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What are the Keyboard Function(computing)

Monday, January 12, 2009

In computing, a keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, which act as electronic switches. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.

In normal usage, the keyboard is used to type text or numbers into a word processor, text editor or other program. In a modern computer, the interpretation of keypresses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using special gaming keyboards, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine.

Along the top of your keyboard is a row of keys numbered F1 to F10 or F12. Even though you may never use them, they do have function. In fact, the F stands for Function and they are called Function keys.

Below is a list of what each key does. After the list is a trick that you can use Function keys for. Most of the items on the list below apply only to Windows and Windows' programs, especially Windows Explorer and Internet Explorer.

Some programs have their own set of functions that they have assigned to the Function keys. You can find these in the menu of the program. The menu items which are assigned a function key have the corresponding function key designated after the item name. If you press that function key, you can perform that function without using the menu or buttons. The program's help or manual should also tell which functions are assigned to the function keys. You might want to try each one of these as you read through them.

Function Keys for Windows

* F1 - Opens Help for the currently displayed program (this does not work on all programs).

* Windows Logo key and F1 - Opens Windows' Help.

* F2 - Highlights the name of a selected object for renaming in Windows Explorer, desktop, and some other Windows' programs. First, you need to select an item that can be renamed (like, a file or shortcut). After pressing F2, you can then type what you want to rename the object to.

* F3 - Brings up Search in Windows Explorer.

* F4 - Drops down the Address bar in Internet Explorer showing your previous locations. This allows you to scroll down and select one.

* Alt and F4 - Closes the currently displayed program.

* F5 - Refreshes the view in Windows Explorer, Internet Explorer (in other words, it looks at the source again and reloads the contents), and other programs. In MailWasher it checks the mail (which I guess would be a kind of refresh).

* F6 - moves the cursor around the structure of a program. Pressing it may cycle you from window to window or from place to place within the program. In Windows Explorer it moves you from the left pane to the right pane and back. This is similar to what the Tab key does.

* Alt and F6 - Switches between multiple windows in the same program (for example, when the Notepad Find dialog box is displayed, ALT+F6 switches between the Find dialog box and the main Notepad window).

* F7 - does not have any functionality in Windows. It may be used in individual programs.

* F8 - accesses Safe Mode if pressed at the right time while the computer is starting. Safe Mode is a trouble-shooting mode, which will start the computer with minimal drivers.

* F9 - does not have any functionality in Windows. It may be used in individual programs.

* F10 - Changes the focus to and from the menu. Pressing the Alt key will also do this. Once the focus is on the menu items, you can use the arrow keys to navigate to an item and the Enter key to select it.

* Shift and F10 - brings up the popup menu in Windows Explorer much like right clicking on an item does.

* F11 - Switches between regular screen mode and full screen mode. Full screen mode is like a maximized screen but with more screen space and less toolbar controls

* F12 - does not have any functionality in Windows. It may be used in individual programs.

You may have noticed that some of the Function keys are not used (F7, F9, F12) in Windows. That doesn't mean that they can't be used. You can assign them or any other key combination to quickly run programs that you frequently use. Here are instructions for doing that.

* Locate the shortcut of that program. The Start menu is a good place to find shortcuts (every icon in the Start menu is a shortcut). If the program doesn't have a shortcut, create one.

* Right click on the shortcut and select the Properties item from the popup menu.

* The Properties dialog will open. Go to the Shortcut tab.

* Put the curser in the Shortcut key textbox and press the Function key or key combination (like Alt + Ctrl + 2) which you want to use to start the program.

* The Function key name or key combination name will appear in the box.

* Click on the Apply button (or the OK button) and close the dialog.

After you have done this, whenever you press that Function key or key combination, that program will start. Please note that if you use a Function key or key combination that is already used by Windows or other programs, it will no longer work in Windows or the other programs as it used to and will instead start your program.

To disable this, follow the above instructions but press Backspace or Delete in the Shortcut key textbox.

The Function keys are there to make your life easier. Now you can start using them.

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Basic Computer Operations

Tuesday, January 6, 2009


How Computer Work



Input: Information and programs are entered into the computer through Input devices such as the keyboard, disks or through other computers via network connections or modems connected to the Internet. The input device also retrieves information off disks.


Output: Output Devices displays information on the screen or the printer and sends information to other computers. They also display messages about what errors may have occurred and brings up message or dialog box asking for more information to be input. The output device also saves information on the disk for future use.


Processing: The CPU or central processing unit is sometimes called the Control Unit and directs the operation of the input and output devices. The Coprocessor or the Arithmetic-Logic Unit does arithmetic and comparisons. The memory or RAM temporarily stores information (files and programs) while you are using or working on them. The BIOS or basic input/output system controls the dialogue between the various devices.



