Computer Fundamental (part 2)

CPU [Central Processing Unit]

Though the term relates to a specific chip or the processor a CPU's performance is determined by the rest of the computers circuitry and chips.

Currently the Pentium chip or processor, made by Intel, is the most common CPU though there are many other companies that produce processors for personal computers. One example is the CPU made by Motorola which is used in Apple computers.

With faster processors the clock speed becomes more important. Compared to some of the first computers which operated at below 30 megahertz (MHz) the Pentium chips began at 75 MHz in the late 1990's. As of mid 2003 speeds now exceed 3000+ MHz or 3 gigahertz (GHz) (check your local computer store for the latest speed). It depends on the circuit board that the chip is housed in, or the motherboard, as to whether you are able to upgrade to a faster chip. The motherboard contains the circuitry and connections that allow the various components to communicate with each other. Output Devices An output device is a piece of hardware (a key physical part of a computer that can be touched) which a machine, typically a computer, uses to present information to the user. It can show any amount of information and any kind of information; for instance: sound, data, memory, images etc... Common output devices include Earphones, Projectors, computer displays, printers and speakers. Some of Devices are: • Monitor • Speaker & Other voice output devices • Printer • Plotter Monitor A computer display is also called a display screen or video display terminal (VDT). A monitor is a screen used to display the output. Images are represented on monitors by individual dots called pixels. A pixel is the smallest unit on the screen that can be turned on and off or made different shades. The density of the dots determines the clarity of the images, the resolution. Speaker Speaker is normally used by a PC user to listen sound ie music etc. Other voice output devices This device produces a human speech like sound, but actually is prerecorded vocalized sounds. Voice output is used in the telephone information system, where the requested number is reported using a voice output system. For example, when dial to customer care from your mobile for Recharge [for example], you hear voice output upon your request. Voice output is becoming common in voice messaging systems. Printer A printer is an output device that produces a hard copy of data. The resolution of printer output is expressed as DPI. Printers can be classified into different types in several ways. Personal Computer user use five kinds of printers: Daisy-Wheel Printer Daisy-Wheel is a printer mechanism that uses any kind of hub (wheel) having a set of spokes at the margin of the hub. The wheel can be removed to use a different character set. The end of each spoke is a raised image of a type character. When the wheel is turned and the required character is aligned to the print hammer, the character is then struck into a ribbon and onto a paper with the hammer. Chain Printer A chain printer uses a printing mechanism that uses character typefaces linked together in a chain. The chain spins horizontally around a set of hammers aligned with each position. When the required character is in front of the selected print position, hammer in that position hits the paper into the ribbon against the character in the chain. This printer is not commonly found around microcomputers, because it is a very expensive, high-speed machine designed originally for mainframes and minicomputers. Chain printers are very reliable and can speed up to 3000 lines per minute. Dot-Matrix Printer Dot-matrix printers are printers that write characters and form graphic images using one or two columns of tiny dots on a print head. The dot hammer moving serially across the paper strikes an inked-ribbon and creates images on paper. Dot matrix printers are popular printers used with microcomputers, because the printers are highly reliable and inexpensive. They are used for tasks where a high-quality image is not essential. Many users, however, move from dot printers to laser printers, because the price of laser printers is falling down. Several kinds of dot matrix printers are available with print heads that have 7, 9, 18, or 24 pins. Ink-Jet Printer Ink-jet is a printer mechanism that sprays one or more color of ink at high speed onto the paper and produces high-quality printing. This printer also produces color printing as well as high-quality image. That is, ink-jet printers can be used for variety of color printing at a relatively low cost. Ink-jet printing has two methods: Continuous stream method and drop-on- demand method. Laser Printer A laser printer is a printer that uses the electrophotograpic method used in a copy machine. The printer uses a laser beam light source to create images on a photographic drum. Then the images on the drum are treated with a magnetically charged toner and then are transferred onto a paper. A heat source is usually applied to make the images adhere. The laser printer produces high-resolution letters and graphics quality images, so it is adopted in applications requiring high-quality output. Although a high-priced color laser printer is also available in the market, a less expensive, desktop gray scale laser printer is widely used. Recently, the laser printer is gaining its market share dramatically, mainly because the lowered price and the quality. Plotter A plotter is a special-purpose output device that draws images with ink pens. That is, the plotter is a graphics printer for making sophisticated graphs, charts, maps, and three-dimensional graphics as well as high-quality colored documents. It can also produce larger size of documents. Plotters require data in a