PC Systems and Components - System Case, Power, Motherboard and System Devices, The Processor, Read-Only Memory (ROM), Random Access Memory (RAM), Static RAM (SRAM), Dynamic RAM(DRAM), Video Card referat

Overview of PC Systems and Components


One of the great strengths of the PC platform that has led to its overwhelming success in the marketplace is its modularity. Most PCs are made up of many different individual components, which can be mixed and matched in thousands of different configurations. This lets you customize the PC you either buy or build to meet your exact needs.


This section discusses some of the major components of a typical, modern PC. Some PCs have some of these combined into one physical unit, but inside, somewhere, you'll find most if not all of these pieces.

System Case

The box or outer shell that houses most of the computer, the system case is usually one of the most overlooked parts of the PC. While it may seem inconsequential, the case actually performs several important functions for your PC, including protection for the computer circuits, cooling, and system organization. In addition, the system case is normally purchased together with the system power supply, and must also be matched with the size, shape and electrical requirements of your motherboard. Therefore, it has an impact on your options with these important components as well.



System Case

The system case, sometimes called the chassis or enclosure, is the metal and plastic box that houses the main components of the computer. Most people don't consider it a very important part of the computer (perhaps in the same way they wouldn't consider their own skin a very important body organ). While the case isn't as critical to the system as some other computer components (like the processor or hard disk), it has several important roles to play in the functioning of a properly-designed and well-built computer.




The case doesn't appear to perform any function at all, at first glance. However, this isn't true; the case is in fact much more than just a box. The case has a role to play in several important areas:

  • Structure: The motherboard mounts into the case, and all the other internal components mount into either the motherboard or the case itself. The case must provide a solid structural framework for these components to ensure that everything fits together and works well.

  • Protection: The case protects the inside of your system from the outside world, and vice-versa. Vice versa? Yes, although most people don't think about that. With a good case, the inside of your computer is protected from physical damage, foreign objects and electrical interference. Everything outside of your computer is protected from noise created by the components inside the box, and electrical interference as well. In particular, your system's power supply, due to how it works, generates a good deal of radio-frequency (RF) interference, which without a case could wreak havoc on other electronic devices nearby.

  • Cooling: Components that run cool last longer and give much less trouble to their owner. Cooling problems don't announce themselves; you won't get a "System Cooling Error" on your screen, you'll get random-seeming lockups and glitches with various parts of your system. You'll also have peripherals and drives failing months or years before they do on your friend's computer, and you'll never even dream that poor cooling is the cause. Making sure that your system is cooled properly is one good way to save yourself time, trouble and money.

Note: A spacious, well laid-out case is a critical part of proper system cooling. Small cases require components to be packed close together, which reduces cooling in two ways. First, air-flow through the case is reduced because it is blocked by the components. Second, the parts are closer together so there is less space for heat to radiate away from the devices that are generating it.

  • Organization and Expandability: The case is key to a physical system organization that makes sense. If you want to add a hard disk, CD-ROM, tape backup or other internal device to your PC, the case is where it goes. If your case is poorly designed or too small, your upgrade or expansion options will be limited.

  • Aesthetics: The system case is what people see when they look at your computer. For some people this isn't important at all; for others it's essential that their machine look good, or at least fit somewhat into their decor. In an office environment, PCs that all look different can give a work center a "hodge-podge" appearance that some consider unprofessional, for example.

  • Status Display: The case contains lights that give the user information about what is going on inside the box (not a lot, but some). Some of these are built into the case and others are part of the devices that are mounted into the case.

In terms of its actual operation, the case doesn't of course do a lot. It does have switches and the above-mentioned status lights.


Your computer is obviously an electronic device, and its many components of course require power. Like the case, most people don't give much thought to the power supplied to the system. The power supply in your PC can be compared to the officials at a football game: if they are doing their jobs properly nobody really notices them, but if they aren't, everybody knows it and lets them know about it.

There are two aspects to power in the PC:

  • External Power: External power refers to the power that is delivered to the back of the system case. There are several considerations regarding this power and how it is supplied that will determine if your internal power supply is going to work the way it should.

  • Power Supply: The power supply is the small box that sits inside your case and takes the external power you supply to the computer. Its main job is to transform this power into a form the rest of the computer can use.

The Power Supply

The internal power supply is responsible for converting your standard household power into a form that your computer can use. The power supply is responsible for powering every device in your computer; if it has a problem or is of low quality you may experience many difficulties with your PC that you may not realize are actually the fault of the electrical system. The power supply plays an important role in the following areas of your system:

  • Stability: A high quality power supply with sufficient capacity to meet the demands of your computer will provide years of stable power for your PC. A poor quality or overloaded power supply will cause all sorts of glitches that are particularly insidious, because the problems occur in other, seemingly unrelated, parts of the system. For example, power supplies can cause system crashes, can make hard disks develop bad sectors, or cause software bugs to appear, problems which can be very difficult to trace back to the power supply.

