount of time.

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Virtual-machine (VM) processing

creates the illusion that there is more than one physical machine. VM capabilities permit a computer to run numerous operating systems at one time. VM capabilities are typically used on supercomputers and mainframes.

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Virtual memory (virtual storage)

allows you to use a secondary-storage device as an extension of main memory. Virtual memory resolves the problem of insufficient main memory to contain an entire program and its data.

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How Will I Use an Operating System?

The user interface of an operating system is the portion of the program with which users interact.

The user interface can be

Command-line, Menu-driven, and Graphics-based.

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How Will I Use an Operating System? (continued)

A command-line interface requires a user to type the desired response at a prompt using a special command language.

To be an effective user of any command-line software, you must memorize its commands and their exact syntax-no easy task.

A menu-driven interface allows the user to select commands from a list (menu) using the keyboard or a pointing device such as a mouse.

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A graphical user interface (GUI)

The trend is away from text-based, command-line interfaces to user-friendly, graphics-oriented environment called a graphical user interface (GUI).

Graphical user interfaces rely on graphics-based software.

Graphic-based software permits the integration of text with high-resolution graphic image, called icons.

GUI users interact with the operating system and other software packages by using a pointing device and a keyboard to issue commands.

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Rather than enter a command directly, the user chooses from options displayed on the screen.

The equivalent of a syntax-sensitive operating system command is entered by pointing to and choosing one or more options from menu or by pointing to and choosing a graphics image, called an icon.

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typically GUI includes some or all of the following parts:

icons, which are graphical images that represent items, such as files and directories.

a graphical pointer, which is controlled by a pointing device (mouse), to select icons and commands and move on-screen items.

on-screen pull-down menus that appear or disappear, controlled by the pointing device.

windows that enclose applications or objects on the screen.

GUIs have effectively eliminated the need for users to memorize and enter cumbersome commands.

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What Types of Operating Systems and Environments Are Used on Microcomputers?

A disk operating system (DOS) is an operating system that allows and manages the use of disk drives for storing and accessing data and programs.

An operating environment is software that improves its user interface and enhances the functions of an operating system.

Operating environments often use windows to allow the display of several applications on the screen concurrently and to facilitate data transfer between them.

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A disk operating system (DOS) is an operating system that allows and manages the use of disk drives for storing and accessing data and programs.

An operating environment is software that improves its user interface and enhances the functions of an operating system.

Operating environments often use windows to allow the display of several applications on the screen concurrently and to facilitate data transfer between them.

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(continued)

UserUser

HardwareHardware

Applicationsoftware

Applicationsoftware

Operating environment

Operating system

Operating environment

Operating system

The operating environment logically sits on top of the OS (See Figure 8.2).

Figure 8.2 The operating environment is an interface between the user and the operating system

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(continued)

Popular microcomputer operating systems include MS-DOS, OS/2, the Apple Macintosh operating system, and Unix.

Popular operating environments include Microsoft's Windows for DOS; the Presentation Manager for OS/2; Finder and MultiFinder for Apple Macintosh; and OSF/Motif and SUN/OpenLook for Unix.

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(continued)

DOS Dos is the OS in use on IBM and compatible

microcomputers. Dos was designed as a single-user, single-tasking

operating system. Dos uses a text-based, command-line user interface. DOS uses a menu-driven user interface by running the

DOS shell command. Adding an operating environment to DOS, improves

the user interface and ease of use and increases its functionality.

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(continued)

OS/2

OS/2 is a 32-bit OS created by IBM. OS/2 is a single-user, multitasking OS that employs

virtual memory and also runs applications made for other operating systems including DOS.

Software designed specifically for OS/2 cannot be run on DOS-based computers.

OS/2 comes bundled with a GUI operating environment called Presentation Manager.

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(continued)

Macintosh Operating System

The Apple Macintosh OS is runs on the Motorola 68000 series of microprocessors.

The system has little in common with DOS or OS/2. It is a single-user and supports multitasking OS. The Apple Macintosh OS has always come with an

operating environment, called the Finder, which provides a GUI.

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(continued)

Unix

Unix was developed at AT&T's Bell Labs. Unix is a multiuser, multitasking OS that uses a

command-line user interface. Unix was written in the C programming language.

This made Unix more portable, i.e., less machine-specific, and easily moved to any size computer that could run C.

There is no standard version of Unix.

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(continued)

Unix (continued)

Popular operating environments for Unix are OSF/Motif and SUN/OpenLook.

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Application Software

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Objectives

1. Define application software and describe the two board categories into which application software is grouped.

2. Describe the five applications most in demand for microcomputers.

3. Define integrated software.

4. Identify sources of application software.

5. Identify the concerns of those getting started on a new application software package.

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What Is Application Software?

Many tasks that people perform manually can be done faster and more efficiently with a computer.

