Introduction to Computers


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Introduction to Computers

  1. 1. The American University in Cairo Academic Computing Services Introduction to Computers By Soumaia Al Ayyat Spring 2001 Table Of Contents: What is a Computer? Data Representation Connection Ports for devices The standard multiples of the byte or bit are Standard measurements for each device Computer Classifications Computer Generations The Famous Computer Brands Software Keyboard Keys What is a Computer? A computer is an electronic device that allows us to process information, perform mathematical operations and store data. The main components of a computer are: 1. Input Devices: these devices allow entrance of raw data inside the computer system. These include the keyboard, the mouse, joystick, the microphone, a touch screen, a pen tool and much more. 2. Central Processing unit (CPU): this unit is responsible for processing the input data using some programmed algorithms and written programs and returns back some results. The processing unit consists of the processor that resembles the brain of the computer. Part of this processor is called the Arithmetic Logic Unit (ALU). The ALU performs all the needed arithmetic operations and some logic operations.
  2. 2. The American University in Cairo Introduction to Computers Academic Computing Services Main Storage Area Data needed for processing Central Input Processing Output Raw Data Output Result Device Device Unit Information to be stored Secondary Storage Area Life Cycle of Data Processing inside the Computer 3. Output Devices: the computer displays the results of performed operations through these devices. These include the screen, the printer, the speakers and more. 4. Main Storage: this component is needed to store some data and processed information. This portion is essential for the CPU to use as a scratch paper while performing some processing. The Main memory consists of: the Read-Only Memory (ROM) and the Random Access Memory (RAM). ROM stores the necessary information needed by the CPU. The manufacturer creates this portion of memory and the computer cannot write on it. That is why it is called a read-only memory. RAM allows read and write access of the computer. The CPU utilizes the RAM as a scratch pad. In addition, there is another fast-access memory totally used by the CPU; it is called Cache. The Cache memory is very fast when compared to the RAM but it is very expensive. Accordingly, the cache size is smaller compared to the RAM size. Peripherals: In addition, there is a set of useful peripherals that add new functionalities to computers. Among these peripherals we may find the following: - Secondary storage: This is external means of storing data. This includes the hard disks, the floppy disks, the compact disks (CD), Digital Video Disk (DVD), jazz tapes and zip tapes. These devices have bigger storage areas and more persistent than the Main memory storage, yet the speed of accessing information from them is low compared to Main Memory. - Multimedia devices: these are external devices can be added to the computer to allow input of sound tracks either through a microphone, musical instruments, line in and the like. To produce digital sound from the computer, you need a professional sound card added to the computer. The output sound and music can be heard through speakers, headphones, line out and the like. - Printers: these are output devices that allow you to have a printout (hard copy) of the edited text and graphics. The job of a printer is to put on paper what you see on your monitor. Some printers are based on Laser technology; these are called Laser printers. Others use ink in the printing process; they are called InkJet printers. 1
  3. 3. The American University in Cairo Introduction to Computers Academic Computing Services - Plotters: these professional output devices are mainly used by engineers to plot detailed diagrams processed by the computer - Modems: the Modulator demodulator (Modem) is a device responsible for modulating the analog signal of the telephone line into digital computer signals and demodulates the digital computer signals into analog signals along the telephone line. This device is quite useful to connect the computers to the Internet through the well-established network of the telephony. - Ethernet Cards: these cards are useful to connect a computer to a higher speed network onto the Internet. - Scanners: it is an input device that allows us to convert printed matter into images and text on our machines. - Compact Disks (CD): these media disks enable us to store data on them. Moreover, one can store audio data on these CDs to create audio CDs. The drive that reads and creates these CDs is called the CD drive. There