Features

Many different features are available on today's computer, but only the standard, essential features will be discussed here. These features are grouped into subheadings below for ease of use.
Memory: Each computer has a processor speed of 166 MHz. The Compaq has the least amount of standard memory with 16 MB, with a maximum of 48 MB. Both the Dell and Gateway computers come with 40 MB installed with their maximums being 72 and 80 MB respectively. The Micron had the most standard memory at 48 MB, having a maximum at 80 MB also. The Micron machine rates best in this area.Weight: For laptop computers, travel weight, that is the weight of all of the required equipment and carrying case, is very important. The Compaq and Dell come in with the lowest travel weight at 8.5 pounds. The Gateway came in right behind them with 8.6 pounds travelling. Of the four computers, the Micron was the heaviest, weighting in at 9.1 pounds. The Dell and Compaq are the best in the weight department.Battery: Another key factor for laptop computers is the length of time they can operate away from an outlet. The Dell computer had the longest rated battery life with a rating of 4 to 5 hours. Compaq's computer had a rating of 3 hours while Gateway and Micron's laptops were rated with 2.5 and 2.25 hours, respectively. Dell's computer has the best rating for battery life .Storage: All computers rely on their storage unit to operate for the use of programs and storing information. The Presario had the smallest standard hard drive at 1.4 GB. Both the Dell and the Gateway computers had 2.1 GB hard drives. Micron rates at the top for this category for its 3 GB hard drive .
Overall, the Latitude from Dell gets the best rating for this section. It's light weight and long battery life aid in portability, and while its hard drive and memory are average for this group, they are more than sufficient for good performance.

Economecs and health

Because of their small and flat keyboard and trackpad pointing devices, prolonged use of laptops can cause repetitive strain injury. Usage of separate, external ergonomic keyboards and pointing devices is recommended to prevent injury when working for long periods of time; they can be connected to a laptop easily by USB or via a docking station. Some health standards require ergonomic keyboards at workplaces.
The integrated screen often causes users to hunch over for a better view, which can cause neck or spinal injuries. A larger and higher-quality external screen can be connected to almost any laptop to alleviate that and to provide additional "screen estate" for more productive work.
A study by State University of New York researchers found that heat generated from laptops can raise the temperature of the scrotum when balancing the computer on one's lap, potentially putting sperm count at risk. The small study, which included little more than two dozen men aged 21 to 35, found that the sitting position required to balance a laptop can raise scrotum temperature by as much as 2.1 °C (3.8 °F). Heat from the laptop itself can raise the temperature by another 0.7 °C (1.4 °F), bringing the potential total increase to 2.8 °C (5.2 °F). However, further research is needed to determine whether this directly affects sterility in men.
A common practical solution to this problem is to place the laptop on a table or desk. Another solution is to obtain a cooling unit for the laptop, these units are usually USB powered consist of a hard thin plastic case housing 1, 2 or 3 cooling fans (the whole thing is designed to sit under a laptop) which results in the laptop remaining cool to the touch, and greatly reduces laptop heat generation. There are several companies which make these coolers.
Heat from using a laptop on the lap can also cause skin discoloration on the thighs.