Application software are programs that direct a computer to complete tasks for the user.

Application software is written for a specific OS. Some application software is available in several versions for different operating systems; others have specific hardware requirements, such as minimum amount of main memory.

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What Is Application Software? (continued)

There are two board categories of application software:

generalized, and specialized.

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Generalized application software provides the framework for a great number of businesses, scientific, and personal applications.

Electronic spreadsheets, database management systems, word processors, computer-aided design (CAD), graphics, and communication fall into this category.

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Specialized application software performs a specific personal, business, or scientific processing task and cannot be changed to perform a different task.

Such software includes business-oriented, vertical market, engineering and scientific programs, educational programs, and entertainment programs.

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What Is Most Commonly Used Microcomputer Application Software?

The most popular and widely used applications with microcomputers are

word processor data manager electronic spreadsheet graphics communication

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(continued)

Word Processors

A word processor is software that lets you create, edit, manipulate, and print text and makes the job much simpler, easier, and faster.

WordPerfect and Microsoft Word are popular word processor.

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(continued)

Database Management Systems

A Database management systems were developed to store, organize, manipulate, retrieve, display, and print data.

Dbase, FoxBASE, and Paradox are popular database management systems for microcomputers.

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(continued)

Electronic Spreadsheets

A spreadsheet is software that displays, manipulates, and prints rows and columns of data.

Spreadsheets can perform a wide variety of tasks, from budgeting personal income to financial planning for a corporation.

Lotus 1-2-3 and Microsoft Excel are popular spreadsheet programs.

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(continued)

Graphics Programs

Graphics programs display data visually in the form of graphic images.

Harvard Graphics, PFS:Graph, and graphics in Lotus 1-2-3 are poplar graphics programs.

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(continued)

Communications Programs

Communication programs allow your computer to “talk” to other computers.

Additional hardware, a modem to transmit and receive your data over telephone lines, is needed.

Crosstalk and PC-Talk are popular communication software programs.

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What Is Integrated Application Software?

Integrated software is a category of application software that combines a number of applications, such as word processing, database management, spreadsheet, graphics, and communications, into a single application package.

It allows several programs to share the same user interface and data.

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What Is Integrated Application Software? (continued)

The applications are generally integrated in two major ways.

1. Data are easily transferred from one application to another.

2. A consistent interface is provided so that once a user learns a task, such as printing a file, in one application the same task can be performed in all applications without relearning it.

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What Is Integrated Application Software? (continued)

Cost is another reason to use integrated software.

Common integrated software packages include Microsoft’s Works for Windows; Spinnaker Software’s PFS:WindowWorks; and Lotus Development’s LotusWorks.

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How Can Application Software Be Acquired?

Application software can be prewritten software; in-house, custom-developed software; or outside, custom-developed software.

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How Can Application Software Be Acquired? (continued)

Prewritten Software

Prewritten software is available for purchase from a vendor, a distributor such as a computer store, or its author.

Advantages of using prewritten software:

1. It can be installed quickly; and is ready for immediate use.2. It is usually less expensive than custom-developed

application software.3. It is available for almost any task required.4. It has already been tested.5. Some can be modified to meet a user’s special requirements.

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Prewritten Software (continued)

The disadvantage of prewritten software is that it may not precisely fit the special needs of a user.

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Custom-Developed Software

Custom-developed software can be written when prewritten software does not fit the user’s need.

The main advantage of custom-developed software is that it can be tailored to exact specifications.

A major disadvantage is the cost. Skilled programmers are expensive, and determining precise specifications can be time-consuming and costly.

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How Do I Get Started with a New Application Program?

When getting started on a new application software package:

Determine system requirements before buying. Read documentation on installing and getting started. Make backup copies of master disks. Run installation program. Load application program. Use manuals, on-line help, and tutorials to learn program.

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How Do I Get Started with a New Application Program? (continued)

To install a program means to prepare it to work with your computer.

The installation program is responsible for getting the application up and running. It guides you through the installation process by presenting a screen menu of setup options. The options to be set may include the type of monitor, printer, or other peripheral device with which you work.

To load a program means to place it in main memory.

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Summary

Table 4.1 illustrates examples of the categories of software.

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Summary(continued)

Software Examples

Generalized Application Software

Specialized Application Software

System Software

Word Processing Payroll Processing Operating System

Spreadsheet Inventory Mgt. Programming Language

Compiler/interpreterExpert System Shell Class Scheduling

Paint and Draw Human Resource Mgt. Database Mgt. System (DBMS)

Desktop Publishing Insurance Claims Proc.

Presentation Graphics Utility Billing Utility

Computer-Aided Design General Ledger Performance Monitoring

Database Graphical User Interface (GUI)

Table 4.1 examples of the various categories of software

Documents

1 Chapter 8 Computer Software. 2 What Types of Software Make a Computer Useful?