are several types of CD drives as follows: - Compact Disk Read-Only Memory (CD-ROM) Drive: this drive can only read ready-made CDs. It cannot write data on them nor delete existing information on the CDs - Compact Disk Recordable (CD-R) Drive: this drive has the capability of reading information from ready-made CDs and also can generate new CDs. It can write on the CD only once. It cannot delete written information from a CD. - Compact Disk Read and Write (CD-RW) drive: this drive can read CDs, create new CDs, delete information from a CD and rewrites new information on top of the old data. This drive requires a special type of CDs (media) called CD-RW media. Data Representation Data are stored in computers in the form of electric pulses; where a 5-volt charge represents existence of information and zero-volt charge indicates absence of data. Logically, the data is represented as 0 and 1. The zero indicates zero volts, and 1 indicates 5 volts. This system is called the binary system since it depends on two digits only. You can think of this as a sort of light switch. The unit data that is represented by such a digit (0 or 1) is called a bit – stands for binary digit. Thus, each switch is the bit. In order for computers to represent meaningful data they represent each character by a combination of 8 bits called a byte. Both the bit and the byte are used as units of measurement of the device capacity in storing or processing data. The bit is represented by a lowercase b. An uppercase B represents the byte. Connection Ports for devices In order to connect these peripherals to the computer there must be connection ports at the back of the computers. These are: Parallel port:1 is an interface between the computer and a printer (or any other device that needs a parallel port connection) where the computer sends multiple bits of information to the printer simultaneously. A PC is usually configured with a 25-pin parallel port named LPT1. Serial Port: A PC is usually configured with a 9-pin serial port named COM1. Serial ports are used for the mouse and modem. SCSI: (Small Computer System Interface). SCSI is a hardware interface that allows for the connection of up to seven or 15 peripheral devices to a single expansion board that plugs into the 1 Computer Desktop Encylopedia. Multimedia Engine 1.45 The Computer Language Company Inc. 2
  4. 4. The American University in Cairo Introduction to Computers Academic Computing Services computer called a SCSI host adapter or SCSI controller. Single boards are also available with two controllers and support up to 30 peripherals. SCSI is widely used from personal computers to mainframes. USB (Universal Serial Bus): A personal computer bus that has a total bandwidth of 1.5 MB per second. Up to 127 devices can be attached. For example, a USB keyboard or monitor could host several ports for additional devices. USB is used for devices such as the mouse, keyboard, printer and scanner. USB ports began to appear on PCs in 1997. The standard multiples of the byte or bit are: - Kilobits (kb) that is 1024 bits, which is almost 1000 bits - Kilo bytes (KB) that is 1024 bytes, which is almost 1000 bytes - Mega bytes (MB) that is 1024 KB which is almost million bytes - Gega bytes (GB) that is 1024 MB which is almost thousand million bytes - Tera bytes (TB) that is 1024 GB which is almost trillion bytes - Mega Hertz (MHz) is the speed of processing data which indicates processing MB per second - Kilobits per second (kbps) are the speed of transferring data through the network, where 1024 bits are transferred per second. Standard measurements for each device Device Unit of Measurement Standard Sizes MB 64 MB – 1GB RAM Cache KB 256 KB – 1 MB MB 650 MB or 74 minutes 700 MB or 80 minutes 730 MB or 80 minutes CD-ROM (media) X (indicates speed) 50X CD-ROM drive CD-RW drive X (indicates speed) 32X read, 10X write, 4X Rewrite GB 20 GB – 40 GB Hard Disk MB 1.44 MB Floppy Disk (media) VGA Card (for display capabilities) MB 2 MB – 32 MB GB 1GB – 2 GB Jaz tape (media) 3
  5. 5. The American University in Cairo Introduction to Computers Academic Computing Services KB 100 MB – 250 MB Zip tape Kbps (speed) 56 kbps Modem KBps (speed) 10/100 KBps Ethernet Card MHz or GHz (speed) 500 MHz – 1.5 GHz Processor Page per min.