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Personal computer Systems
When you mention the word “technology”, most people think about computers. Virtually every facet of our lives has some computerized component. The appliances in our homes have microprocessors built into them, as do our televisions. Even our cars have a computer. But the computer that everyone thinks of first is typical the personal computer ,or PC.
A PC is a general-purpose tool built around a microprocessor. It has lots of different parts--memory, a hard disk ,a modem ,etc.—that work together. “General purpose” means that you can do many different things with a PC. You can use it to type documents, send e-mail, browse the Wed and play games. On the Inside
Let us take a lood at athe main components of a typical desktop computer.
Central processing unit(CPU)—The microprocessor “brain” of the computer system is called central processing unit. Everything that a computer does is overseen by the CPU.
Memory—This is very fast storage used to hold data. It has to be fast because it connects directly to the microprocessor. There are sever specific types of memory in a computer:
Random-access memory(RAM)—Used to temporarily store information that the computer is currently worling with
Read-only memory(ROM)—A permanent type of memory storage used by the computer for important data that does not change
Basic input/output system(BIOS)—A type of ROM that is used by the computer to establish basic communication when the computer is first turned on.
Caching—The storing of frequently used data in extremely fast RAM that connects directly to the CPU
Virtual memory—Space on a hard disk used to temporarily store data and swap it in and out of RAM as needed
Motherboard—This is the main circuit board that all of the other internal components connect to. The CPU and memory are usually on the motherboard. Other system may be found directly on the motherboard or connected to it through a secondary connection. For example, a sound card can be built into the motherboard or connected though PCI.
Power supply—An electrical transformer regulates used by the computer .
Hard disk—This is large-capacity permanent storing used to hold information such as programs and documents.
Operating system—This is the basic software that allows the user to interface with the computer.
Integrated Drive Electronics(IDE)Controller—This is the primary interface for the hard drive, CD-ROM and floppy disk drive
Peripheral Component Interconnect(PCI) Bus—The mostr common way to connect additional components to the computer, PCI uses a series of slots on the
motherboard that PCI cards plug into .
SCSI—The small computer system interface is a method of adding additional devices, such as hard drives or scanners, to the computer.
AGP—Accelerated Graphics Port is a very high-speed connection used by the graphics card to interface with the computer.
Sound card—This is used by the computer to record and play audio by converting analog sound into digital information and back again.
Graphics card—This translates image data from the computer into a format that can be displayed by the monitor. Connections
No matter how powerful the components inside your computer are ,you need a way to interact with them. This interaction is called input/output(I/O). The most common types of I/O in PCs are
Monitor—The monitor is the primary device for displaying information from the computer.
Keyboard—The keyboard is the primary device for entering information into the computer.
Mouse—The mouse is the primary device for navigating and interacting with the computer
Removable srorage—Removale storage devices allow you to add new information to your computer very easily, as well as save information that you want to carry to a different location
Floppy disk—The most common form of removable storage , floppy disks are extremely inexpensive and easy to save information to .
CD-ROM—CD-ROM(compact disc, read-only momory) is a popular form of distribution of commercial software. Many sysrems mow offer CD-R (recordable) and CD-RW(rewritable), which can also record .
Flash memory—Based on a type of ROM called electrically erasable programmable read-only memory (EEPROM), Flash memory provides fast, permanent storage. Compact Flash, Smart Media and PCMCIA cards are all types of Flash memory.
DVD-ROM—DVDROM is similar to CD-ROM but is capable of holding much more information Ports
Parallel—This port is commonly used to connect a printer. Serial—This port is typically used to connect an external modem.
Universal Serial Bus (UBS)—Quickly becoming the most popular external connection, UBS ports offer power and versatility and are incredibly easy to use
Fire-Wire(IEEE1394)—Fire-Wire is a very popular method of connecting digital video devices, such as camcorders or digital cameras, to your computer. Internet/network connection
Modem—This is the standard method of connecting to the Inernet
Local area network(LAN) card—This is used by many computers, particularly those in an Ethernet office network, to connected to each other.
Cable modem—Some people now use the cable-television system in their home to connect to the Internet
Digital Subscriber Line(DSL) modem—This is a high-speed connection that works over a standard telephone line
Very high bit-rate DSL(VDSL) modem—A newer variation of DSL, VDSL require that your phone line have fiber-optic cables. From Powerup to Shutdown
Now that you are familiar with the parts of a PC, let us see what happens in a typical computer session, from the moment you turn the computer on until you shut it down.
You press the “On” button the computer and the monitor.
You see the BIOS software doing its thing , called the power self-test(POTS). On many machines, the BIOS displays text describing such data as the amount of memory installed in your computer and the type of hard disk you have .During this boot sequence, the BIOS does a remarkable amount of work to get your computer ready to run.
The BIOS determines whether the video card is operational. Most video cards have a miniature BIOS of their own that initializes the memory and graphics processor on the card. If they do not ,there is usually video-driver information on the another ROM on the motherboard that the BIOS can load
The BIOS checks to see if this is a cold boot or a reboot. It does this by checking the value at memory address0000:0472.A value of 1234h indicates a reboot, in which case the BIOS skips for the rest of POST. Any other value is considered a cold boot
If it is a cold boot , the BIOS verifies RAM by performing a read/write rest of each memory address, it checks for a keyboard and a mouse. It looks for a PCI bus and , if it finds one , checks all the PCI cards . If the BIOS finds any errors during the POTS, it notifies you with a series of beeps or a text message dosplayed in the screen. AN error at this point is almost a hardware problem.
The BIOS looks at the sequence of storage devices identified as boot devices in the COMS Setup. “Boot” is short for “bootstrap”, as in the old phrase “Lift yourself up by your bootstraps.” Boot refers to the process of launching the operating system. The BIOS tries to initiate the boot sequence from the first device using the bootstrap loader.
The bootstrap loader loads the operating system into memory and allows it to begin system, user information and applications. The bootstrap loader then establishes the data structures that are used to communicate within and between the sub-system and application of the computer .Finally, it turns control of the computer over to the operating system.
Once loaded , the operating system’s tasks fall into six broad categories:
? processor management—breaking the tasks down into manageable chunks and priotitizing them before sending to the CPU.
? Memory management—coordinating the flow of data in and out of RAM and determining when virtual memory is necessary.
? Device management---providing an interface between each divice connected to the computer,the CPU and applications
? Storage management—Directing where data will be stored permanently on hard drives and other forms of storage .
? Application interface--Providing a standard communications and data exchange between software programsand the computer.
? User Interface---providing a way for you to communicate and interact with the computer.
When you choose the “shut down”option, the opreating system closes all programs that are currently active. If a program has usaved information,you are given an opportunity to save it before closing the program.
The operating system writes its current settings to a special configuration file so that it will boot up next time with the same settings. If the computer provides software control of power, then the operating system will completely turn off the computer when it finishes its own shut –down cycle. Otherwise, you will have to manuslly turn the power off.