64 Bit Computing
The previous generation of processors were 32 bit, meaning that they could address a maximum of 4 gigabytes of memory and could handle whole numbers with values of up to about 2 billion. The new generation of 64 bit computers, by doubling the number of bits, can now theoretically address up to 256 terabytes of memory and can handle whole numbers with values up to about 9,000,000,000,000,000,000. This allows 64 bit systems to process huge amounts of data, for example massive databases or extremely high resolution computer graphics.
Cache memory is a special type of high performance memory used by processors to speed up processing by avoiding access to slower main memory. Cache memory is built into the processor itself and operates at the same speed as the rest of the processor, as opposed to main memory which has to be several times slower.
Having a bigger cache will in most cases result in faster performance. Currently, processor cache sizes up to 8 megabytes are available.
Hard drives are data storage devices built into every computer. You can think of them as being like the computer's filing cabinet, a place where files can be kept for later retrieval. Any program you install on a computer and any file you create will be stored on the hard drive. The drive contains a metal disc with a magnetic coating, spinning at high speed. Data is stored on the disc in a similar manner to how sound and video is recorded onto video tape. Because hard drives are used to store all the data a computer works with they are considered to be a vital part of the system.
The amount of space that a hard drive can use to store files is measured in gigabytes (billions of bytes). One gigabyte (1 GB) is about the same amount of storage as one and a half recordable CDs. A typical music file such as one downloaded from iTunes or Amazon is about 5 megabytes, and there are a thousand megabytes in a gigabyte, so 1 GB is enough for around 200 music files.
As hard drives store everything you work with on your computer, the size of your hard drive is of critical importance - you can never have too much hard drive space. A 20 GB drive, considered a good size only a few years ago, is now thought to be too small to be of much use. Even the cheapest computers currently come with at least an 80 GB drive. For desktops, hard drive size can typically range from 160 GB to 250 GB, though larger sizes are available.
Solid State Drive
Recently a new storage technology has appeared, called Solid State Drives, or SSD for short. Instead of a spinning magnetic disc, these drives use Flash memory chips to store data. Flash memory doesn't lose its contents when it is powered off, making it suitable for storing files. SSDs have several key advantages over mechanical hard drives; they have no moving parts to damage or wear out, making them more likely to survive being dropped. They also use less power, generate less heat and are usually faster than mechanical drives, and are silent in operation. However, they are more expensive than mechanical hard drives, and don't offer as much storage space. The biggest SSDs top out at 128-256 GB, compared to up to 1500 GB for mechanical drives.
Memory is the main working space your computer uses to load running programs and files that you are working on. Computer memory is volatile, meaning that once you turn the computer's power off, you will lose anything that is stored in memory. This is why computers also have hard drives to provide a place for you to keep files when you are not working on them.
The amount of memory a system has is measured in megabytes and gigabytes, like hard drive space. However, due to technical reasons, a gigabyte of computer memory is about 7% more than a gigabyte of hard drive space.
The amount of memory you have will affect how well your computer will run. If a computer doesn't have enough real memory to load a program or open a file it will allocate space on the hard drive to act as "virtual memory" and move parts of memory that aren't being used very often off onto it in order to free space for whatever you want to do. However, if you then decide to switch back to something that was moved to virtual memory, the computer will have to copy it back into main memory from the hard drive. This "paging out" and "paging in" process can slow a computer down noticeably, and the less real memory you have, the more reliant on virtual memory your computer will be and the slower it will run.
Modern computer software is heavily reliant on memory, for example the minimum memory required for Windows Vista is 512 megabytes (half a gigabyte). This won't leave much real memory available though, and your computer will be heavily reliant on virtual memory. You can avoid this problem by installing more memory, at least a gigabyte is recommended for Vista
Traditionally, processors for PCs have been single core, meaning that the processor package contained a chip with a single processing device, known as a core, built into it. As technology has improved, chip manufacturers have found ways of squeezing ever more processing elements onto a single silicon chip. This has led to the idea of multi core processors, where the processor chip contains 2 or more complete processors. With properly written software, a dual core processor can perform nearly twice as much work as a single core processor running at the same speed. Systems with at least 2 processor cores are becoming commonplace.
Almost all computers will support networking in one form or another. This can include wired ethernet, wireless networking or both. Accessing the internet will require networking.
Wireless networking equipment (also often referred to as wi-fi) will support some version of the 802.11 standard, either the mainstream 802.11g or a draft version of the new 802.11n standard (sometimes called n draft). You may also find 802.11a systems, which offer similar performance to 802.11g, but these are rather uncommon. Systems based on 802.11b are generally considered to be obsolete. All versions of 802.11 require you to be within range of a wireless hotspot or router for internet access.
An optical drive is a device that allows you to access or create CDs, DVDs, and/or Blu-Ray discs, depending on the capabilities of the drive. Nearly all drives can read CDs, and most can write ("burn") them. Drives that can read and write DVDs are also common. Most computers come equipped with at least one optical drive, and usually have enough space to install 2 or more.
Newer high-end computers may come with a drive capable of reading Blu-Ray discs, the latest format for high definition movies.
Ports and Connectors
Computers will have at least one video connector of some sort on the back panel to allow them to connect to monitors, projectors, or other display devices. Most machines will have a VGA port (commonly coloured blue) or a more modern DVI port (commonly coloured white). Some machines will have more than one video port, allowing them to drive several displays at once.