vector graphics format that can produce images with a series of lines. Plotters are used to produce high quality Images. BUS A BUS is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. Unlike a point-to-point connection, a bus can logically connect several peripherals over the same set of wires. Each bus defines its set of connectors to physically plug devices, cards or cables together. Why they are called “BUS”? They are called bus caz they are used for transferring data etc in computer architecture. Types of BUS: • Data BUS • Address BUS • Control BUS Data BUS Data Bus is used by CPU for transferring data. Address BUS An address bus is (part of) a computer bus, used by CPU units for communicating the physical addresses of computer memory locations that the requesting unit wants to access (read/write). Control BUS A control bus is used by CPU for communicating with other devices within the computer. While the address bus carries the information on which device the CPU is communicating with and the data bus carries the actual data being processed, the control bus carries commands from the CPU and returns status signals from the devices, for example if the data is being read or written to the device the appropriate line (read or write) will be active (logic zero). Memory Memory can be very confusing but is usually one of the easiest pieces of hardware to add to your computer. It is common to confuse chip memory with disk storage. An example of the difference between memory and storage would be the difference between a table where the actual work is done (memory) and and a filing cabinet where the finished product is stored (disk). To add a bit more confusion, the computer's hard disk can be used as temporary memory when the program needs more than the chips can provide. Types of Memory • Primary Memory/Storage • Secondary Memory/Storage Primary Storage Primary is directly connected to the central processing unit of the computer. It must be present for the CPU to function correctly, just as in a biological analogy the lungs must be present (for oxygen storage) for the heart to function (to pump and oxygenate the blood). Primary Storage is also called temporary storage; Bcaz data stored on it got erased as we switch off the computer. Primary storage typically consists of two kinds of storage: • Main memory contains the programs that are currently being run and the data the programs are operating on. In modern computers, the main memory is the electronic solid-state random access memory [RAM]. • Registers are internal to the central processing unit. Registers contain information that the arithmetic and logic unit needs to carry out the current instruction. Secondary Storage Also known as Permanent Storage caz data stored onto it is permanent. It is used to store data that is not in active use. Secondary storage, or external memory, is computer memory that is not directly accessible to the central processing unit of a computer, requiring the use of computer's input/output channels. Secondary Storage devices: Hard Drive Also located inside the system case, the hard drive is the component which contains the operating system of the computer (i.e. Windows 98 or XP), software applications (i.e. Quicken or Microsoft Word), and all files (i.e. documents and photographs) on a hard disk. A hard drive stores this data during and between the times one uses the computer. Hard drive These devices can both read and write data on the hard disk. The capacity of data storage for hard drives is measured in gigabytes. Hard drives capable of holding up to 200 gigabytes of information are now available for consumers to purchase. Most computers available today come with a 20, 40, 60, or 80 gigabyte hard drive. Hard drive Floppy Disk Drive Although it is completely contained within the system case, the opening of the floppy disk drive is usually visible in the front of the case. A floppy disk can be used to transfer information from one computer to another, install new software, or back up a small amount of files. This is accomplished by temporarily inserting the floppy disk into the disk drive. Floppy disk drive on front of the system case The picture below is a 3½ inch floppy disk which has a data storage capacity of 1.44 megabytes. Most computers made within the past 10 years have this type of floppy disk drive as a standard device. These disks can be read or written to by almost any computer and can be erased and reused over and over. 3 1/2 inch floppy disk The picture on the left is a 5¼ inch disk. These disks were commonly used during the 1980's when home computers were made available to the average consumer. 5¼ inch disk Because they are physically flexible, they were given the name floppy disks. The 5¼ inch disk is now considered to be outdated technology, and they are rarely used today because most modern computers do not even come equipped with that type of disk drive. Compact Disc Drive The compact disc is another way in which data can be stored, transferred, or installed. These discs are capable of holding up to 700 megabytes of information and are read by an optical device called the CD-ROM (Compact Disc - Read Only Memory) drive. As the name implies, a CD-ROM drive may only read or use the data on a compact disc. This device does not have the capability of placing information on a blank CD. Compact disc (CD) However, in recent years, a new type of compact disc drive has been made available to consumers. The CD-RW (Compact Disc - Read Write) drive not only allows one to use existing information on a CD but also to place data on a blank compact disc. Because of the optical process involved, this is commonly known as burning a CD and the CD-RW drive is often referred to as the CD-burner. CD-RW Memory Unit Computer data is in what is called binary format. This means that it is always a 0 or a 1. It only has these two states and must be in one of them. There are several fundamental data units which include: • Bit: A data unit which must be in one of the two binary states described above. It is the smallest data unit that exists. • Byte: 8 bits of data which has a possible value from 0 to 255. 