  • Cooling: The power supply contains the main fan that controls the flow of air through the PC case. This fan is obviously a major component in your PC's cooling system.

  • Energy Efficiency: Newer PC power supplies work with your computer's components and software to reduce the amount of power they consume when at a idle. This can lead to significant savings over older systems.

  • Expandability: The capacity of your power supply is one factor that will determine your ability to add new drives to your system, or upgrade to a more powerful motherboard or processor. If you build a new system with a power supply that barely meets your needs, you may have to replace it when you upgrade down the road.

Motherboard and System Devices

The motherboard is the base of the modern computer system. If the processor is the "brain" of the computer, then the motherboard is the "central nervous system and circulatory system", plus much more, all rolled into one. Here are the main parts of the motherboard and its related devices:

  • Motherboard (Abit BD7-II Intel 845E Socket 478 ATX): The motherboard is the main circuit board in the computer where everything comes together. This is where you plug in your processor, memory, cache, video card and other cards. It is also where you connect your peripherals.

  • System Chipset and Controllers: The chipset and other motherboard circuitry are the "smarts" of the motherboard. Their job is to direct traffic and control the flow of information inside the computer. These circuits control the processor's access to memory, the flow of data to and from peripheral devices and communications lines, and much more. The chipset is a critical part of any computer, because it plays a big role in determining what sorts of features the computer can support. For example, which processors you can use, which types of memory, how fast you can run the machine, and what kind of system buses your PC can use, are all tied in to the type of chipset the motherboard uses.

  • System Buses: The system buses are the electrical channels through which various parts of the computer communicate. The physical part of these buses, the part you see, is the set of slots in the back of the machine into which you put your video card, sound card and other cards. It is over the system buses that your video card gets information from the processor; the processor saves data to your hard disk, etc. The architecture chosen for each of the system buses have a great impact on the performance of your PC, as well as dictating your choices for video cards and other devices.

  • BIOS: The system BIOS (which stands for Basic Input/Output System and is pronounced "bye-oss") is a computer program that is built into the PC's hardware. It is the lowest-level program that runs on your computer. Its job is to act as an intermediary between your system hardware (the chipset, motherboard, processor and peripherals) and your system software (the operating system). By doing this, the operating system doesn't have to be made different for every machine, which is why DOS will load on any PC. The BIOS is what runs when you turn on your computer, and what loads your operating system. The BIOS also allows you to set or change many different parameters that control how your computer will function. For example, you tell the BIOS what sort of hard drives you have so it knows how to access them.

  • Cache: The system cache is a small, high-speed memory area that is placed between the processor and the system memory. The value of the cache is that it is much faster than normal system memory. Each time the processor requests a piece of data from the memory, the system first checks the cache to see if the information is there. If it is, then the value is read from cache instead of memory, and the processor can get back to work that much sooner. If it isn't, then the data is read from memory and given to the processor, but it is also placed into the cache in case the processor needs it again in the near future.

  • System Resources: System resources are not actual physical devices; they are nothing you can reach into the machine and touch. But they are very important for two reasons. First, they dictate how your PC organizes its access to various memory areas and devices. Second, they are one of the most common areas where people have problems with the setup of their PCs (resource conflicts). These are the four types of resources that various parts of your computer can sometimes decide to fight over:

    • Interrupts (IRQs): A device requests time from the processor using these interrupt requests. Under traditional designs, each device has a different IRQ number. If two try to use the same one, a conflict can result. Newer technologies can allow multiple devices to share an IRQ channel.

    • Direct Memory Access (DMA) Channels: Some devices have the ability to read and write directly from the system memory, instead of asking the processor to do it for them. Cutting the "middle man" out in this manner improves the efficiency of the system. Each device that does this needs its own DMA channel.

    • Input/Output (I/O) Addresses: Devices exchange information with the system by putting data into certain specific memory addresses. For example, when we pressed the letter "M" in the example mentioned above, the keypress was stored in a certain memory address until it was time for the processor to deal with it. Any time information goes into or out of the machine, to your modem or hard drive or printer for example, it uses these I/O addresses. Again, each device needs its own memory area.

    • Memory Addresses: Similar to I/O addresses, many devices use blocks of memory as part of their normal functioning. For example, they may map hardware programs (BIOS code) into memory, or use a memory area to hold temporary data they are using.