Keyboard Layout and Data Entry



ENTER or RETURN - Moves the cursor down one line and to the left margin. Enter also process commands such as choosing an option in a dialog (message) boxes and submitting a form.


DEL or DELETE - Deletes the character at cursor and/or characters to the right of the cursor and all highlighted (or selected) text.


BKSP or BACKSPACE - Deletes the character to the left of cursor and all hightlighted text.


SPACE BAR - Moves the cursor one space at a time to the right


SHIFT KEY - Use the shift keys to type capital letters and to type the upper character on keys with two characters on them


CAPS LOCK - Locks the keyboard so it types capital letters (a light goes on when caps lock is on)


TAB - Moves the cursor five spaces to the right (number of spaces are usually adjustable). Tab moves to the next field in a form or table (Shift-Tab for previous field).


ESC or ESCAPE - Cancels a menu or dialog box


ARROW KEYS - Moves the cursor around document without changing text


FUNCTION KEYS or F KEYS - Access commands by themselves or in combination with the three command keys; CTRL, SHIFT, and ALT



Command or Special Keys



Command keys normally do nothing on their own but work in combination with other keys. Each piece of software uses the command keys differently though there is a move to standardize some functions. The Control key or Ctrl is often used to access commands. The Alternative key or Alt is often used to access menus. The Shift key is used to type CAPITAL LETTERS. As well the command keys are all used to move through documents and edit text faster and easier. As well many computers have Special keys design specifically for the particular computer. Apple computers have the Apple keys and Macs have Command keys. Many keyboards now have a Windows key specifically for Windows 9x and newer systems. Many older computers also have special keys used for a variety of different functions.


Some Notebook or Laptop keys are left out because of space limitations and they usually have a Special function key which allows other keys to double for the missing ones.




Basic Typing Rules



Place one space between each word, after a punctuation mark and at the end of a sentence. Always start a sentence with a capital letter. Use capitals for names, addresses, provinces and countries, places, organizations, businesses, associations, schools, colleges, universities, days of the week, months, holidays, nationalities, ethnic groups and languages.


Learning the keyboard is the first step to learning computers. Learning involves practice. It really is as simple as that. There are two kinds of typing.


The first is called Touch Typing. The Touch Typist uses the Home Keys (asdf for the left hand and jkl; for the right) and all the fingers on both hands as well as the thumbs for the Space Bar while typing. There are many commercial and public domain programs that are designed to teach this method.


The other method is some times called 'Hunt and Peck' or depending on finger strength 'Search and Destroy'. This involves using one or more fingers on one or two hands to type. It is a perfectly acceptable way of using a computer and many people get along fine with this technique.

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Computer Applications with Security

Security, Privacy, and Ethics



Security


Computers can store both public and private data. You ensure that what is stored on your computer is secure you can use a password to protect the material. User names and passwords can also protect the information stored on a computer. When using the Internet, one should use caution when giving out personal information.



Information Privacy



Intellectual property is a product someone creates based upon his or her thoughts or ideas. Copyright laws exits to protect those who create an idea or product. When using computers, one must respect the property, rights, and privacy of others.


One of the problems related to privacy is the tendency to regard anything displayed on a computer screen as public information. Although most people, including students, would never pick up and read a document lying on someone else's desk, many people do not hesitate to read someone else's computer screen. As word-processing and other tool software becomes more and more common, we must extend the courtesy of privacy from written documents to material displayed on computer screens or stored on disks.



Ethics and the Information Age


Ethics are the standards of honest, morality, and fairness. These standards relate to using computers. One has a responsibility to respect the property, rights, and privacy of others in the way you use computers. Today in the Information Age, one must follow a code of ethics to respect others properties and others personal information.


The legal aspects of computing are complex and multilayered. Teachers can help society by practicing ethical computer use, avoiding software piracy, and providing direct instruction on ethical computing practices.

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Computer Applications in Education

Monday, January 5, 2009

Computer Applications in Education



Management


Computers are used in a variety of ways in the educational field. Computers can be used in school management such as budget, inventory, student records, communications, library circulation, and library public access catalog.



Learning and Instruction


Computer applications can be used in education for learning and for instruction. Instruction and learning can be divided into two major areas, teacher-centered instruction and student-centered learning.


Teacher-centered instruction examined the computer as the object of instruction as well as a tool of instruction and the management of instruction. It is subdivided into the categories of computer literacy, CAI, CMI, and design of teaching materials.


Student-centered learning views the computer as a tool for the student to use to create, access, retrieve, manipulate, and transmit information in order to solve a problem. Understanding the concept of the computer as an information tool relies on accepting the fact that the computer is a productivity tool for the student and the teacher alike.



Educational Research


Computers are used widely in educational research. Educational research includes functions relating to information gathering and processing. The teacher/researcher may examine student performance data in new and revealing ways. Bibliographic citations of studies performed by educators around the world can be acquired and perused from the desktop computer.