8 bit (1/0) : 1 Byte [1 character] 1024 bytes : 1 kilobyte 1024 KB : 1 megabyte 1024 MB : 1 Gigabyte 1024GB : 1 Terabyte. Computer Data Computer data is raw information required by the computer to be able to operate. It is used to: • Run programs- This is the actual executable program data that the computer will execute to run the program such as Microsoft Word. • Store program or system configuration information. • Store information that the computer user needs such as text files or other files that are associated with the program the computer user is running. A common example of a program the computer user is running is the Microsoft Office suite of products which include Microsoft Word, Microsoft Excel, and others. These programs are also known as applications. Files & Folders Files Once you have typed or created a new document or file on your computer, you will have to decide what to do with it. You could print it right away using a Print command and then Exit or Quit your program without saving it, but most of the time you will want to save your document for future use. The computer saves its information on a disk, most often the hard disk, and the users determines where and when the file or document is saved. A computer file is a piece of arbitrary information, or resource for storing information, that is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished. Folders & Directories On the disk are directories or collection of folders. These directories or folders could be compared to a filing cabinet. All files are stored in a directory. Most hard disks have many directories or folders and files can be stored in any of them. Directories can have sub-directories and sub-sub-directories many levels down. The directory immediately below the current directory is called the child directory. The directory immediately above the current one is called the parent directory. The top of the directory structure is called the root directory. When a user adds or installs a new program on the computer the installation process will usually create a new directory or folder to store the application's files. Users can create and delete directories or folders as the need arises. Older version of DOS require that the directory be emptied of files before it can be deleted. When removing a directory always check before deleting it to make sure that it doesn't contain files you need. You can easily move files from one folder or directory to another using menu commands, drag & drop using the mouse or a file utility. It is important to understand your computer's directory structure as a file can be misplaced if it is saved in the wrong directory. One of the main problems new users have is creating a filing system. Modern operating systems address the 'filing problem' by automatically creating a (My) Documents folder. By saving files or documents in this folder you will always know where to look for your files. Create sub-folders within this folder for your main projects. Examples could be a separate folder for your correspondence called Letters or a folder for images called Graphics or Pictures. The main Documents folder can also be renamed to what every name you want it to be called. If you are not using Windows 9x simply create your own folder and sub-folders to save your documents in. Saving Files or Documents In order to save a new document or file you must first choose the Save command. Most modern software places this command in a menu which you access with the mouse button or Alt key. Each file must be given a filename so it can be found easily the next time it is needed. Computers using DOS 6.X or older must follow the 8.3 rule: a filename can only be 1 to 8 characters long followed by a 1 to 3 character extension separated by a dot (period or full stop). Modern operating systems allow computer users to use filenames up to 256 characters. Mac users, Windows 9X & NT/2000 and UNIX/LINUX use long file names but names using over 32 characters get unwieldy. It is better to use a directory or folder to help describe them and keep common files together. Many modern software programs (applications) add their own extension to filenames. These extensions allow operating systems to recognize certain filenames and associate them to the program that created it. As well as choosing a filename, users must choose a directory and/or disk to store the file in. Make sure that you are consistent and use a logical structure. Once you are sure you know where the file is going to be stored press Enter on the keyboard or press the left mouse button over the word Save or Okay to store the document on a disk, in the directory with the filename you have chosen. Some software programs will automatically save files in specific directory that is created when the program is installed (default settings). You can easily changed these settings permanently using the applications Preferences or temporarily at the point of saving the file. Some common rules are: • All files are saved on a disk or storage device. • A disk is usually broken up into directories and sometimes into partitions • A directory or folder is a way of keeping like files in a common area. A partitioned disk, though physically a single disk, is treated like separate disks and given a separate drive letter (and/or name). It is possible to save or move files anywhere that your computer can access. This includes disk (or other storage devices) on your