INTRODUCTION TO COMPUTER

What is a computer? Computer is a machine that performs tasks or calculations according to a set of instructions, or programs. Computers process data into information. Data is a collection of unprocessed items, which can include text, numbers, images, audio, and video. In simple terms, when you are watching a movie on a computer or listening to a song, or viewing a picture, then the movie file qualifies as data in the computer. Same goes with the audio songs and picture file. Computers are automatic, electronic machines that accept data & instructions from a user (INPUT) store the data & instructions (STORAGE) manipulate the data according to the instructions (PROCESSING) Output the results to the user (OUTPUT)

INFORMATION PROCESSING CYCLE

Computers process data (input) into information (output). Computers carry out processes using instructions, which are the steps that tell the computer how to perform a particular task.Computers after processing data (input) can either store (storage) it or can get it out of the computer (output). A computer often holds data,information, and instructions in storage for future use. Some people refer to the series ofinput, process, output, and storage activities as the information processing cycle. Computers process several data items to print information in the form of letters, a cash register receipt etc.

THE COMPONENTS OF A COMPUTER

A Computer is made up of tangible components called Hardware and the other intangible side is known as the Software. When using a computer we use the hardware to interact with the software. The hardware works together with the software to have a fully functional computer. Hardware components are the physical, tangible pieces that we can see and touch Software is a collection of related instructions organized for a common purpose and is sometimes referred to as Program Program a sequence of instructions to accomplish a result a computer processes information under the direction of a program Data Information to be processed by a program Example Data: for each employee, the employee number, hours worked & monthly pay rate Program: instructions on how to process the data to produce monthly pay slips.

Figure 1 : Overview of a typical Computer Function

HARDWARE
A computer contains many electric, electronic, and mechanical components known as hardware. Computer hardware is that part of the computer which we can touch and feel. These components include input devices, output devices, a system unit, storage devices, and communications devices. INPUT DEVICES An input device is any hardware component that allows you to enter data and instructions into a computer. Five widely used input devices are the keyboard, mouse, microphone, scanner, and Web cam.

A computer keyboard contains keys you press to enter data into the computer. The keyboard,
based on a standard QWERTY typewriter, has historically been the most common input device. Some keyboards contain a numeric keypad (a set of keys in the form of a calculator keypad) that is used for entering numbers conveniently and easily. Keyboards may also have Internet keys, CD/DVD controls, and multimedia keys. While most keyboards are connected to the computer by a cable, there are wireless keyboards that transmit their input by means of infrared signals or Bluetooth.

A mouse is a small handheld device. With the mouse, you control movement of a small symbol on
the screen, called the pointer, and you make selections from the screen. A mechanical mouse contains a ball that rolls along a flat surface, moving a cursor (pointer) on the computer screen. An optical mouse uses light signals to detect the movement of the mouse and thereby move the pointer on the screen. Through the use of one to four buttons on top of the mouse (and a wheel on some versions of the mouse), the user can select and manipulate objects represented on the screen as icons (symbols). The mouse is a convenient and effective way to interact with the graphical user interfaces (GUIs) that dominate the current computer environment.

Touchpad: This input device is a small rectangular surface that operates by means of pressure and
motion, and allows the user to perform all of the functions of a mouse by touch. Moving the fingertip across the touch pad moves the cursor across the screen. Tapping the touch pad acts as clicks and double-clicks. Touchpads are most commonly found on laptop computers.

Touch Screen: This input device is often used in public places, such as shopping centers, hotels,
and airports, where users may not have much experience working with computers. The user simply

touches the screen for the desired menu item. This feature is can be checked out at the National Bank Ntcheu Branch.

Audio Input Devices: These devices allow music, speech, and other sound effects to be used as
input. Sound may be entered through a microphone, electronic piano keyboard, tape player, and CD player. For high quality sound recording, a sound card needs to be installed in the computer. For some electronic input devices a special serial port, called a musical instrument digital interface (MIDI), is required.

Video Input Devices and Digital Cameras: Video input devices and digital cameras allow
optical and graphical images to be entered into the computer for storage and processing. Digital cameras allow the user to store still-pictures as digital files that can be used by the computer like other graphic images. Video input devices enable the user to store and process full-motion images generated from camcorders and VCRs. One well known device is the WEBCAM. A Web cam is a digital video camera that allows you to create movies or take pictures and store them on the computer instead of on a tape or film.