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Software -- General Information

Sunday, January 4, 2009


Application Software


Application software programs work with the operating system software to help you use your computer to do specific types of work such as word processing to type a letter.


    1. Used by people to solve general problems
      • Can be used to do more than one thing - adapted to a wide variety of tasks
      • Some common tasks done by general purpose application software
        • Planning
        • Writing
        • Record keeping
        • Calculating
        • Communicating
        • Drawing
        • Painting
      • What can be done with general purpose application software is only limited by the imagination of the user.

    2. Examples of general purpose application software
      • Word Processing Software

      • Database Software

      • Spreadsheet Software

      • Desktop Publishing Software

      • Paint and Draw Software



Utilities


Utilities allow you to complete certain tasks on your computer. Examples of some of these tasks are file organizations.


  • Specific purpose application software used to help a computer work better or to avoid problems.
  • Some utility programs are built into the operating system
    • Scandisk in the Windows operating system
    • Disk formatting software
  • Examples of utility programs
    • Anti-virus software
    • Disk maintenance software
  • File management programs
  • Security software

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Software -- General Information

Friday, January 2, 2009


How Software is Inputted Into Computer

  1. Built into the computer's circuits, the ROM chips.
  2. Loaded into the computer from a secondary storage device, like a floppy disk or hard disk drive.
  3. Typed in from the keyboard.
    • Usually need to use a programming language to create the software.
    • Rarely done by most computer users today.

System Software

System software is a type of program that acts like a conductor in an orchestra. It directs all the activities and sets all the rules for how the hardware and software work together. MS DOS and Microsoft Windows are examples of system software or operating system software.



Some System Software is built into the computer.

  1. ROM chips and BIOS.
  2. Helps to setup the computer and start it.


Operating Systems

  1. The operating system is usually located on a disk.
    • Can be on either the hard disk drive, a floppy disk, or CD-ROM disk.
    • Must be loaded into RAM before it can be used.

  2. Used by the computer's hardware to work with its parts.
    • Tells the computer how to:
      • display information on the screen.
      • use a printer.
      • store information on a secondary storage device.
    • The system software that controls peripherals are called drivers.

  3. An operating system works with application software.
    • Does basic tasks, like printing a document or saving a file
    • The operating system starts (launches) the application software so that it can be used.


User Interfaces

  1. The user interface is how the computer's operating system presents information to the user and the user gives instructions (commands) to the computer.

  2. There are two kinds of User Interfaces
    • Text Interface
      • Presents information to the user in the form of text.
      • Have to type in commands or select commands from a menu displayed as text on the screen.
      • Hard to use or learn, because the user must memorize and type in commands.
      • Examples:
        • MS-Dos (MicroSoft Disk Operating System)
        • ProDos (Professional Disk Operating System)
      • Many of the Text Interfaces had shells placed over them.
        • A shell was more of a Graphic User Interface.
        • Made using the Text Interface easier to use.
    • Graphic User Interface (GUI)
      • Presents information to the use in the form of pull-down menus and icons.
        • Pull-down menus the user clicks on to display the menu
        • Icons are small pictures that stand for something, like a file, volume, trash, or program
      • The user gives commands to the computer by selecting items from a menu or by clicking on an icon when using a pointing device.
      • GUIs are easy to learn and use
      • Examples:
        • Windows 98
        • Windows 2000
        • MacOS

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Software -- General Information

Thursday, January 1, 2009



Computer software provides instruction that tell the computer how to operate.

    1. Software are also called programs.
    2. Programs are usually created using other software called programming languages.


There are two (2) main types of software



  1. System Software
    • Used by the computer to accomplish a task.
    • What system software does:
      • controls the internal function of the computer
      • controls other devices connected to the CPU

  2. Application Software
    • Used by people to accomplish a specific task.
    • Some common kinds of application software
      • Word Processor software
      • Database software
      • Spreadsheet software
      • Games
      • Web Page Browsers


Kinds of Software

  1. Public Domain Software
    • Has no copyright - no one owns the right to control who can make copies of the software.
    • Free to use or make copies of.
    • Can be copied, used in other programs, or changed by anyone.

  2. Freeware
    • Has a copyright - someone owns the right to determine who can make copies of the software.
    • Free to use and make copies of.
    • Can only give away exact copies of the software.
    • Can not be changed or used in another program without the copyright holder's permission.

  3. Shareware
    • Has a copyright.
    • Allowed to use the software before paying for it.
      • Can be a demo - which limits some major features like the Save command.
      • Can set an amount of time you can use the software.
      • Can trust that you will pay for it if you like the software.
    • Can only give away exact copies of the software.
    • Can not be changed or used in another program without the copyright holder's permission.