Systems with sound will usually have a headphone jack on the front panel for listening in private, and will often also incorporate a microphone jack as well. The back panel will include several jacks for connecting up to surround sound speakers and other audio devices. Some may also include S/PDIF connectors for connecting to high end audio equipment. Some computers will have an internal speaker but this is less common than it used to be.
Most computers will incorporate at least 4 USB ports, as there is a very wide range of accessories that can connect via USB, such as external hard drives, Flash memory sticks, keyboards, mice and many other types of devices. As USB devices are so common, many computers will include more than 4 ports, 6 to 8 ports being common. Most computers include 2 USB ports on the front panel for easy access.
Some computers have an IEEE 1394 port, also known as a FireWire port, or for systems made by Sony an iLink connector. This can be used to connect to external hard drives, several models of video cameras and other computers via their FireWire link.
While PS/2 ports, used for connecting keyboards and mice, are considered to be legacy connectors, they are still very common, as they leave precious USB ports that would otherwise be tied up with a keyboard and mouse free for other devices. These ports are colour coded, purple for keyboards and green for mice.
There are other ports that are also common on the back panels of PCs. An ethernet port, similar in appearance to a telephone jack, is common on machines with Ethernet networking. E-SATA ports are a new type of connector designed for external hard drives. They are still new, but are becoming more common. You might find legacy serial, Centronics or SCSI connectors on the back panel as well, but these are now quite rare as their functions are now provided by newer standards, mostly USB.
The processor is a computer's "brain", responsible for all the operations the computer can perform. The performance of the processor will have a significant impact on the performance of the computer as a whole.
Celeron is the branding Intel uses for a range of lower cost processors for use in value computers.
Core 2 is the branding Intel applies to its current range of processors. The range includes Core 2 Duo for mainstream systems, Core 2 Quad for higher performance computers and Core 2 Extreme for workstations. The Core 2 Duo processors consist of 2 separate processors in a single package and the Quad and Extreme versions include 4 processors.
Core i7 is Intel's latest range of processors, the successor to the current range of Core 2 processors. All the current members of the Core i7 family are quad core, meaning that they effectively contain four separate processors in a single package. Core i7 is expected to offer better performance than the current Core 2 family.
Pentium is the branding Intel uses for a range of lower cost processors for use in value computers. This name had previously been used for Intel's mainstream and high performance processors, but these roles have now been taken by the Core 2 and Core i7 range
AMD's Opteron is a family of processors intended for high end workstations and servers, it is a direct competitor to Intel's Xeon range. They offer features not available on the consumer Semperon and Phenom family, such as support for Fully Buffered memory, multiprocessing support (allowing more than one processor to be installed on the same motherboard) and very large caches. While Opteron is intended for use in the server market, some very high end desktop PCs and workstations use the Opteron as their main processor.
Phenom is AMD's line of processors for mainstream and higher end desktop computers. They are intended to compete with Intel's Core 2 and Core i7 processors. All Phenom process come with at least 3 processing cores (effectively 3 complete processors in a single package), and high end versions have four.
Semperon is the brand name AMD uses for a series of low cost processors intended for use in value products. Semperon processors can be found in many low cost computers and are in direct competition with Intel's Celeron range.
The highest performance server-grade processors from Intel are sold under the Xeon brand. They offer features not available on the consumer Core family, such as support for Fully Buffered memory, multiprocessing support (allowing more than one processor to be installed on the same motherboard) and very large caches. While Xeon is intended for use in the server market, some very high end desktop PCs and workstations use the Xeon as their main processor. For example, the Mac Pro can be purchased with a pair of 4 core Xeon processors, for 8 cores total.
The storage controller is the device that allows the computer to communicate wit hits attached hard drives. IDE and SATA are the common standards for storage controllers.
The video controller is a part of your computer that generates the image that will be displayed on the computer's screen. For desktops you can buy a system that uses integrated graphics built onto the motherboard, or with a more capable dedicated video controller card.
Most discrete video controllers are made by nVidia or ATI/AMD, whereas integrated controllers are typically made by Intel. If you need high performance for tasks like video editing, or want to play games on your computer, then a discrete graphics solution would be a better choice. For general computing tasks such as email, web browsing, word processing, etc, integrated graphics are more than adequate.
Unlike laptops, desktop computers are easily upgradable. If you find that your integrated graphics aren't meeting your needs, you can purchase and install an add-in video controller card with a more powerful graphics processor at a later date. You don't have this option with laptops.
An Integrated Graphics Controller is a video controller that is built into the computer's chipset itself and which uses a portion of the computer's main memory as a frame buffer. Integrated graphics are common on value computers, as they have the advantage of costing less, generating less heat and using less power than discrete video controllers, resulting in quieter running. They can't match the performance of a dedicated solution though, and the portion of the main memory they use as a frame buffer cannot be used for general tasks by the computer, reducing the amount of memory available to the system.
Discrete graphics controller
A discrete graphics controller is an add-in card installed in your computer, whose sole responsibility is managing the display. They also have special dedicated video memory that is separate from the main memory of the rest of the computer. Discrete graphics controllers are more common in gaming computers and workstations, as they offer superior performance compared to integrated graphics and don't take memory away from the rest of the system. The performance comes at a price though, as they are more expensive than integrated controllers and produce more heat, meaning more fan noise.