Motherboard and System Devices

The motherboard is, in many ways, the most important component in your computer (not the processor, even though the processor gets much more attention.) As mentioned in the Overview, if the processor is the brain of the computer, then the motherboard and its major components (the chipset, BIOS, cache, etc.) are the major systems that this brain uses to control the rest of the computer. Having a good understanding of how the motherboard and its contained subsystems works is probably the most critical part of getting a good understanding of how PCs work in general.

The motherboard plays an important role in the following important aspects of your computer system (notice how many there are here):

  • Organization: In one-way or another, everything is eventually connected to the motherboard. The way that the motherboard is designed and laid out dictates how the entire computer is going to be organized.

  • Control: The motherboard contains the chipset and BIOS program, which between them control most of the data flow within the computer.

  • Communication: Almost all communication between the PC and its peripherals, other PCs, and you, the user, goes through the motherboard.

  • Processor Support: The motherboard dictates directly your choice of processor for use in the system.

  • Peripheral Support: The motherboard determines, in large part, what types of peripherals you can use in your PC. For example, the type of video card your system will use (ISA, VLB, PCI) is dependent on what system buses your motherboard uses.

  • Performance: The motherboard is a major determining factor in your system's performance, for two main reasons. First and foremost, the motherboard determines what types of processors, memory, system buses, and hard disk interface speed your system can have, and these components dictate directly your system's performance. Second, the quality of the motherboard circuitry and chipset themselves have an impact on performance.

  • Upgradability: The capabilities of your motherboard dictate to what extent you will be able to upgrade your machine. For example, there are some motherboards that will accept regular Pentiums of up to 133 MHz speed only, while others will go to 200 MHz. Obviously, the second one will give you more room to upgrade if you are starting with a 133 MHz Pentium.




The Processor(picture Intel Pentium 4 Willamette 1.8 GHz Socket 423 400 MHz)

One of the smallest parts of the computer but the one that gets most of the attention, the processor is often thought of as the "brain" of the computer. An extremely sophisticated piece of miniaturized electronics, the processor (often called the CPU or Central Processing Unit) is at the bottom of all tasks the PC performs. The processor reads instructions (commands) from memory that tell it what it needs to do to accomplish the work that the user wants, and then executes them.

The processor (really a short form for microprocessor) is the central component of the PC. The processor performs all work that you do on your computer directly or indirectly. The processor plays a significant role in the following important aspects of your computer system:

  • Performance: The processor is probably the most important single determinant of system performance in the PC. While other components also play a key role in determining performance, the processor's capabilities dictate the maximum performance of a system. The other devices only allow the processor to reach its full potential.

  • Software Support: Newer, faster processors enable the use of the latest software. In addition, new processors such as the Pentium with MMX Technology, enable the use of specialized software (shortcuts) not usable on earlier machines.

  • Reliability and Stability: The quality of the processor is one factor that determines how reliably your system will run. While most processors are very dependable, some are not. This also depends to some extent on the age of the processor and how much energy it consumes.

  • Energy Consumption and Cooling: Originally processors consumed relatively little power compared to other system devices. Newer processors can consume a great deal of power. Power consumption has an impact on everything from cooling method selection to overall system reliability.

  • Motherboard Support: The processor you decide to use in your system will be a major determining factor in what sort of chipset you must use, and therefore what motherboard you buy. The motherboard in turn dictates many facets of your system's capabilities and performance.

  • System Memory

The system memory holds all of the "active" information that the computer is using. When you turn the computer on the memory is empty. Each program or data file you load uses part of the system memory. When you close a program the memory is freed up for other uses. Generally, the more memory your system has, the more things you can do with it simultaneously. Increasing the amount of memory in the system also improves performance in most cases.

The system memory is the place where the computer holds current programs and data that are in use. The term "memory" is somewhat ambiguous; it can refer to many different parts of the PC because there are so many different kinds of memory that a PC uses. However, when used by itself, "memory" usually refers to the main system memory or RAM, which holds the instructions that the processor executes and the data that those instructions work with. Your system memory is an important part of the main processing subsystem of the PC, tied in with the processor, cache, motherboard and chipset.

Memory plays a significant role in the following important aspects of your computer system:

  • Performance: The amount and type of system memory you have is an important contributing factor to overall performance. In many ways, it is more important than the processor, because insufficient memory can cause a processor to work at below its performance potential.

  • Software Support: Newer programs require more memory than old ones. More memory will give you access to programs that you cannot use with a lesser amount.