  4. Commercial Software
    • Has the most resistive copyright.
    • Have to buy the software before you can use it.
    • Can usually make one copy of the software as a backup copy.
      • A backup copy is used in case something goes wrong with the original software.
      • Can not give away or sell the backup copy.
    • Can not copy, look at the program's code, change, or use the software in another program without the copyright holder's permission.
    • Commercial Software is the best software in the world.

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Computer Hardware Details

Wednesday, December 31, 2008


This following list represents a basic set of hardware found in most PCs.


1. PC Case
2. Motherboard
3. Power Supply
4. Hard Disk Drive (HDD)
5. Floppy Disk Drive (FDD)
6. Compact Disk Drive (CDD)
7. Digital Video Disk drive (DVD)
8. Monitors (CRT and LCD)
9. Keyboard
10. Mouse
11. Audio
12. Cables & Wires

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PC Hardware Cont.............


More About Memory



RAM memory is installed in the system on little circuit boards called modules that plug into the motherboard. This makes it very convenient to add more memory by plugging in another module. Older computers used a SIMM, which stands for Single Inline Memory Module, and later ones use a DIMM or Dual Inline Memory Module. The difference is that DIMMs have different signals on each side of the module connector, and the additional signals allow more memory addresses and more data lines going in and out.


The amount of memory is always is some multiple of two bytes. The most common values are 32, 64, 128, 256 or 512 megabytes.


As it is used by the system, RAM is divided into base memory and extended memory. Base memory is the first megabyte, and extended memory is everything over that. The very first PCs had only base memory, and then a scheme was developed called expanded memory that tricked the computer into allowing more than 1 MB of memory. Once extended memory was developed though, expanded memory quickly became obsolete and will only be found in older computers.


Another memory term you will encounter is cache memory. This refers to memory that is not on DIMMs but is either built into the CPU or connected directly to the motherboard near the CPU. It provides even faster access than RAM for the data that the CPU expects to need next. The contents of the cache will change constantly depending on what the CPU is doing.

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PC Hardware Cont.............

Tuesday, December 30, 2008


The Motherboard


The biggest and most important circuit board in a computer is the motherboard. It's called the motherboard because every other part of the computer is connected to it. The CPU plugs into the motherboard, and so does the memory. And all the components that plug into the back of the case, like the keyboard and monitor, are connected from there to the motherboard. It is also called the system board.



There is a set of slots near the back edge of the board for plugging in other circuit boards, called adapter cards. These plug-in slots are for things like modems, sound cards, network cards and just about any other add-on feature you can think of. There is a set of traces connecting these slots to each other. A trace goes from Pin 1 of the first slot to Pin 1 of each of the other slots, and other traces connect each of the Pin 2s, each of the Pin 3s, etc. These traces then go on to connect to the memory, CPU, disk drives and other parts of the computer.



The Bus


These traces are called a bus, and they provide a way for each part of the system to exchange information with every other part. There are different types of bus that have been developed over the years, and your computer may have more than one. The most common one, found in every PC sold today, is called the PCI bus. An older version, still seen in some new computers, is the ISA bus. These are fairly easy to tell apart, because the connector that fits in the PCI slot has smaller pins and more of them.


One of the differences between PCI and ISA is that PCI supports a feature called Plug-and-Play, which allows you to add new hardware and have the system detect and configure it automatically. As anyone knows who has used the old method, plug-and-play is a great convenience.



Resources


Since just about everything in the computer uses the bus to exchange data, there must be a way to decide whose turn it is. This is done with something called an Interrupt Request, abbreviated IRQ. Each component or device that will need access to the bus is assigned an IRQ level, from IRQ 0 to IRQ 15, and there are lines on the bus that correspond to these levels. When a device needs to transfer data on the bus, it tugs on the appropriate Interrupt Request line and waits until the CPU grants an interrupt for that level. It's all very nice and orderly. IRQs are an example of a system resource, which is a feature available in limited quantity that must be assigned to specific components.


There are other resources too. Each device must have a unique memory location where their data is stored as it is transferred to and from the bus. These locations are called I/O Ports. For the BIOS and any other devices that use ROM, there must be a range of memory set aside, so that ROM and RAM are not trying to use the same addresses. These ROM addresses are a resource just like the IRQs and I/O Ports. Some devices need to transfer large amounts of data directly to and from memory without using an interrupt for each little piece of data. These devices, such as disk drives, are assigned a resource called DMA, for Direct Memory Access. Like IRQs, there are 16 DMA levels.

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PC Hardware Cont.............


More About Video



The monitor is a passive device that just displays the video output from the system. However, so much data is needed for the constantly changing screen display that special provisions are made for it.


The video card (or video circuitry on the motherboard) has its own RAM memory just to hold the display information, and its own ROM BIOS to control the output. Some motherboards even have a special high-speed connection between the CPU and the video. It’s called the AGP, or Accelerated Graphics Port.