(ppm) 6 ppm – 16 ppm Laser Printer Dot per inch (dpi) 2400 dpi - 9600 dpi Scanner Computer Classifications: The speed of the processor is critical in setting the number of commands that can be processed per second. This speed is measured in Hertz. Along the evolution of computers, generations of computers where determined mainly according to the enhancements applied to the processor. There are 3 types of computers based on the range of use: 2 - Mainframes: a large digital computer serving hundreds of users and occupying a special air-conditioned room. Nowadays there is a diminishing need for these mainframes. - Minicomputers: A computer built between about 1963 and 1987, smaller and less powerful than a mainframe, typically about the size and shape of a wardrobe, mounted in a single tall rack. Yet, when they were invented the speed of processors was better. They now appear in the form of high-speed servers. - Microcomputers were invented for personal use. Their performance and size went through generations of enhancements till they reached the PCs we find nowadays. Computer Generations Here is a general overview on the generations of computers up till nowadays: The generations of PCs are: Generation Range of Processor Speed XT AT 2 The three definitions are driven from 4
  6. 6. The American University in Cairo Introduction to Computers Academic Computing Services 286 16 MHz – 25 MHz 386 16 MHz – 33 MHz 486 33 MHz – 100 MHz Pentium 60 MHz – 233 MHz Pentium II 233 MHz – 450 MHz Pentium III 450 MHz – 933 MHz Pentium IV 1.0 GHz – 1.5 GHz The generations of Macintosh are:3 Generation Range of Models Range of Processor Speed Classic 128K – Color Classic II 8 MHz – 33 MHz Macintosh II Macintosh II - Macintosh IIfx 16 MHz – 40 MHz Macintosh LC Macintosh LC – Macintosh LC 630 16 MHz – 66 MHz Macintosh Performa Macintosh Performa 200 - 16 MHz – 200 MHz Macintosh Performa 6420 Quadra Quadra 605 – Quadra 950 25 MHz -33 MHz PowerPC 6100 - 9500 132 MHz – 200 MHz iBook iBook – iBook (FireWire) 300 MHz – 466 MHz iMac Bondi Blue – Early 2001 233 MHz – 600 MHz Power Macintosh G3 All-In-One - Macintosh Server 233 MHz – 266 MHz Power Mac G4 AGP Graphics – PCI Graphics 350 MHz -400 MHz PowerBook G3 PowerBook G3 - PowerBook G3 250 MHz – 400 MHz Series (Bronze Keyboard) PowerBook G4 PowerBook G4 400 MHz – 500 MHz The Famous Computer Brands are: IBM Dell Compaq Micron Gateway HP Apple Software:4 3 Information driven from 4 This material is compiled from Introductory Computer Literacy for Adults By Valerie Collins, Adult Learning Center at 5
  7. 7. The American University in Cairo Introduction to Computers Academic Computing Services Computer productivity is determined by programs which are step by step instructions telling the computer how to process data. Software can be divided into two groups, system and application. System Software: The operation of your computer is controlled by system software. As you boot the computer, the system software is stored in the computer's memory which instructs the computer to load, store, and execute an application. Examples of system software are Windows 95 and Windows 98 which use a graphical user interface (GUI) that provides visual clues (icons) to help the user. DOS, another disk operating system, is text based and not user friendly. Operating Systems: The generations of the standard operating systems for personal computers DOS DOS (Disk Operating System) is the popular text-mode operating system on early PCs Windows The most widely used operating system. Developed by Microsoft, Windows provides a graphical user interface (GUI) and master control program for running applications in desktop PCs and servers. Windows is also an environment. The Windows operating system comes in three flavors: Windows 3.x, Windows 95 and Windows NT. Windows 98 is an upgrade to Windows 95. Windows 1.0 and 2.0 The early versions of Windows were not appealing, and the hardware was too underpowered. Windows 3.x Introduced in 1990, Windows 3.0 became widely used very quickly even though it still required DOS to be loaded first. Windows 3.1 was a more stable version introduced in 1992, and Windows for Workgroups 3.11 later added built-in networking. Windows 2000 This operating system is the successor to Windows NT 4.0. Its user interface is very similar to Windows 98 or Windows NT. It is available in four flavors: - Professional: the client version, meant for desktop workstations, successor to Windows NT Workstation. - Server: "entry-level" server, designed for small deployments, and departmental file, print, or intranet servers. - Advanced Server: high throughput, larger scale servers and applications, and small to medium scale web sites. - Data Center Server: software for large-scale server clusters. UNIX A multi-user, multitasking operating system originally developed by AT&T. It is widely used on CAD and scientific workstations and network servers. Its turning point in Unix's history came when it was re-implemented almost entirely in C (a programming language) during 1972 - 1974, making it the first source-portable operating system LINUX A UNIX clone that runs on x86, Alpha and PowerPC machines. Linux is freeware. Most of the supporting apps and utilities came from the GNU project of the Free Software Foundation OS/2 A single user, multitasking operating system for PCs from IBM that runs OS/2, DOS and Windows applications. Although OS/2 is highly regarded as a robust operating system, it did not gain widespread market share. Presentation Manager (PM) was the first name for its GUI, which was later renamed Workplace Shell. The Presentation Manager name was retained to refer to the programming interface used to write OS/2 applications. Mac OS The operating system for Macintosh machines Compilers: A program that translates another program written in a high-level language into machine language so that it can be executed. 6