  • Reliability and Stability: Bad memory is a leading cause of mysterious system problems. Ensuring you have high-quality memory will result in a PC that runs smoothly and exhibits fewer problems. Also, even high-quality memory will not work well if you use the wrong kind.

  • Upgradability: There are many different types of memory available, and some are more universal than others. Making a wise choice can allow you to migrate your memory to a future system or continue to use it after you upgrade your motherboard.

Read-Only Memory (ROM)

One major type of memory that is used in PCs is called read-only memory, or ROM for short. ROM is a type of memory that normally can only be read, as opposed to RAM, which can be both read and written. There are two main reasons that read-only memory is used for certain functions within the PC:

  • Performance: The values stored in ROM are always there, whether the power is on or not. A ROM can be removed from the PC, stored for an indefinite period of time, and then replaced, and the data it contains will still be there. For this reason, it is called non-volatile storage. A hard disk is also non-volatile, for the same reason, but regular RAM is not.

  • Security: The fact that ROM cannot easily be modified provides a measure of security against accidental or malicious changes to its contents. You are not going to find viruses infecting true ROMs, it's just not possible. It's technically possible with erasable EPROM's, though in practice never seen.

Read-only memory is most commonly used to store system-level programs that we want to have available to the PC at all times. The most common example is the system BIOS program, which is stored in a ROM called the system BIOS ROM. Having this in a permanent ROM means it is available when the power is turned on so that the PC can use it to boot up the system. Remember that when you first turn on the PC the system memory is empty, so there has to be something for the PC to use when it starts up.

While the whole point of a ROM is supposed to be that the contents cannot be changed, there are times when being able to change the contents of a ROM can be very useful. There are several ROM variants that can be changed under certain circumstances; these can be thought of as "mostly read-only memory". The following are the different types of ROMs with a description of their relative modifiability:

  • ROM: A regular ROM is constructed from hard-wired logic, encoded in the silicon itself, much the way that a processor is. It is designed to perform a specific function and cannot be changed. This is inflexible and so regular ROMs are only used generally for programs that are static and mass-produced. This product is analogous to a commercial software CD-ROM that you purchase in a store.

  • Programmable ROM (PROM): This is a type of ROM that can be programmed using special equipment; it can be written to, but only once. This is useful for companies that make their own ROMs from software they write, because when they change their code they can create new PROMs without requiring expensive equipment. This is similar to the way a CD-ROM recorder works by letting you "burn" programs onto blanks once and then letting you read from them many times. In fact, programming a PROM is also called burning, just like burning a CD-R, and it is comparable in terms of its flexibility.

  • Erasable Programmable ROM (EPROM): An EPROM is a ROM that can be erased and reprogrammed. A little glass window is installed in the top of the ROM package, through which you can actually see the chip that holds the memory. Ultraviolet light of a specific frequency can be shined through this window for a specified period of time, which will erase the EPROM and allow it to be reprogrammed again. Obviously this is much more useful than a regular PROM, but it does require the erasing light. This technology is analogous to a reusable CD-RW.

  • Electrically Erasable Programmable ROM (EEPROM): The next level of erasability is the EEPROM, which can be erased under software control. This is the most flexible type of ROM, and is now commonly used for holding BIOS programs. When you hear reference to a "flash BIOS" or doing a BIOS upgrade by "flashing", this refers to reprogramming the BIOS EEPROM with a special software program. Here we are blurring the line a bit between what "read-only" really means, but remember that this rewriting is done maybe once a year or so, compared to real read-write memory (RAM) where rewriting is done often many times per second.

Note: One thing that sometimes confuses people is that since RAM is the "opposite" of ROM (since RAM is read-write and ROM is read-only), and since RAM stands for "random access memory", they think that ROM is not random access. This is not true; any location can be read from ROM in any order, so it is random access as well, just not write able. RAM gets its name because earlier read-write memories were sequential, and did not allow random access.

Finally, one other characteristic of ROM, compared to RAM, is that it is much slower, typically having double the access time of RAM or more. This is one reason why the code in the BIOS ROM is often shadowed to improve performance.

Random Access Memory (RAM)

The kind of memory used for holding programs and data being executed is called random access memory or RAM. RAM differs from read-only memory (ROM) in that it can be both read and written. It is considered volatile storage because unlike ROM, the contents of RAM are lost when the power is turned off. RAM is also sometimes called read-write memory or RWM. This is actually a much more precise name, so of course it is hardly ever used. ) It's a better name because calling RAM "random access" implies to some people that ROM isn't random access, which is not true. RAM is called "random access" because earlier read-write memories were sequential and did not allow random access. Sometimes, old acronyms persist even when they don't make much sense any more (e.g., the "AT" in the old IBM AT stands for "advanced technology").