The important numbers in evaluating a video display are how many distinct colors can be displayed and also the resolution, which is how many pixels the image contains across and from top to bottom. Each dot of color making up the image is one pixel. As video technology evolved there have been a number of standards, and each one has its own set of initials like EGA, CGA or VGA. A common one is SVGA, which stands for Super Video Graphics Array and has a resolution of 800x600 (that’s 800 pixels across and 600 down). Some high-performance monitors use SXGA (1280x1024) or even UXGA with a resolution of 1600x1200.


More About Disk Drives


Floppies – Although floppy drives are being phased out in some new computers, there are still millions of them out there and you should know something about them. The floppy drive has a little slot on the face of the computer cabinet, and into this slot you can slide a floppy diskette like the one shown here. One of the reasons floppy drives are still around is that it is very easy to take a floppy diskette from one system to another.


Inside the floppy diskette is a round flat disk coated with iron oxide on each side so that data can be stored on it magnetically. This disk is called a platter, and it spins underneath an electro-magnet called the write head that puts data onto the platter surface. There is another head called the read head that copies data from the platter.


Once the disk has made one complete revolution, data is written all the way around. That is called a track. The head then moves a bit and writes another circle of data to create a second track. Altogether, there are 80 tracks on each side, for a total of 160. Altogether, the floppy can hold 1.44 MB (megabytes) of data.


If we are looking for just a few bytes out of 1.44 million, it’s not enough to know which track it is in. To help narrow the search, the track is divided into 18 pieces, called sectors, which look much like a slice of pie. Each sector holds 512 bytes of data, so if we know the track and sector number of the data we want it won’t be hard to find.

Hard Drives – On a hard drive, data is also organized into tracks and sectors. While each sector still holds 512 bytes, there can be many more tracks and sectors on a platter. There are also multiple platters, one on top of the other like a stack of pancakes. Hard drives can hold much more data than floppies, sometimes into the billions of bytes, called gigabytes (GB).

Multiple platters require multiple read and write heads, all attached to the same arm so they move together. It’s called an actuator arm. When we are reading track number 10 on the top platter, the other heads are also positioned over track 10 of the other platters, and together all of these track 10s make up a cylinder. To specify the location of data on a hard drive it is necessary to say what cylinder, then the track and sector. Moving the heads from one cylinder to another is called a seek, and the amount of time this takes is the average seek time.


Although hard drives can hold much more data than floppies, the platters are sealed into a metal case that is fastened inside the computer cabinet, so it’s not an easy matter to move from one system to another like you can with floppies. A hard drive is sometimes called a fixed disk for this reason.


Operating systems use a couple of different methods to keep track of what data is stored where on a drive. One common method uses a table called a File Allocation Table or FAT, which is a section of the disk with pointers to data locations. There are two versions, called FAT16 and FAT32. Windows NT, XP and 2000 use a similar method called NTFS.


There are two different interfaces commonly by hard drives to talk to the rest of the system. These are called IDE for Integrated Drive Electronics, and SCSI for Small Computer System Interconnect. The technical differences are not important at this point, but you should know about the two types because they are not interchangeable.


Figuring out where the heads should go next and then moving them there is the job of some electronic circuitry called the disk controller. Every disk drive has its own controller, which may be on the motherboard or inside the drive itself, depending on the type of drive.


There are a few more things you should know about disk drives before we leave the subject. The first sector of Cylinder 0, Track 0 is called the boot sector, and it contains a Master Boot Record (MBR) that shows whether the disk contains an operating system and the location of the code. If there is more than one operating system, the drive must be divided into multiple partitions. If not, then the whole drive will be a single partition. All of the disk space assigned to a partition is called a volume.


Another term you will encounter is a disk format. There is a high-level format, which creates a new file allocation table and is done with a FORMAT command. There is also a low-level format that creates a new pattern of sectors. A low-level format must be followed by an FDISK command to create a new Master Boot Record and partitions.


Last, we have the word media. This refers to the actual surface holding the data, which is the platter in the case of a disk drive. Because the floppy platter can be taken out of the drive, it is called removable media, while a hard drive is called fixed media.


Other Drives – Most systems today, especially home systems, have additional storage drives that use CD or DVD discs. The technology for both is similar but DVDs hold much more data. These drives do not store data magnetically but use optical markings that are read with a laser. They are mostly used just to read data and not to write it. The full name for CD in fact is CD-ROM, which stands for Compact Disc - Read Only Memory. However, there are versions that can be used to write also, and these are called CD-RW and DVD-RW. Even so they are mostly used to write just once for permanent storage, and are not practical for constantly changing data.


Like hard drives, CD-ROM drives can use either an IDE or SCSI interface. The version of IDE for CD-ROM drives is called ATAPI, and for SCSI the CD-ROM version is ASPI.