  8. 8. The American University in Cairo Introduction to Computers Academic Computing Services Application Software Standard, general-purpose software packages: Professional programmers write a variety of application software to satisfy needs of the public who wants to perform specific tasks on their computers. The basic types of application software are word processing, database, spreadsheet, desktop publishing, and communication. Word Processing - Word processing is the most commonly used software in schools, home, and business. A key advantage of word processing software is that users can make changes such as spelling, margins, additions, deletions, and movement of text. Once you have learned how a word processor functions, you will be able to learn other software quicker. Database Software - Database software allows us to store and manipulate large quantities of data using the computer. For example, a database can sort the names, addresses, grades and activities for all of the students in a school. It would be possible to add or delete data and produce printed reports using the database. Spreadsheet Software - Spreadsheets store numeric data that can be used in calculations. A spreadsheet is used to store grades and calculates student averages. The primary advantage of a computerized spreadsheet is its ability to redo the calculations should the data it stores be changed. Calculations can be made automatically as formulas have been preset into the spreadsheet. Desktop Publishing - Desktop publishing applications allow the user to create newspapers, newsletters, brochures, and similar types of publications. It is similar to word processing except it allows the user to use text, graphics, pictures, lines, shapes, patterns, and borders. Desktop publishing requires more skill and computer knowledge of design and layout. Presently a user can purchase an integrated program. This means that a single program performs all applications and allows data to be transferred from one application to another. Microsoft Office, Works, and ClarisWorks are examples of integrated software. Each application includes a word processing, database and spreadsheet section of the software. Image Processing - This software manipulate images, and photos. Artists and professional users can create professional graphics using such software. This software allows image improvement, such as refining a picture in a paint program that has been scanned, applying techniques that can identify shades, colors and relationships that cannot be perceived by the human eye. There are numerous other applications available. There are software programs that can be used by musicians to produce musical scores and play them on a synthesizer, programs that assist an architect in designing a building, programs that produce the special effects that you see in movies, and programs that allow electronic mail (e-mail). Every line of work you can think of has had applications developed, which can ease or enhance its effectiveness and consistency. Tailored software and in-house developed software Some customers have software with special requirements; the software developers develop these customized programs to meet the users’ needs. Keyboard Keys5 The most often used input device is the keyboard. 5 7
  9. 9. The American University in Cairo Introduction to Computers Academic Computing Services Alphabet keys The letters of the alphabet and some punctuation marks are in these three rows. Alt The Alt key doesn't do anything by itself. But if you hold it down while pressing another key, the effect of that key may be different from usual. Exactly what will happen will depend on what program is running at the time. Arrow keys These four keys are used to move the cursor on the screen. The up and down arrows move the cursor up or down one line. The left and right arrows move the cursor one character to the left or to the right. Backspace The Backspace key erases the character on the left of the cursor and moves the cursor that direction, too. Caps Lock When the Caps Lock key is on, pressing any alphabetic key will result in an upper case (capital) letter. The number and symbol