Obviously, RAM needs to be write able in order for it to do its job of holding programs and data that you are working on. The volatility of RAM also means that you risk losing what you are working on unless you save it frequently.

RAM is much faster than ROM is, due to the nature of how it stores information. This is why RAM is often used to shadow the BIOS ROM to improve performance when executing BIOS code. There are many different types of RAMs, including static RAM (SRAM) and the many types of dynamic RAM (DRAM).

Static RAM (SRAM)

Static RAM is a type of RAM that holds its data without external refresh, for as long as power is supplied to the circuit. This is contrasted to dynamic RAM (DRAM), which must be refreshed many times per second in order to hold its data contents. SRAMs are used for specific applications within the PC, where their strengths outweigh their weaknesses compared to DRAM:

  • Simplicity: SRAMs don't require external refresh circuitry or other work in order for them to keep their data intact.

  • Speed: SRAM is faster than DRAM.

In contrast, SRAMs have the following weaknesses, compared to DRAMs:

  • Cost: SRAM is, byte for byte, several times more expensive than DRAM.

  • Size: SRAMs take up much more space than DRAMs (which is part of why the cost is higher).

These advantages and disadvantages taken together obviously show that performance-wise, SRAM is superior to DRAM, and we would use it exclusively if only we could do so economically. Unfortunately, 32 MB of SRAM would be prohibitively large and costly, which is why DRAM is used for system memory. SRAMs are used instead for level 1 cache and level 2 cache memory, for which it is perfectly suited; cache memory needs to be very fast, and not very large.

SRAM is manufactured in a way rather similar to how processors are: highly-integrated transistor patterns photo-etched into silicon. Each SRAM bit is comprised of between four and six transistors, which is why SRAM takes up much more space compared to DRAM, which uses only one (plus a capacitor). Because an SRAM chip is comprised of thousands or millions of identical cells, it is much easier to make than a CPU, which is a large die with a non-repetitive structure. This is one reason why RAM chips cost much less than processors do. mb226i3583sbbo

Dynamic RAM (DRAM)

Dynamic RAM is a type of RAM that only holds its data if it is continuously accessed by special logic called a refresh circuit. Many hundreds of times each second, this circuitry reads the contents of each memory cell, whether the memory cell is being used at that time by the computer or not. Due to the way in which the cells are constructed, the reading action itself refreshes the contents of the memory. If this is not done regularly, then the DRAM will lose its contents, even if it continues to have power supplied to it. This refreshing action is why the memory is called dynamic.

All PCs use DRAM for their main system memory, instead of SRAM, even though DRAMs are slower than SRAMs and require the overhead of the refresh circuitry. It may seem weird to want to make the computer's memory out of something that can only hold a value for a fraction of a second. In fact, DRAMs are both more complicated and slower than SRAMs.

The reason that DRAMs are used is simple: they are much cheaper and take up much less space, typically 1/4 the silicon area of SRAMs or less. To build a 64 MB core memory from SRAMs would be very expensive. The overhead of the refresh circuit is tolerated in order to allow the use of large amounts of inexpensive, compact memory. The refresh circuitry itself is almost never a problem; many years of using DRAM has caused the design of these circuits to be all but perfected.

DRAMs are smaller and less expensive than SRAMs because SRAMs are made from four to six transistors (or more) per bit, DRAMs use only one, plus a capacitor. The capacitor, when energized, holds an electrical charge if the bit contains a "1" or no charge if it contains a "0". The transistor is used to read the contents of the capacitor. The problem with capacitors is that they only hold a charge for a short period of time, and then it fades away. These capacitors are tiny, so their charges fade particularly quickly. This is why the refresh circuitry is needed: to read the contents of every cell and refresh them with a fresh "charge" before the contents fade away and are lost. Refreshing is done by reading every "row" in the memory chip one row at a time; the process of reading the contents of each capacitor re-establishes the charge.

DRAM is manufactured using a similar process to how processors are: a silicon substrate is etched with the patterns that make the transistors and capacitors (and support structures) that comprise each bit. DRAM costs much less than a processor because it is a series of simple, repeated structures, so there isn't the complexity of making a single chip with several million individually-located transistors.

There are many different kinds of specific DRAM technologies and speeds that they are available in. These have evolved over many years of using DRAM for system memory.







Video Cards(ATI Radeon 9800 PRO ATI Radeon 9800 Pro 256 MB DDR 256 biti TV-Out -)

Your video card performs the function of displaying the screen you see on the monitor. Inside the video card is a special kind of memory called video memory, where information is stored that represents what you see on the screen. If you look closely at the screen you can see that it is made up of many dots, or pixels. Each pixel's color and brightness is stored in the video memory.