Because the discs can be removed, CD-ROM and DVD are considered removable media. There are other types of removable media also that are not as common, such as tape drives and Zip disks, which are similar to floppies but with a storage capacity of 100 or 250 MB. Zip disks and tape drives also use the ATAPI interface.

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PC Hardware Cont.............

Monday, December 29, 2008


Ports



In addition to the I/O ports mentioned in the last section which are really addresses, there are physical connections on the back of the computer that are also called ports, and various devices connect to the computer through cables attached to these ports. One of these connections is called the Serial Port because data goes over a single signal line as a series of bits, one right after the other. Serial port connectors have either 9 or 25 pins, with the male connector on the back of the computer and a female connector on the cable. The 9-pin version is more common, and is often used to connect a mouse if there is not a separate mouse connection.


Another connection is called the Parallel Port because its cable has 8 parallel signal lines to transmit 8 bits at a time. The computer has a 25-pin female connector on the back, so it won’t be confused with the 25-pin male serial connector. The parallel port is most often used to connect a printer. Computers sold in the last few years will probably also have a connection called USB, for Universal Serial Bus. It is a bus because several devices can be connected on the same cable, but it’s also a port because data goes into and out of the computer cabinet through its connector. There is USB1 and USB2. USB2 is newer and much faster.




The BIOS



As we mentioned earlier, the computer knows what to do by taking instructions from programs stored in RAM. The main instructions come from a program called the operating system, and those instructions direct traffic for other programs called applications.



When the computer is turned off, all the instructions copied into the RAM are gone. When the system is turned on again, it needs to go out to the disk, get the operating system and load it into RAM, but there are no instructions in the RAM to tell it how to do this. The solution to this problem is a set of instructions that stay in memory and don’t get lost when the computer is turned off.


This set of instructions is called the BIOS, for Basic Input Output System. Since the instructions don’t need to change, they can be stored in a different kind of chip than we use for RAM. It’s called ROM, for Read Only Memory. We say that the instructions in the BIOS are hard-wired, and instead of software they are called firmware.


The computer goes through a process called booting up when it is first turned on. This involves executing the BIOS instructions, loading the operating system from disk into RAM, and then turning control of the computer over to the operating system after everything checks out OK. The term refers to somebody pulling themselves up by their own bootstraps (without outside help, in other words). Any computer term that includes ‘boot’ will have something to do with this start-up process.



CMOS and RTC



There is other start-up information that normally stays the same but that we might want to change once in a while. This includes info about the various pieces of hardware connected to the system, which disk drive to check first for the operating system and that sort of thing. This data can’t be stored on the hard drive because we need it to boot up. It can’t be stored in RAM because it will be lost at power-off, and it can’t be stored in the BIOS because we might need to change it.



The problem is solved by a type of RAM chip that uses very low power, and it is connected to a battery. This type of low-power memory chip is called CMOS. It stands for the type of technology used in the chip, which is Complementary Metal Oxide Substrate. This is probably more than you need to know, but I’m a fanatic about defining things. By the way, since batteries don’t last forever, if you leave your computer unplugged for about 5 years you’ll find it needs a bit of trickery to get it to boot again, because the CMOS information will be gone.



There is another feature in the computer that has the same requirements as CMOS, and that is the date and time function. This obviously needs to change very minute, but we don’t want to lose track when the computer is turned off. The circuitry for this is called the RTC or Real Time Clock, and for convenience it is usually included in the same chip with the CMOS. A little trickle of juice from the CMOS battery keeps the clock running, and when you turn the computer on again it knows exactly what time and day it is. Convenient, isn’t it?


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PC Hardware Cont.............

Sunday, December 28, 2008


The Motherboard



The biggest and most important circuit board in a computer is the motherboard. It's called the motherboard because every other part of the computer is connected to it. The CPU plugs into the motherboard, and so does the memory. And all the components that plug into the back of the case, like the keyboard and monitor, are connected from there to the motherboard. It is also called the system board.



There is a set of slots near the back edge of the board for plugging in other circuit boards, called adapter cards. These plug-in slots are for things like modems, sound cards, network cards and just about any other add-on feature you can think of. There is a set of traces connecting these slots to each other. A trace goes from Pin 1 of the first slot to Pin 1 of each of the other slots, and other traces connect each of the Pin 2s, each of the Pin 3s, etc. These traces then go on to connect to the memory, CPU, disk drives and other parts of the computer.



The Bus



These traces are called a bus, and they provide a way for each part of the system to exchange information with every other part. There are different types of bus that have been developed over the years, and your computer may have more than one. The most common one, found in every PC sold today, is called the PCI bus. An older version, still seen in some new computers, is the ISA bus. These are fairly easy to tell apart, because the connector that fits in the PCI slot has smaller pins and more of them.