Optical Scanning Devices: Optical scanning is the process of digitizing textual or graphic
images. The scanner is a light-sensing device that converts an image into an analog signal that in turn is converted into a digital signal for computer storage and processing. The resulting file is called a bitmap (.bmp files). Optical scanning is a popular technique for capturing photographs for computer usage but it may also be effectively used with printed and handwritten text. In short ascanner converts printedmaterial (such as text and pictures) into a form thecomputer can use.

Optical Character Recognition (OCR) Devices: OCR devices convert typed and, in some
cases, handwritten data into electronic input. This allows paper source documents to be converted to electronic form without rekeying. Although OCR devices can recognize handwritten characters and a variety of fonts and typefaces, this technology is not perfectly reliable. In spite of high error rates, OCR is a cost-effective means of converting large volumes of source documents that otherwise would need to be keyed manually. One notable aspect of input devices is the degree to which a device eliminates the need for manual data entry. Manual data entry is a common source of error. Some input devices require fully manual data entry; e.g., keyboards. Others have done away with manual entry completely; e.g., optical scanners. PROCESSING SYSTEM Once data has been input into the computer and stored, the computer must be able to retrieve and manipulate it in useful ways. This task is handled by the hardware that makes up the central processing system, which includes the primary memory, the central processing unit (CPU), expansion cards, ports, buses, and connectors. The various parts of the computer system are connected through a printed circuit board called the system board or motherboard. The system board contains the primary memory, the CPU, the system clock, expansion slots, and expansion ports. In a PC, the central processing system is housed a box-like case called the system case or system unit. SYSTEM UNIT The system unit is a case that contains the electronic components of the computer that are used to process data.

EXPANSION SLOTS Peripheral devices, such as keyboards, disk drives, and monitors, are connected to the computer through expansion circuit boards (also called expansion cards, adapter cards, add-ins, add-ons, and interface cards) plugged into the expansion slots provided on the motherboard. Types of expansion cards include:

A disk controller card connecting a disk drive An accelerator card increasing CPU speed A video graphic card connecting a monitor A fax/modem card connecting a telephone line A memory card for adding memory A PC-TV card for connecting to a television A sound card connecting external speakers A game card connecting a joystick An interface card connecting peripherals such as mouse devices and scanners A local area network card connecting other computers

Laptops and notebooks have a special type of expansion card called a PC card. Unlike desktop-type expansion cards, you can add or change a PC card without opening the system case of the computer. The PC card is simply plugged into the appropriate opening in the laptop or notebook. PC cards can be used to add memory, fax/modem, disk drives, and sound capabilities. The Universal Serial Bus (USB) uses a new approach to connecting peripheral devices to the computer. It does away with the need to install new expansion cards for each new device. Instead, USB-capable devices are connected to each other in a daisy chain, and only one device is actually connected to the computer through a cable attached to the USB port. The USB port feeds into the USB, which in turn connects to the PCI, and then on to the motherboard.

STORAGE DEVICES

Inputs are sent to either memory or storage, waiting subsequent processing by the computer. With regards to computers, there is a commonly accepted distinction between the terms memory (or primary memory) and storage (or secondary storage). Memory refers to the instructions, information, and data waiting for immediate processing. Memory is saved electronically on memory chips. Storage, information and instructions are saved on magnetic or optical media. It is faster to access data and instructions from primary memory than from secondary storage media, but the information in memory is usually volatile; i.e., it disappears when the computers power is turned off.
The information saved in storage media is nonvolatile and remains in the computer even when power is off.Storage holds data, instructions, and information for future use. For example,

computers can store hundreds or millions of customer names and addresses. Storage holds these items permanently. Storage and memory are usually measured in bytes, which consist of 8 bits (binary digits of 0 or 1). A single byte is used to encode a single character (letter or number). One thousand bytes are a kilobyte (KB). One million bytes are a megabyte (MB). One billion bytes are a gigabyte (GB). One trillion bytes are a terabyte (TB). For comparison, the average book

contains about 1 MB of information and the storage capacity of human memory is about 10 TB (or 1 million books). HARD DISKS: are magnetic-based storage media. Both the hard drive and the hard disks are usually installed inside the computer. Portable external hard drives are connected to the computer by a cable. Current PC hard disks typically have a capacity from 20 to 500 GB. Hard drives have a faster data access time than memory cards & flash disks. Data access time is the time required to locate a piece of stored information in storage and retrieve it into primary memory or the CPU. The hard disk is considered the main storage of a typical computer system. REMOVABLE HARD DISKSare magnetic-based hard disks that can be removed from the hard disk drive and easily transported. The disk drive that reads from and writes onto the removable hard disk is either installed in the computer or attached to the computer by a port. The portable hard disk is encased in a plastic or medal container for protection.