When the computer wants to display something, it calculates how it needs to change the color and brightness of the different pixels, and changes the values in the video memory. The video card then presents the new pixels to you on the monitor. In modern computers, this calculating job is shared between the processor and the video card itself. Having the video card do the calculation can often be much faster, because the video card is specialized to do these types of calculations. Also, while the video card is doing this work, the processor can go on to other things.

Your system's video card is the component responsible for producing the visual output from your computer. Virtually all programs produce visual output; the video card is the piece of hardware that takes that output and tells the monitor which of the dots on the screen to light up (and in what color) to allow you to see it.

Like most parts of the PC, the video card had very humble beginnings, it was only responsible for taking what the processor produced as output and displaying it on the screen. Early on, this was simply text, and not even color at that. Video cards today are much more like coprocessors; they have their own intelligence and do a lot of processing that would otherwise have to be done by the system processor. This is a necessity due to the enormous increase both in how much data we send to our monitors today, and the sophisticated calculations that must be done to determine what we see on the screen. This is particularly so with the rise of graphical operating systems, and 3D computing.

The video card in your system plays a significant role in the following important aspects of your computer system:

  • Performance: The video card is one of the components that has an impact on system performance. For some people (and some applications) the impact is not that significant; for others, the video card's quality and efficiency can impact on performance more than any other component in the PC! For example, many games that depend on a high frame rate (how many times per second the screen is updated with new information) for smooth animation, are impacted far more by the choice of video card than even by the choice of system CPU.

  • Software Support: Certain programs require support from the video card. The software that normally depends on the video card the most includes games and graphics programs. Some programs (for example 3D-enhanced games) will not run at all on a video card that doesn't support them.

  • Reliability and Stability: While not a major contributor to system reliability, choosing the wrong video card can cause problematic system behavior. In particular, some cards or types of cards are notorious for having unstable drivers, which can cause a host of difficulties.

  • Comfort and Ergonomics: The video card, along with the monitor, determine the quality of the image you see when you use your PC. This has an important impact on how comfortable the PC is to use. Poor quality video cards don't allow for sufficiently high refresh rates, causing eyestrain and fatigue.




In simple terms, the monitor, sometimes also called a CRT (Cathode Ray Tube) after the main technology used in making them, is a specialized, high-resolution screen, similar to a high-quality television. Many times per second, your video card sends the contents of its video memory out to your monitor. The screen is made up of a matrix of red, green and blue dots. The information your video card sends controls which dots are lit up and how bright they are, which determines the picture you see.

Your monitor is the component that displays the visual output from your computer as generated by the video card. It is different from most of the other components of the PC due to its passive nature; it isn't responsible for doing any real computing, but rather for showing the results of computing. In this way, the monitor is in many respects more similar to your printer than to anything else in the PC, although of course most people don't think in these terms.

Monitors are important not because of their impact on performance, but rather their impact on the usability of the PC. A poor quality monitor can hamper the use of an otherwise very good PC, because a monitor that is hard to look at can make the PC hard to use. Despite the fact that they don't have a direct impact on performance, many people spend almost as much on their monitor when buying a new PC as they do on the PC system itself.

One reason why this happens is that the monitor is one of the few parts of a PC that actually holds its value. Performance items like CPUs get outdated and lose their value rather quickly, but monitor technology evolves much more slowly. Eventually, monitor costs have come down, but still much more slowly than most other components. This is one big reason why quality is perhaps more important in choosing a monitor than any other part of the system.

Your monitor plays a significant role in the following important aspects of your computer system:

  • Comfort and Ergonomics: Working with your video card, your monitor determines the quality of the image you see when you use your PC. This has an important impact on how comfortable the PC is to use. Poor quality monitors lead directly to eyestrain and other problems, and can ruin the computing experience.

  • Software and Video Mode Support: Use of advanced, high-resolution or high-color-depth video modes requires support for these modes from the monitor. A video card that can drive high resolutions in true color at high refresh rates is useless without a monitor that can handle them as well.

  • Upgradability: Since most monitors are interchangeable with each other and can be used on any similar PC, they are naturals to carry over to a new machine or to use after upgrading. Since they hold their value, a frequent upgrading user with a good monitor can use it for many years and through many changes of processors, memory, motherboards and other components that become dated quite quickly.