One of the differences between PCI and ISA is that PCI supports a feature called Plug-and-Play, which allows you to add new hardware and have the system detect and configure it automatically. As anyone knows who has used the old method, plug-and-play is a great convenience.



Resources



Since just about everything in the computer uses the bus to exchange data, there must be a way to decide whose turn it is. This is done with something called an Interrupt Request, abbreviated IRQ. Each component or device that will need access to the bus is assigned an IRQ level, from IRQ 0 to IRQ 15, and there are lines on the bus that correspond to these levels. When a device needs to transfer data on the bus, it tugs on the appropriate Interrupt Request line and waits until the CPU grants an interrupt for that level. It's all very nice and orderly. IRQs are an example of a system resource, which is a feature available in limited quantity that must be assigned to specific components.



There are other resources too. Each device must have a unique memory location where their data is stored as it is transferred to and from the bus. These locations are called I/O Ports. For the BIOS and any other devices that use ROM, there must be a range of memory set aside, so that ROM and RAM are not trying to use the same addresses. These ROM addresses are a resource just like the IRQs and I/O Ports. Some devices need to transfer large amounts of data directly to and from memory without using an interrupt for each little piece of data. These devices, such as disk drives, are assigned a resource called DMA, for Direct Memory Access. Like IRQs, there are 16 DMA levels.

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PC Hardware Cont.............

Saturday, December 27, 2008


Software


The physical parts of as computer are called hardware. These are things you can see and touch, and yes, they are hard.


These same pieces of hardware are used whether you want to write a letter, balance your checkbook or play a game of computer solitaire, so how does this hardware know what to do, and when to do it? Actually, the hardware parts don't have a clue. They need instructions to tell them what to do, so some of that information we're storing and processing must be the instructions telling the computer what to do.



These instructions are called software, and they are organized into sets of instructions called programs. If you want to play a game on the computer, the computer must have a program with the instructions for that particular game. If you want to send e-mail, there must be an e-mail program.



One program called the operating system contains the instructions for actually running the computer. Certain things need to be done no matter what you are using the computer for. These are things like getting data on and off the disk, getting information to the monitor screen, and so forth. A program called Windows is the most common operating systems for PCs, and the one used in this office.It comes from a little company called Microsoft. Perhaps you have heard of it.



Anyway, the operating system takes care of the basic details of running the computer, and allows other programs to concentrate on their particular tasks. These other programs are called applications, because their job is to apply the computer to a specific task. When we say software, that can mean the applications, the operating system, or both.



There are other little chunks of software that attach to the operating system and tell it how to run particular hardware components or applications. These little chunks are called drivers, and anytime you add a piece of hardware to a system or upgrade to a new version of a device, you will need to have the right driver for that new piece of hardware.




Circuits


The word 'circuit' means a path something follows that goes back to where it started. In an electrical or electronic circuit, the thing following the path is of course electricity. Whatever work it does and whatever components it must go through on the way, the 'circuit' just means there is a complete path back to the starting point. The word 'circuitry' means the components, and the connections between them, that make up the path. It's as simple as that.



In a computer, this word 'circuit' shows up in a couple of places. Most of the components will be found soldered to a 'circuit board', also called a printed circuit board. This is a thin board of fiberglass, with the connections between components (called traces) printed right on the board in copper.



The components themselves are often something called an Integrated Circuit, abbreviated IC. To integrate means to combine things together, so an integrated circuit is one that combines many circuits into the same part. These are formed on a thin wafer or 'chip' of silicon, and you will sometimes hear an IC being called a 'chip'. This is also where we get the name 'Silicon Valley', for the area in Central California where many of them are made.



This chip of silicon is put into a case with metal legs, and tiny wires between the wafer and the legs connect those circuits with the outside world. There are now ICs containing millions of transistors and other components, all in a package that will fit in your palm with lots of room to spare.


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PC Hardware Cont.............

Friday, December 26, 2008


Output


There are a number of ways to get data back out of the computer. One of them is right there in front of your face, and that's the monitor. It has a screen that shows you information from the computer, so it is an output device. The monitor and the parts of the computer that run it are known as video. Another common output device is a printer, which of course puts the computer's output on paper for you.


Some devices are both input and output, like the floppy diskette mentioned earlier. If you have a modem or network connection, information can go both ways over the line so it's both input and output. In many cases it is practical to consider input and output together, in which case they are called Input/Output and abbreviated as I/O.




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PC Hardware Cont.............

Thursday, December 25, 2008


Storage

Information is stored in a computer in several different ways, but the main two are RAM and hard drive, also called a hard disk.

The hard drive can store huge amounts of information, and it can keep this information when the computer is turned off. The only problem with hard drives is that it takes too long to get the data from them, because the system must wait as the disk spins until the right part of the disk surface comes under the read heads, and then the drive transfers a block of data in sequence.