COMPACT DISKS: are optical storage media that employ laser technology. CDs are 4.75 inches in
diameter and can hold up to 650/700 MB. CDs are often read-only, although many PCs are now equipped with CD drives that allow the user to record information on the CD. Some writable CDs can be recorded on only once. These are designated as CD-R (compact disc-recordable). Others CDs can be recorded on multiple times and are designate as CD-RW (compact disc-rewritable). Video data (e.g., movies) can be stored on a specialize type of CD called CDDVDs (digital video discs). As with CDs, there is recordable variation of DVDs (DVD-R) that allows the user to record video data from his or her computer, provided that the computer is equipped with a DVD writer. DVDs can hold up to 4.7GB of memory and some double layer DVDs can hold up to 7.4GB of data. Blu-ray Discs can store about 46 hours of standard video, or storage of up to 50GB. Unlike typical CDs or DVDs which can work on most CD/DVD readers, Blu-ray discs require a special Blu- ray ROM drive. Thanks to the improvement of technology everyday, most of todays laptops or desktops come with a ROM drive that can read CDs, DVDs and Blu-ray discs as well.

A USB flash drive is a portable storage device that is small and lightweight enough to be
transported on a keychain or in a pocket. The average USB flash drive can hold about 512MB-128GB of memory. You plug a USB flash drive in a special, easily accessible opening on the computer known as a USB Port. OUTPUT SYSTEM Like the input system, the output system provides an interface through which computers and humans can interact with one another. However, now the human is on the receiving end of the process. Output devices are used to display input data that has been processed by the computer into useful output information. Through its output system, the computer presents the data it contains in a form that the user can understand. The presentation is typically in one of four forms: graphics (e.g., charts and photographs), text (e.g., words and numbers), video (e.g., photographic images in motion), or audio (e.g., music and speech). Probably the most common output devices are monitors for producing temporary displays (soft copies) and printers for producing paper copies of documents (hard copies).

MONITORS A monitor, or screen, can display graphics, text, and video output. To display video in the monitor, the computer needs a video card (or graphics card) for converting the digital signal (i.e., data in the form of 0s and 1s) from the processor to an analog signal (i.e., data in the form of a continuous electrical wave) that the monitor can interpret. Monitors come in three main varieties: cathode-ray tubes (CRT), flat-screen liquid-crystal displays (LCD), and gas-plasma displays. All of these are now capable of either monochrome (black-andwhite) or color displays. Desktop PCs usually come with CRTs, although flat-screen LCDs are becoming more common. Flat-screen LCDs are generally used in notebooks and laptops. The common desktop CRT sizes range from 15 to 21 inches. Laptop LCDs sizes are commonly 14.1 to 15.1 inches. Gas-plasma displays are capable of larger displays with good resolution and can be in excess of 42 inches. PRINTERS It was once thought that as computers became more common in business and in the home, we would move toward a paperless society. That is, all data would be circulated and used in electronic form, eliminating the need for printed material. This vision has yet to be realized. In businesses, homes, and most settings where computers are found, users still produce hard copy (information in printed form). For most applications, soft copy (information in electronic form) is not adequate. To produce hard copy, a computer must be connected to a printer. This is typically done through a parallel port, which enables the computer to communicate with the printer one byte at a time. Microcomputers may have one or more parallel ports. OTHER OUTPUT DEVICES Speakers and headsets are the two most common devices used for audio output. A voice output device produces voice commands by imitating phonic sounds. These prerecorded phonic sounds produce synthetic-sounding words. Some telephone companies use voice output to automate directory assistance, and some automobiles contain voice output devices that remind drivers to fasten their seat belts. Projectors are used to display graphics, text, video output from a computer. In the case of projectors, the output is displayed onto a screen for an audience to view instead of into a monitor for a single user's viewing. Like monitors, projectors are attached to the computer through a parallel port. Projector technology varies widely, but the two most common types are LCDs projectors and digital light processing (DLP) projectors. COMMUNICATION SYSTEM It is sometimes helpful to link two or more computers together so that they can communicate with one another directly without a human intermediary. To accomplish this task, a computer draws on its communication system. Communications is, thus, the third main function of which computers are capable, the other two being data storage and data processing. In order for two or more computers to communicate, specialized hardware is required. First, the multiple computers must be connected together through transmission media over which the data are transmitted. Second, there must be communication processors that put the data in a form that can be transmitted through the transmission media and convert the received signals into a form the computers can use.