Hard Disk Drives(Seagate Barracuda Serial ATA V 80 GB Serial-ATA 7200 rpm 8 MB cache)

Your hard disk drive is your computer's main "long term memory"--it holds your operating system, programs and data files. Hard drives are the fastest form of long-term storage your computer uses. They have currently increased in size and speed to values unheard of just a few years ago. Hard disks are (usually) permanent--they stay in one place inside your computer and cannot be removed the way floppy disks or CD-ROMs can.

The hard disk drive in your system is the "data center" of the PC. It is here that all of your programs and data are stored between the occasions that you use the computer. Your hard disk (or disks) is the most important of the various types of permanent storage used in PCs (the others being floppy disks and other storage media such as CD-ROMs, tapes, removable drives, etc.) The hard disk differs from the others primarily in three ways: size (usually larger), speed (usually faster) and permanence (usually fixed in the PC and not removable).

Hard disk drives are almost as amazing as microprocessors in terms of the technology they use and how much progress they have made in terms of capacity, speed, and price in the last 20 years. The first PC hard disks had a capacity of 10 megabytes and a cost of over $100 per MB. Modern hard disks have capacities approaching 100 gigabytes and a cost of less than 1 cent per MB! This represents an improvement of 1,000,000% in just under 20 years, or around 67% cumulative improvement per year. At the same time, the speed of the hard disk and its interfaces has increased dramatically as well.

Your hard disk plays a significant role in the following important aspects of your computer system:

  • Performance: The hard disk plays a very important role in overall system performance, probably more than most people recognize (though that is changing now as hard drives get more of the attention they deserve). The speed at which the PC boots up and programs load is directly related to hard disk speed. The hard disk's performance is also critical when multitasking is being used or when processing large amounts of data such as graphics work, editing sound and video, or working with databases.

  • Storage Capacity: This is kind of obvious, but a bigger hard disk lets you store more programs and data.

  • Software Support: Newer software needs more space and faster hard disks to load it efficiently. It's easy to remember when 1 GB was a lot of disk space; heck, it's even easy to remember when 100 MB was a lot of disk space! Now a PC with even 1 GB is considered by many to be "crippled", since it can barely hold modern (inflated) operating system files and a complement of standard business software.

  • Reliability: One way to assess the importance of an item of hardware is to consider how much grief is caused if it fails. By this standard, the hard disk is the most important component by a long shot. As I often say, hardware can be replaced, but data cannot. A good quality hard disk, combined with smart maintenance and backup habits, can help ensure that the nightmare of data loss doesn't become part of your life.

This chapter takes a very detailed look at hard disks and how they work. This includes a full dissection of the internal components in the drive, a look at how data is formatted and stored, a discussion of performance issues, and a full analysis of the two main interfaces used to connect hard disks to the rest of the PC. A discussion is also included about the many confusing issues regarding hard disks and BIOS versions, and support for the newer and larger hard disks currently on the market. Finally, a full description is given of logical hard disk structures and the functioning of the FAT and NTFS file systems, by far the most popular currently used by PCs.

Floppy Disk Drives

Floppy disks are your computer's smallest and slowest form of long-term storage. Floppy disks provide a simple, convenient way to transfer information, install new software, and back up small amounts of files. Floppy disks are not as important a part of the computer as they were many years ago. This is largely because the floppy disk still holds the same amount it did five years ago, while most users' needs for storage, software installation and backup, have increased ten-fold or more in that period of time. One great advantage floppy drives have is universality: virtually 100% of PCs made in the last 10 years use a standard 1.44 MB floppy drive.

Sometimes people refer to the hard disk as the "data center" of the PC, and in fact it is, but there was a time when the floppy disk actually held this honor. In fact, the first PCs didn't have hard disks; all of their data storage was done on floppies. There was a time when floppy disk drives were high technology and cost a lot of money. The invention of hard disks relegated floppy disks to the secondary roles of data transfer and software installation. The invention of the CD-ROM and the Internet, combined with the increasingly large size of software files, is threatening even these secondary roles.



The floppy disk still persists, basically unchanged for over a decade, in large part because of its universality; the 3.5 inch 1.44 MB floppy is present on virtually every PC made in the last 10 years, which makes it still a useful tool. The floppy disk's current role is in these areas:

  • Data Transfer: The floppy disk is still the most universal means of transferring files from one PC to another. With the use of compression utilities, even moderate-sized files can be shoehorned onto a floppy disk, and anyone can send anyone a disk and feel quite confident that the PC at the other end will be able to read it. The PC 3.5" floppy is such a standard, in fact, that many Apple and even UNIX machines can read them, making these disks useful for cross-platform transfer.

  • Small File Storage and Backup: The floppy disk is still used for storing and backing up small amounts of data, probably more than you realize.