keys are not affected. Control The Control key does nothing all by itself. It must be pressed in combination with other keys. When used in combination, the Control key changes the normal effect of a key. Exactly what will happen depends on the software in use at the time. The Delete key is used to erase the character just to the right of the cursor. Any text beyond the erased character is moved to the left. Delete The End key is a navigation key. It will send the cursor to the end of the current line. End The Enter key is used in several ways. In word processing, it acts like the Return key on a typewriter by starting a new line. It is also used in place of a mouse click with buttons and drop-down menus. Enter The Shift key is used in combination with the alphabetic keys to get upper case. With a numeric/symbol key using the Shift key will give Shift the character at the top of the key. The Shift key can be used in combination with the Alt and Control keys to change the effects of another key. The Escape key is used to cancel actions in progress before they finish. It is also used to close certain dialog boxes. Escape Function keys The Function keys are numbered F1, F2, F3,....F12. These are programmable keys. That is, programs can assign actions to these keys. So the same key might produce different results in different programs. Some of the function keys are becoming more standardized as to what they do. For example, F1 is most often used to access the Help file for a program 8
  10. 10. The American University in Cairo Introduction to Computers Academic Computing Services The Home key is a navigation key for the cursor. It will move the cursor to the beginning of the current line. Home The Insert key is a toggle key. That is, repeatedly pressing it will alternate between two effects: 1. Typing overtypes characters already there Insert 2. Typing inserts characters in between the characters that are already there. Some programs have an indicator on screen to show you which effect is current. But not all are as friendly. When Num Lock is on, the Numeric Keypad responds with numbers, as an adding machine. When Num lock is off, the Numeric Keypad responds as navigation keys Num Lock using the alternate markings on the keys. When the Num Lock key is on, these keys are used to enter numbers as with an adding machine. When the Num Lock key is off, the keys act as navigation keys using the alternate markings on each key. Numeric Pad When Num Lock is on, the Minus key performs subtraction on the numbers entered. Minus When Num Lock is off, the Minus key will type a hyphen like this -. Number/Symbol Keys On this row of keys you will see two characters, one at the top of the key and one at the bottom. The upper character is a symbol and is accessed by holding the Shift key down while pressing the key. Numbers can also be typed from the Numeric Keypad. When Num Lock is on, this key performs addition. When Num Lock is off, this key prints a +. Plus When Num Lock is on, the Times key acts as a multiplication sign on the numbers entered. When Num Lock is off, the Times key types a *. Times The Page Down key is a navigation key, which will drop the displayed area down the page one screen's worth. It doesn't necessarily move a whole literal page at a time. Page Down That would depend on the height of a page. The Page Up key is a navigation key, which will move the cursor up the displayed area one screen's worth. It does not usually move a literal page at a time. That would Page Up depend on the height of a page. The Pause key is little used under Windows. Under DOS it is used to halt actions in progress, often so that messages on the screen can be read before they scroll off Pause the screen. The Print Screen key is more useful under DOS than under Windows. Under DOS pressing the Print Screen key immediately sends the contents of the screen to the Print Screen printer. 9
  11. 11. The American University in Cairo Introduction to Computers Academic Computing Services Under Windows pressing the Print Screen key sends a copy of the screen to the Clipboard. You must then paste to an appropriate program and print from there. The Scroll Lock key is more useful under DOS where pressing it will stop text on the screen from scrolling off the top of the screen. This gives you time to read or print Scroll Lock it before continuing. When Num Lock is on, the Slash key acts as a division sign on the numbers entered. When Num lock is off, the Slash key types a /. Slash Spacebar The Spacebar is used to enter blank spaces in text. Sometimes it can also be used instead of a mouse click on buttons. The Tab key is used to move the cursor over to the right to a pre-set point. This is especially used in word processing to line up text vertically. Tab 10