SOFTWARE
A computer system needs more than the hardware described above in order to function. The hardware by itself, even when powered-up, is incapable of producing useful output. It must be instructed how to direct its operations in order to transform input into output of value to the user. This is the role of software; i.e., to provide the detailed instructions that control the operation of a computer system. Just as hardware comprises the tangible side of the computer, so software is the intangible side of the computer. If the CPU is the physical brain of the computer, then software is its mind. Software instructions are programmed in a computer language, translated into machine language, and executed by the computer. Between the user and the hardware (specifically, the memory), generally stand two layers of software: system software and application software. SYSTEM SOFTWARE System software directly controls the computers hardware, whereas application software is one level removed from hardware. System software manages the computers resources, enables the various components of the computer to communicate, runs application software, and makes the hardware respond to the users needs. When the system software operates efficiently, the difficult operations of controlling the hardware are transparent to the user. System software includes 2 essential types: The operating system provides an interface between the computer hardware and the user or the application software. Because of its central importance, the operating system will be discussed in more detail below. Utility programs perform various specialized "housekeeping" tasks, such as file management, virus protection, disk defragmentation, program installation and uninstallation, file and disk back up, disk formatting, and providing screen saver programs. This list is far from exhaustive. The user directly controls most utility programs, although some utility programs can be set to run automatically (e.g.; screen savers and disk error scanning).

OPERATING SYSTEMS The operating system has two primary functions. First, it manages the computer's resources the computer's hardware and any external devices. For example, the operating system controls the CPU, accesses RAM, executes programs, receives input from the keyboard or other input device, retrieves and saves data to and from secondary storage devices, displays data on the monitor, and controls the printer. Second, the operating system contains instructions for running applicationsoftware. To make computer systems easy to use, the interface (link) between the user and the hardware has become simpler and more intuitive. Particularly important for the development of user -friendly computers is the graphical user interface (GUI). The GUI allows the user to interact with the computer through icons (graphic symbols) on the screen. These icons can represent a variety of things, including computer disks, folders, documents, and software programs. The user instructs the computer to perform particular tasks by pointing to and manipulating the appropriate icons with a mouse. Operating systems not GUI-capable, e.g., UNIX, require the user to input commands by typing in words or pressing specially defined keys. This set-up is called a command-line interface. Another important function of the operating system is that of configuring the external devices. Each device must communicate to the computer, a process requiring a device to have its own program,

referred to as the device driver. The operating system coordinates the installation of this software and ensures its proper functioning. These procedures are often done manually but in some cases the process is automatically perform by the operating system (called Plug and Play). Operating systems that allow only one user to run one program at a time are called single user or single tasking operating systems. Most current operating systems and computers have moved beyond this stage to multitasking. In multitasking, the operating system allows more than one task or program to be executed at a time in a single-user computer. Operating systems that address more memory can run several tasks simultaneously. A computers multitasking capability is also limited by the amount of RAM it contains. There are numerous operating systems. Several of the most popular are discussed below: Macintosh Operating Systems (Mac OS) was introduced in the 1984 and was the first commercial GUI platform. The latest version supports multitasking, includes multiple Web browsers, and has built-in networking capability. Macintosh is owned by Apple Inc and most people just call it Mac OS in short. Mac Os is characterized by very powerful graphics and very appealing designs. Unlike other Operating Systems that we will explore later, Mac OS runs only on its hardware and this makes it expensive. Mac Os is mostly used in USA, Canada & Europe and due to its hardware limitations, a lot of people in other regions of the world prefer not to buy it due to technical support issues. Microsoft Windows Operating Systems are a GUI-capable, multitasking operating systems. Microsoft Operating systems take advantage of todays more powerful microprocessor chips, such as the Intel Pentium, which address more memory and run faster than the older microprocessors. Microsoft Windows Operating Systems are user-friendlier than other Operating Systems and due to this, Microsoft Windows OS owns about 90% of the worlds market share of Operating Systems and no operating systems are up to take this share anytime soon. Microsoft is the largest software producing company and a lot of computer games and application are developed for this OS. Examples of Microsoft Operating Systems are Windows 95, Windows 98, Windows 2000, Windows XP, Windows 7 & the latest Windows 8.1 (We will tackle Microsoft Windows XP in our next hands-on lessons.) Microsoft Windows OS unlike Mac OS can run on several hardware systems like Dell, Acer, HP and other hardware brands. The most significant similarity between Microsoft and Mac OS is that, they both are commercial Operating Systems i.e. you have to buy licenses to own these OS Linux is an interesting operating system because it is not proprietary software. Its code has been made publicly available (called open-source software). This allows users to customize the software to meet their personal needs and to share improvements made with others. Linux is free, which means you dont have to buy a license to own this OS though we also have some commercial Linux like Red-Hat Software. Linux is characterized for being virus free, a bit hard-to-use, a very good alternative for Windows Operating OS and sometimes Mac OS. Sometimes you will hear people say that Mac OS is Beautified Linux because the kernel (brain) of Mac OS is made up of Linux. Examples of Linux distributions are Ubuntu; Fedora, Puppy Linux, Uberstudent and many other distributions. Linux is more similar to Windows OS than Mac OS in the way that they both run on other hardware brands unlike Mac OS which runs only on its hardware. The main difference between Linux and other OS is that Linux is non-commercial and you can easily customize it according to your needs.

