Unit 4: Software Basics: The Ghost in the Machine

After reading this chapter, you should be able to:

• Describe three fundamental categories of software and their relationship
• Explain the relationship of algorithms to software
• Discuss the factors that make a computer application a useful tool
• Describe the role of the operating system in a modern computer system
• Outline the evolution of user interfaces from early machine language programming to futuristic virtual reality interface
• Compare character-based user interfaces with graphical user interfaces and explain the trade-offs involved in choosing a user interface

John von Neumann Invents the Invisible

John von Neumann, one of the greatest mathematicians of the 20th century, became technical advisor to

J. Presper Eckert and John Mauchly, who were searching for an alternative to the plug boards and patch cords used to program ENIAC.

In 1945 he wrote the first draft of a paper that drew on their ideas. The paper called for storing the computer's program instructions with the data in memory. Every computer created since has been based on the stored-program concept described in that paper.

 

Introduction

Software fills the communication gap between humans with problems to solve and computers that can only understand zeros and ones.

The three major categories of software are: 

• compilers and other translator programs, which allow programmers to create other software. 
• software applications, which serve as productivity tools to help computer users solve problems. 
• system software, which coordinates hardware operations and does behind-the-scenes work the computer user seldom sees.

A Fast, Stupid Machine

Although computers are commonly called "smart machines" or "intelligent machines," a typical computer is capable of doing only the most basic arithmetic operations and a few simple logical comparisons. Computers seem smart because they can perform these operations and comparisons quickly and accurately.

An algorithm is a set of step-by-step procedures for accomplishing a task. A computer program generally starts as an algorithm written in English or some other human language. A programmer's job is to turn the algorithm into a program by adding details, hammering out rough spots, testing procedures, and correcting errors.

The Language of Computers

Every computer processes instructions in a native machine language. Machine language uses numeric codes to represent the most basic computer operations&endash;adding numbers, subtracting numbers, comparing numbers, moving numbers, repeating instructions, and so on.

Today most programmers use programming languages like BASIC and C that fall somewhere between natural human languages and precise machine languages. For a computer to understand a program written in one of these languages, it must use a compiler or other translator program to convert the English-like instructions to the zeros and ones of machine language.

As translators become more sophisticated, programmers can communicate in computer languages that more closely resemble natural languages&endash;the languages people speak and write every day.

Most tasks that required programming two decades ago can now be accomplished with easy-to-use software applications&endash;tools like word processors, spreadsheets, and graphics programs.

Software applications allow users to control computers without thinking like programmers.

 

Consumer Applications

The computer applications explored in this book are:

• word processing and desktop publishing (Chapter 5)
• spreadsheets and other number-crunching applications (Chapter 6)
• computer graphics and multimedia (Chapter 7)
• databases for information storage and retrieval (Chapter 8)
• telecommunications and networking (Chapter 9)

The differences between buying computer software and music software (CDs or cassettes) are:

• A computer software package generally includes printed documentation&endash;tutorial manuals and reference manuals that explain how to use the software. Most modern software packages have some kind of on-line documentation.
• Most software companies continually work to improve their products by removing bugs and adding new features.
• A computer software buyer must be concerned with compatibility.
• According to the warranties printed on many software packages, the applications might be worthless even if you have compatible hardware and software.
• When you buy a typical computer software package, you're not actually buying the software. Instead you're buying a software license to use the program on a single machine. Virtually all commercially marketed software is copyrighted, so it can't be legally duplicated for distribution to others; some disks (mostly games) are physically copy-protected, so they can't be copied at all.

Not all software is copyrighted and sold through commercial channels. Electronic bulletin boards, the Internet, user groups, and other sources commonly offer public domain software (free for the taking) and shareware (free for the trying, with a send-payment-if-you-keep-it honor system).

In general, most successful software products share two important characteristics.

• Most successful software applications are built around visual metaphors of real-world tools.
• Most popular computer applications are successful because they extend human capabilities in some way, allowing users to do things that can't be done easily, or at all, with traditional tools.