For information being used at the moment, the system needs to be able to get to any part of that information very quickly. The storage for this information is RAM, which stands for Random Access Memory. Random access means the system can ask for any piece of stored data at random and get it immediately, without waiting for to come up in sequence.

Random access is faster than sequential access. The main reason that computers don't just store everything in RAM is that information in RAM is lost whenever the power is turned off. So, the computer needs both RAM and disk storage. Everything stored long-term is on the disk, and whatever is needed at the moment is copied into RAM. If changes are made to the data in RAM, the changes must be copied back to the disk before that computer is turned off so those changes are not lost.

When people talk about the memory of a computer, they almost always mean RAM, and not the hard drive or other forms of storage that we haven't covered yet. Sometimes they will say 'main memory' just to be perfectly clear about it.

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PC Hardware Cont.............

Wednesday, December 24, 2008


Processing


If we just put information into the computer and took it out again later, computers could be much simpler. Most of the time though, we want to do something with it or change it in some way. Doing something with it is called processing, or data processing. Most of this takes place in a part called the processor, or Central Processing Unit. This is usually abbreviated to CPU.


The CPU is such an important part of the computer that we often refer to a system by the type of CPU it contains. My office computer is a Pentium III but at home I have an Athlon system. Sometimes you will hear the entire computer cabinet called a CPU.


To help the CPU there is another part that takes over a lot of the arithmetic. It is called the co-processor and also the Numerical Processing Unit or NPU.


The smallest piece of data that a computer can process is called a bit, and each bit will be either a one or a zero. For the sake of efficiency, the computer normally deals with a minimum of 8 bits at a time, and 8 bits together is called a byte. This is an important word to remember, because in working with computers you will hear about bytes frequently, and also megabytes which is one million bytes. Megabyte is usually abbreviated MB.


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PC Hardware

Tuesday, December 23, 2008



Basic Computer Hardware Information


This is a very short course about computers. It won't make you into a computer technician, but it will let you talk to one without thinking they are speaking a foreign language. The computers we are interested in are the general-purpose personal computers like we use at our desk, rather than the specialized computer under the hood of your car, or the big mainframe computers that the IRS uses to keep track of us all.


For our purposes, a computer can be defined as a machine for processing and storing information electronically. To be useful, it must have a way for us to get information into the machine, and some way to get it out afterwards so we can see it. Therefore, a computer has four basic functions:


1. Input
2. Processing
3. Storage
4. Output


Every part of a computer system, and everything it does, is connected to one or more of these basic functions. Computers can seem complex because there are many ways of doing each of these functions, and because everything has a new name, often made up of what appear to be nonsense initials like RAM or CPU.


To keep it simple, first look up any word or technical term you don't understand. There is a glossary at the back of this course pack with definitions for all the technical terms we use here or that you are likely to hear in talking to technicians. Second, when you encounter any part of a computer for the first time, find out which of these four functions it is used for.



Input


The most obvious device for getting information (also called data) into a computer system is the keyboard. Another common input device is the mouse. Almost any time we use a computer we use one or both of these to get text data or instructions into the system. To get large amounts of information into the computer we would probably use a CD (compact disc), a floppy diskette, a modem connected to a phone line, or a network card connected to a network.


With the right sound equipment, a microphone or musical instrument can be used to bring in sound, and a digital camera can download visual information, so these are all being used as input.



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Hardware


What is Hardware?

Hardware is best described as a device that is physically connected to your computer or something that can be physically touched. A CD-ROM, Monitor, Printer, and video card are all examples of computer hardware. Without any hardware your computer would not exist and software would have nothing to run on.

There are several differences between computer hardware and software. However, the fundamental difference between hardware and software is that hardware is a physical device something that you're able to touch and see. For example, the computer monitor you're viewing this text on or the mouse you're using to navigate is considered computer hardware.

Computer hardware is the physical part of a computer, as distinguished from the computer software or computer programs and data that operate within the hardware. The hardware of a computer is infrequently changed, in comparison with software and data which are "soft" in the sense that they are readily created, modified or erased on the computer. Firmware is special software that rarely, if ever, needs to be changed and so is stored on hardware devices such as read-only memory (ROM) where it is not readily changed

The image to the right is of a webcam, an example of an external hardware peripheral that allows users to make basic videos, transmit videos of themselves over the Internet, and take pictures.



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Software

What is software?


Software is the information stored on the computer.That is to say,Software is the programs, so programs and data are considered to be software. Basically, if you can email it to someone, it's software.

Software is a collection of instructions that enables a user to interact with the computer or have the computer perform specific tasks for them. Without any type of software the computer would be useless. For example, you wouldn't be able to interact with the computer without a software operating system. Almost all software purchased at a retail store is included in a box similar to the one shown to the right, this box usually contains all the disks (floppy diskette, CD, and/or DVD) required to install the program onto the computer, manuals, warranty, and other important documentation.




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