APPLICATION SOFTWARE Application software enables the user to direct the computers processi ng system in the tasks of manipulating and transforming input data into useful output information. Furthermore, it allows the

user to alter the information generated by the processing system; e.g., how the information is presented. This is the type of software with which most users interact. It is the usual interface between user and computer. Rarely do users directly manipulate systems software, especially the operating systems software. Application software can be written for a specific users applicati on (custom software), or it can be mass-produced for general use (commercial or packaged software). Naturally, custom software is usually far more expensive than commercial software. An accounting package written for a specific company might cost many thousands of kwachas, whereas a commercial accounting package might cost only a few thousand kwachas at a retail store. The advantage of custom software is that it is tailored to the users specific needs and can be seamlessly integrated into the users existing software. Not only is commercial software less costly, it is also available immediately, and the package can be evaluated before being purchased. Application software comes in an incredible variety. It is available for business, personal, educational, communication, and graphic design purposesto name the more usual categories. There is almost certainly a software package somewhere available to suit any need. If not, there are programmers ready to be hired to build it. For our purposes, we will limit our discussion to the four types of application software most likely to be useful to accounting and business students: word processing, spreadsheet, database, and presentation graphics. These four applications are frequently sold together in a single software package. Three of the most popular packages are Adobe Master Collection, Microsoft Office 2007, and Cyberlink Media Suite. In addition to the four "standard" applications, these packages usually include email, Internet, video processing, and desktop publishing applications. Word processing programs allow the user to quickly and easily create and revise texts on the computer screen. By using word processing applications, the user can format documents with ease, changing font size, margins, color, etc. Different types of documentse.g., letters, memos, and reportsare often preformatted in the application. Microsoft Word 2007 (which we will learn later) is a word processing software so capable and more than capable that, in most businesses, it has become the usual tool for creating documents. Most of the posters you see pinned to trees and poles are designed using Microsoft Word. Spreadsheet programs are especially useful in business and accounting. The electronic spreadsheet consists of rows and columns of data, which the user can easily edit, copy, move, or print. Using numeric data entered in the spreadsheet, the computer can perform numerous mathematical calculations automatically, many of impressive sophistication (e.g., statistical, logical, and engineering functions). One of the spreadsheet programs most powerful features for business purposes is that it enables the user to do what-if analyses on existing data and to input different data for various scenarios. Non-numeric data (e.g., names and dates) may also be entered in a spreadsheet. Spreadsheets can perform some non-mathematical operations (e.g., sorting and filtering) on this data, although this type of analysis is not a spreadsheet's strength. Microsoft Excel 2007 is a powerful spreadsheet software that we will learn later that does all of the things mentioned earlier. Database software allows the user to enter, store, maintain, retrieve, and manipulate data. In some ways, databases pickup where spreadsheets leave off, although a fairer assessment is probably that the relationship between the two types of software is reciprocal. Database software is certainly more efficient and effective at handling non-numeric data than is spreadsheet software. Conversely, numeric data is usually easier to manipulate in a spreadsheet. In most databases, data is entered to

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