Integrated Applications and Suites: Multipurpose Software

While most software packages specialize in a particular application&endash;word processing, graphics, or whatever&endash;integrated software packages include several applications designed to work well together and generally include at least these five application types:

• word processing
• database
• spreadsheet
• graphics
• telecommunications

The parts of an integrated package may not have all the features of their separately packaged counterparts, but integrated packages still offer several advantages:

• They cost considerably less than the total cost of purchasing individual programs that perform all of the separate functions.
• They apply a similar look and feel to all of their applications, so users don't need to memorize different commands and techniques for doing different tasks.
• They allow quick and easy transfer of data between applications. Many include interapplication communication features, so changes created in one application are automatically reflected in other applications.

Many software companies offer application suites (or office suites )&endash;bundles containing several application programs that are also sold as separate programs. The price of a suite is generally less than the total price of individual applications purchased separately, but more than the cost of an integrated package. Suites generally have more features than integrated programs, but also make greater demands on system memory, disk storage, the CPU, and the user who must learn many extra commands and options.

Vertical-Market and Custom Software

Applications designed specifically for a particular business or industry are sometimes called vertical-market applications. Vertical-market applications tend to cost far more than mass-market applications, because companies that develop the software have very few potential customers through which to recover their development costs. In fact, some custom applications are programmed specifically for single clients.

Software takes care of many messy details of computing for you. These details, and hundreds of others, are handled behind the scenes by system software, a class of software that includes the operating system and utility programs. (By some definitions, system software also includes translator programs.)

What the Operating System Does

Virtually all general-purpose computers today depend on an operating system (OS) to keep hardware running efficiently and to make the process of communication with that hardware easier.

The operating system, as the name implies, is a system of programs that perform a variety of functions, including:

• Communicating with peripherals
• Coordinating concurrent processing of jobs
• Large, multiuser computers often work on several jobs at the same time&endash;a technique known as concurrent processing. State-of-the-art parallel processing machines use multiple CPUs to process jobs simultaneously
• If a PC has multitasking capabilities, the user can issue a command that initiates a process and continue working with other applications while the computer follows through on the command
• Memory management
• Resource monitoring, accounting, and security 
• Program and data management

Utility Programs

Utility programs serve as tools for doing system maintenance and some repairs that aren't automatically handled by the operating system.

Where the Operating System Lives

Some computers&endash;mostly game machines and special-purpose computers&endash;store their operating systems permanently in ROM (read-only memory) so they are ready to go to work as soon as they are turned on. But because ROM is unchangeable, these machines can't have their operating systems modified or upgraded without hardware transplants.

Most computers include only part of the operating system in ROM&endash;the remainder of the operating system is loaded into memory in a process called booting.

As software evolves, so does the user interface&endash;the look and feel of the computing experience from a human point of view.

Some popular user interfaces are:

• MS-DOS, the operating system that's standard equipment in millions of IBM-compatible computers (computers that are functionally identical to an IBM personal computer and therefore capable of running IBM-compatible software)
• Apple's Macintosh, the most popular alternative to IBM-compatible computers
• Microsoft Windows, software that provides a Macintosh-like user interface for IBM-compatible computers

A Character-based User Interface: MS-DOS

MS-DOS (Microsoft Disk Operating System, sometimes called just DOS) was the most widely used general-purpose operating system in the world.

IBM chose PC-DOS&endash;the IBM brand of MS-DOS&endash;as the operating system for its first personal computer in 1981.

MS-DOS was designed with a character-based interface&endash;a user interface based on characters rather than graphics.

With a command-line interface, the user types commands and the computer responds to the commands.

It's most common for applications to have a menu-driven interface that allows users to choose commands from on-screen lists called menus.

Graphical User Interfaces: Macintosh and Windows

The Macintosh operating system sports a graphical user interface (sometimes abbreviated GUI, pronounced "gooey") that determines what the user wants by monitoring movements of the mouse. With the mouse the user points to pictures, known as icons, that represents files, folders (collections of files), and disks.