computer, to any directory or sub-directory on your computer or on a network that your computer is connected to. Always make sure that you have chosen the correct directory and filename before pressing Enter or choosing Save. Printing The promise of a paperless office has not happened though conservation is catching on and it is possible to reduce paper consumption by using your computer more effectively. Having said that many computers are attached to printers and there are many reasons to print out documents that you create on your computer. Most software programs and applications allow the user to print the information that is created in the program. When choosing a printer consider the peripheral equipment that you will need as well as the actual printer. Peripherals include paper, ribbons or ink cartridges, toner and occasionally print heads. Backup & Disk defragmenter Defragmentation In the context of administering computer systems, defragmentation (or defragging) is a process that reduces the amount of fragmentation in file systems. It does this by physically reorganizing the contents of the disk in order to store the pieces of each file close together and in order (contiguously). It also attempts to create larger regions of free space using compaction to impede the return of fragmentation. Some defragmenters also try to keep smaller files within a single directory together, as they are often accessed in sequence. Backup Backup refers to the copying of data so that these additional copies may be restored after a data loss event. Backups are useful primarily for two purposes: 1. To restore a computer to an operational state following a disaster (called disaster recovery) 2. To restore small numbers of files after they have been accidentally deleted or corrupted. Backups differ from archives in the sense that archives are the primary copy of data and backups are a secondary copy of data. Backup systems differ from fault-tolerant systems in the sense that backup systems assume that a fault will cause a data loss event and fault-tolerant systems assume a fault will not. Backups are typically that last line of defense against data loss, and consequently the least granular and the least convenient to use. Since a backup system contains at least one copy of all data worth saving, the data storage requirements are considerable. Organizing this storage space and managing the backup process is a complicated undertaking. Backing up Files Computer errors and software failures happen ocasionally so it is important to backup your files and documents. One simple way to backup your files is to copy them to a disk. If there are only a few small files a floppy disk will work but if you are backing up lots of large files a cd burner, a second hard drive or tape backup may be needed. You can use a software program to automate backups or do it manually. A manual backup usually involves dragging the files or folders to the backup disk or tape to create the duplicate backup. Store your backup files in a safe place out of the sun and away from electro-magnetic devices such as speakers and wires with strong electrical currents. Every file that you create and plan to keep should be backed up. This includes word processing documents, financial information, databases, photos, etc... Some less obvious files that also need to be backed up are email, Internet Favorites or Bookmarks, and Address Books. Check the help files in your email program on how to back up email. Generally each folder name in your email program is a file containing the individual email messages and copying these files to the backup disk or tape will be sufficient. Software preferences such as customized menus and settings can also be backed up. Check your software's help files to find out where these files are located. A newer software version may be installed on the computer before ever needing the backups so make sure that the newer programs can handle the older file format. When to backup is an individual choice. A company should have a backup policy which explains how and when data should be backed up. It all depends on how important the information is and how difficult it would be to duplicate it in the event of a system failure. If the information is critical an automatic backup system that duplicates the documents immediately may be needed (a Redundant Arrays of Inexpensive Disks (RAID) system is an example). If the files are not critical a weekly backup may be all that is needed. It is impossible to determine when a system failure will occur so it is better be cautious. The backed up data can then be used as an archive, to recover from a system failure or to transfer data to a new computer system. Simply copy the files to the correct folder to restore them. Backup software will have an automatic recovery feature that will restore the backed up file automatically. Compression and Decompression Most software you buy or get off the Internet is compressed. Computers store information in bytes which are made up of on or off signals. The software applications that uses these files need to have all the on and off signals (bytes) in place but when the file is stored they can be modified to take up less space on the storage disk or tape. There are commercial and shareware programs that will compress and decompressed files for you. The most popular form of data compression is called zip or stuffit but there are others available as well. Programs are also available to compress and decompress your files as you or the application you are using requires them. This can be a way of making more space available on a hard drive. Windows comes with a program that will compress part of your hard disk. Be sure to read the documentation before embarking on a project like compressing a hard drive.