  • Software Installation and Driver Updates: Many new pieces of hardware still use floppies for distributing driver software and the like, and some software still uses floppies (although this is becoming less common as software grows massive and CD-ROM drives become more universal.)

While floppy drives still have a useful role in the modern PC, there is no denying their reduced importance. Very little attention is paid to floppy "performance" any more, and even choosing makes or models involves a small fraction of the amount of care and attention required for selecting other components. In essence, the floppy drive today is a commodity item.


CD-ROM Drives(Plextor PlexWriter SCSI Intern 40x12x40/)

CD-ROM stands for Compact Disk - Read Only Memory. As the name implies, CD-ROM drives use compact disks, similar to the ones that hold music, to hold computer information. And also as the name implies, they are a read-only medium. You can read information from them but not write to them (except for some special exceptions). CD-ROMs are currently the most popular way that computer companies distribute applications and games, and are ideal for multimedia information like videos, music and large graphics files.

In a few short years, the CD-ROM drive has gone from a pricey luxury to inexpensive necessity on the modern PC. The CD-ROM has opened up new computing vistas that were never possible before, due to its high capacity and broad applicability. In many ways, the CD-ROM has replaced the floppy disk drive, but in many ways it has allowed us to use our computers in ways that we never used them before. In fact, the "multimedia revolution" was largely a result of the availability of cheap CD-ROM drives.

As the name implies, CD-ROMs use compact disks, in fact, the same physical disk format as the ones we use for music. Special formatting is used to allow these disks to hold data. As CD-ROMs have come down in price they have become almost as common in a new PC as the hard disk or floppy disk, and they are now the method of choice for the distribution of software and data due to their combination of high capacity and cheap and easy manufacturing. Recent advances in technology have also improved their performance to levels approaching those of hard disks in many respects.

CD-ROM drives play a significant role in the following essential aspects of your computer system:

  • Software Support: The number one reason why a PC today basically must have a CD-ROM drive is the large number of software titles that are only available on CD-ROM. At one time there were a few titles that came on CD-ROM, and they generally came on floppy disks as well. Today, not having a CD-ROM means losing out on a large segment of the PC software market. Also, some CD-ROMs require a drive that meets certain minimum performance requirements.

  • Performance: Since so much software uses the CD-ROM drive today, the performance level of the drive is important. It usually isn't as important as the performance of the hard drive or system components such as the processor or system memory, but it is still important, depending on what you use the drive for. Obviously, the more you use the CD-ROM, the more essential it is that it perform well.


The keyboard is the main input device for most computers. It is used to input textual information to the PC. Keyboards are pretty much standard affairs these days, although they can vary greatly in quality and appearance, and some have significant additional features.

Keyboards are one of those components that most PC users typically take for granted. This is certainly understandable. For starters, keyboards have no impact on the performance of the PC, which immediately diminishes their importance. They are present on almost every PC ever sold, and usually just "come with" the rest of the hardware. They perform a specific task and for a lot of people, any keyboard will do the job. It’s not like the average PC buyer will select a PC system on the basis of its keyboard! Pretty boring stuff, seemingly.

This can be deceiving, however. Despite the higher profile given to alternative input devices in recent years, the lowly keyboard is still the primary input mechanism for the PC. It is a one-dimensional input device, allowing you to enter text and execute commands on your system. However, even in this day of graphical user interfaces and Internet use, the keyboard has a very important role to play.

The main reason for the keyboard’s importance is that it is one of the most critical ergonomic components in the PC. The design and construction of the keyboard affects the comfort and usability of the PC, especially if you do a lot of typing. (And many people do more typing than they used to--the Internet means more mouse-based graphical browsing, but also email, discussion forums and other text-based activities.) Poor keyboard design and use habits can even lead to health issues in some people: repetitive stress injuries.

Keyboards are probably the most standardized components in the PC, in terms of operation and interface. You can switch most keyboards between PCs and still have them work. This does not, however, mean that all keyboards are the same--far from it. In fact, the interchangeability of most keyboards means you have a wealth of options open to you. This freedom to easily change keyboards means you can readily benefit from understanding the differences between different types.


Until the invention of graphical operating systems, the keyboard was the only way that most people input information into their PCs. Mice are used in graphical environments to let users provide simple "point and click" instructions to the computer. The main advantage of a mouse over the keyboard is simplicity. There are also some operations that are much easier to perform with a mouse than a keyboard (such as picking an item on a screen or choosing from a list of options).

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Mihai Beniuc
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Mircea Eliade Mircea Eliade
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Liviu Rebreanu Liviu Rebreanu
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