Documents are displayed in windows&endash;framed areas that can be opened, closed, and rearranged with the mouse.

The user selects commands from pull-down menus at the top of the screen.

When you turn on the Macintosh, you see a visual representation of a desktop with a menu bar at the top. An open window shows the contents of the hard disk.

Each icon in the window represents a file or a folder containing other files.

The operating system displays dialog boxes when two-way communication is called for.

Working with a Macintosh is a very different experience from working with an IBM-compatible computer running MS-DOS. But the difference has less to do with the platform&endash;the hardware on which the software runs&endash;than with the software itself.

Microsoft Windows was originally a type of program, known as a shell, that put a Macintosh-like face on MS-DOS. Modern versions of Windows have evolved into complete operating systems and have come to dominate the operating systems market.

Why WIMP Won

Graphical user interfaces with windows, icons, menus, and pointing devices (sometimes called WIMP) offer several clear advantages from the user's point of view:

• They're intuitive.
• They're consistent.
• They're predictable.
• They're forgiving.
• They're protective.
• They're flexible.

Graphical user interfaces and friendly operating systems generally require more expensive graphic display systems, more memory, more disk space, and faster processors to work efficiently.

The computer industry is rallying behind graphical user interfaces.

GUIs Today

Most personal computers today are built on one of two hardware platforms: the Intel-based platform used by IBM-compatible PCs and the Motorola-based Macintosh platform.

Besides the Macintosh and Windows 9x operating systems, others available today include:

• IBM's OS/2, a high-powered operating system that can run applications developed for both DOS and Windows.
• Microsoft Windows NT, a network-oriented operating system based on Windows, designed to run on high-end PCs and workstations.

   

• UNIX, the powerful operating system that runs on everything from PCs to mainframes. UNIX isn't a GUI, but many shell programs and UNIX variations offer GUI interfaces.

Tomorrow's User Interfaces

Here are some likely candidates for future user interfaces:

•  
• The end of applications. Replaced by all-purpose tools. 
• Natural-language interfaces. Natural-language processing lies in the domain of artificial intelligence, Unit 13's subject. 
• Agents. Artificial intelligence research being done today may lead to intelligent agents that "live" in our computers and act as digital secretaries, anticipating our requests, filling in details in our work, and adjusting the computerized workspace to fit our needs. Chapter 16 describes agents and other futuristic user interface technologies in more detail. 
• Virtual realities. Further into the future many experts predict that user interfaces will become so sophisticated that we'll be hard pressed to detect the difference between the real world outside the computer and the virtual reality created by the computer.

Rules of Thumb: The Concise Computer Consumer's Guide

Nine criteria to consider if and when you decide to buy a computer are:

• Cost. Buy what you can afford, but be sure to allow for extra memory, extended warranties, peripherals (printer, hard disk, modem, cables, and so on) and, above all, software. 
• Capability. Be sure the machine you buy can do the job you need it to do, now and in the future. 
• Capacity. Buy a computer that's powerful enough to meet your needs. 
• Customizability. Computers are versatile, but they don't all handle all jobs with equal ease. 
• Compatibility. Will the software you plan to use run on the computer you're considering? 
• Connectivity. In the age of connectivity, it's not unusual for competing computers to be able to translate foreign file formats into readable documents. 
• Convenience. Just about any computer can do most common jobs, but which is the most convenient? 
• Company. If you try to save money by buying an off-brand computer, you may find yourself the owner of an orphan computer. 
• Curve. Most models of personal computers seem to have a life span of just a few years&endash;if they survive the first year or two.

algorithm, application suite (office suite) , booting , bug, character-based interface

command-line interface, compatability, compiler, concurrent processing, copy-protected software

copyrighted software, desktop, dialog box, directory, documentation, emulation, graphical user interface (GUI)

integrated software, machine language, MS-DOS, multitasking, platform, prompt, public domain software

shareware, shell, system software, user interface, virtual reality

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