Lesson 4Computer Software

Hardware vs. Software

• Computer systems consist of both hardware and software.

• Hardware has little value without software, and software cannot run without hardware to run it.

• What Is Software?• Software consists of the instructions issued to the

computer to perform specific tasks:• The software on a computer system refers to the

programs that make the computer run.• Software programs are lists of instructions in code that

the computer understands that tell the computer what to do.

How Software Programs Work

• A computer processes data by applying rules called algorithms.

• An algorithm creates a logical progression of steps needed to accomplish a task.

Software Development

• Software development is a multi-step process that begins with a need to perform a task more efficiently using a computer:

• First, the programmer breaks down the problem into a series of steps in an algorithm.

• The programmer may use a flowchart to show different paths the program will take.

• Next, the programmer writes the steps in a computer programming language or code, using formal terms and syntax.

• Then the computer translates the code into machine language it can understand and uses the translated commands to execute a program.

Debugging Software

• The software development process does not end when the computer executes the program.

• Errors in syntax or even spelling can cause problems and distort program results.

• Tests of the software find and fix “bugs” or errors in the code so it will run properly.

Types of Software

• There are literally thousands of software programs you can buy, but all of them can be grouped into one of two categories:

• Applications software

• Systems software

Applications Software

• Application software consists of programs that were created to perform a specific task.

• Application software is also called productivity software.

• The most common types of application software are– Word-processing programs– Spreadsheet software– Presentation software– Database software– Web browsers– Games

Systems Software:

• refers to the programs that are used to manage computer system resources. It coordinates and controls the resources and operations of the computer itself.

• The three categories of systems software are– Operating systems– Utility programs– Language translators

Operating Systems

• Operating systems provide an interface between the user and the computer.

• There are many brands and versions of operating systems.

• An operating system is designed to work with a specific processor.

Utility Programs

• Utility programs are designed to help perform housekeeping chores for the computer:

• Manage the computer’s resources• Perform file and folder management tasks• Clean up unused files from the hard disk• Defragment disk storage• Copy files from one disk to another• Back up data to disk or tape

Language Translators

• Computers cannot read program statements in programming language format, such as Visual Basic or Java program statements.

• Language translator programs convert program language code into machine code that can be understood by the computer.

• Once converted to machine code, the program can be run and executed by the computer.

Microcomputer Operating Systems

• If your computer is a Macintosh, you are probably using a Mac OS.

• If your computer is a PC or is PC compatible, you are most likely using one of these operating systems:– DOS– A combination of DOS and Windows– A standalone version of Windows

Mac OS

• Macintosh computers were introduced by Apple Computer in 1984.

• Macintosh had one of the first GUI operating systems, with icons that represented programs, documents, and disks.

• This was also the first operating system to provide an on-screen help system

•

Disk Operating System (DOS)

• IBM introduced its first PC in 1981. Its operating system was called DOS, which stands for Disk Operating System

• DOS is a command-line interface operating system. The user had to enter commands at a screen prompt.

• It was a single-tasking operating system, which meant that only one program at a time could be executed.

Windows

• Windows was Microsoft’s first GUI operating system, released in 1987.

• The first versions were called operating environments because they acted as a shell around the DOS operating system and worked in combination with DOS

Windows

• Applications installed on a Windows system appeared as icons that were activated by clicking them, similar to the Mac OS Finder interface.

• The earliest versions of Windows were labeled Windows 3.0, 3.1, and so on.

• The first true multitasking version of Windows was Windows 95, which also included support for networking computers.

• Windows 98 improved on Windows 95 and offered Internet integration and support for the USB bus.

• Windows 2000 was an update to Windows 98 and Windows NT and included tools for Web site creation.

• Windows XP which provided increased stability and device recognition.

• The latest version of Windows is Window 7 (2011)

Other Operating Systems

• Unix was developed by AT&T and is another early operating system that is still used today.

• It is a portable operating system, which means it can run on any hardware platform.

• Variants of Unix include the freeware operating system Linux and IBM’s AIX

Network Operating Systems

• A network operating system (NOS) is designed to allow multiple computers to be connected and talk to each other.

• The most popular networking operating systems include– Microsoft Windows XP and Windows 7 (Both

support standalone and networks.– Linux network operating system– MAC OS 10

User Interfaces

• You are probably familiar with the user interface of an operating system because it is what you see when you use the computer.

• The user interface determines how “user friendly” the operating system is.

• There are two commonly used types of operating system interfaces, command-line interfaces and graphical user interfaces.

Command-Line Interfaces

• With this interface, you must type exact commands into the computer from a command prompt.

• You must memorize many commands and keywords.

• Command-line interfaces are not as user friendly as graphical user interfaces

Graphical User Interfaces

• Menu-based interfaces were easier to use, providing options so that commands did not need to be memorized.

• The breakthrough in ease of use came with the introduction of graphical user interfaces (GUIs).

• Users manipulate on-screen icons to perform functions, usually with a mouse or other pointing device.

• Most of today’s personal computers are equipped with some type of user-friendly GUI.

Starting Your Computer

• When you start your computer, operating system commands are loaded into memory.

• Each operating system starts the computer in its own individual way.• When you turn on a computer, you boot the system.• POST (Power-on Self Test), a series of tests that check RAM and

verify that the keyboard and disk drives are connected to the computer, runs when you start your computer.

• Then the BIOS (Basic Input Output System) searches for the boot record. The hard disk drive C is typically the startup drive, so that is where the BIOS will look first for the boot record. BIOS is built-in software on a ROM chip. It contains all of the code that controls the monitor, keyboard, disk drives, and other components. The boot record, which includes several files, is loaded into RAM. These files contain programming configuration instructions for hardware devices and software applications that you may have installed on your computer.

Starting Your Computer cont.

• Next, the software drivers are loaded. Drivers enable you to use your printer, modem, scanner, or other devices. Generally, when you add a new device to your system, drivers are installed for that device.

• Next to be loaded is the GUI or graphical user interface, such as Windows XP. When loading the GUI, the operating system reads the commands for your desktop configuration. It also loads whatever programs you have previously specified into the Windows Startup Folder.

• If everything goes as it should, the GUI displays the desktop and the computer is ready to use.