Advantages of laptops

Portability is usually the first feature mentioned in any comparison of laptops versus desktop PCs[40]. Portability means that a laptop can be used in many places—not only at home and at the office, but also during commuting and flights, in coffee shops, in lecture halls and libraries, at clients' location or at a meeting room, etc. The portability feature offers several distinct advantages:
Getting more done – Using a laptop in places where a desktop PC can't be used, and at times that would otherwise be wasted. For example, an office worker managing his e-mails during an hour-long commute by train, or a student doing her homework at the university coffee shop during a break between lectures.Immediacy – Carrying a laptop means having instant access to various information, personal and work files. Immediacy allows better collaboration between coworkers or students, as a laptop can be flipped open to present a problem or a solution anytime, anywhere.
Up-to-date information – If a person has more than one desktop PC, a problem of synchronization arises: changes made on one computer are not automatically propagated to the others. There are ways to resolve this problem, including physical transfer of updated files (using a USB stick or CDs) or using synchronization software over the Internet. However, using a single laptop at both locations avoids the problem entirely, as the files exist in a single location and are always up-to-date.
Connectivity – A proliferation of Wi-Fi wireless networks and cellular broadband data services (HSDPA, EVDO and others) combined with a near-ubiquitous support by laptops, means that a laptop can have easy Internet and local network connectivity while remaining mobile. Wi-Fi networks and laptop programs are especially widespread at university campuses.Other advantages of laptops include:
Size – Laptops are smaller than standard PCs. This is beneficial when space is at a premium, for example in small apartments and student dorms. When not in use, a laptop can be closed and put away.
Low power consumption – Laptops are several times more power-efficient than desktops. A typical laptop uses 20-90 W, compared to 100-800 W for desktops. This could be particularly beneficial for businesses (which run hundreds of personal computers, multiplying the potential savings) and homes where there is a computer running 24/7 (such as a home media server, print server, etc.)
Quiet – Laptops are often quieter than desktops, due both to the components (quieter, slower 2.5-inch hard drives) and to less heat production leading to use of fewer and slower cooling fans.
Battery – a charged laptop can run several hours in case of a power outage and is not affected by short power interruptions and brownouts. A desktop PC needs a UPS to handle short interruptions, brownouts and spikes; achieving on-battery time of more than 20–30 minutes for a desktop PC requires a large and expensive UPS

components of laptop

The basic components of laptops are similar in function to their desktop counterparts, but are miniaturized, adapted to mobile use, and designed for low power consumption. Because of the additional requirements, laptop components usually are of inferior performance compared to similarly priced desktop parts. Furthermore, the design bounds on power, size, and cooling of laptops limit the maximum performance of laptop parts compared to that of desktop components. [29]
The following list summarizes the differences and distinguishing features of laptop components in comparison to desktop personal computer parts:
Motherboard – laptop motherboards are highly make and model specific, and do not conform to a desktop form factor. Unlike a desktop board that usually has several slots for expansion cards (3 to 7 are common), a board for a small, highly integrated laptop may have no expansion slots at all, with all the functionality implemented on the motherboard itself; the only expansion possible in this case is via an external port such as USB or a card slot such as PCMCIA. Other boards may have one or more standard, such as ExpressCard, or proprietary expansion slots. Several other functions (storage controllers, networking, sound card and external ports) are implemented on the motherboard.[30]
Central processing unit (CPU) – Laptop CPUs have advanced power-saving features and produce less heat than desktop processors, but are not as powerful.[31] There is a wide range of CPUs designed for laptops available from Intel (Pentium M, Celeron M, Intel Core and Core 2 Duo), AMD (Athlon, Turion 64, and Sempron), VIA Technologies, Transmeta and others. On the non-x86 architectures, Motorola and IBM produced the chips for the former PowerPC-based Apple laptops (iBook and PowerBook). Some laptops have removable CPUs, although support by the motherboard may be restricted to the specific models.[32] In other laptops the CPU is soldered on the motherboard and is non-replaceable.

A SODIMM memory module.
Memory (RAM) – SO-DIMM memory modules that are usually found in laptops are about half the size of desktop DIMMs.[30] They may be accessible from the bottom of the laptop for ease of upgrading, or placed in locations not intended for user replacement such as between the keyboard and the motherboard. Currently, most midrange laptops are factory equipped with 3-4 GB of DDR2 RAM, while some higher end notebooks feature up to 8 GB of DDR3 memory. Netbooks however, are commonly equipped with only 1 GB of RAM to keep manufacturing costs low.
Expansion cards – A PC Card (formerly PCMCIA) or ExpressCard bay for expansion cards is often present on laptops to allow adding and removing functionality, even when the laptop is powered on. Some subsystems (such as Wi-Fi or a cellular modem) can be implemented as replaceable internal expansion cards, usually accessible under an access cover on the bottom of the laptop. Two popular standards for such cards are MiniPCI and its successor, the PCI Express Mini. [33]
Power supply – Laptops are typically powered by an internal rechargeable battery that is charged using an external power supply. The power supply can charge the battery and power the laptop simultaneously; when the battery is fully charged, the laptop continues to run on AC power. The charger adds about 400 grams (1 lb) to the overall "transport weight" of the notebook.
Battery – Current laptops utilize lithium ion batteries, with more recent models using the new lithium polymer technology. These two technologies have largely replaced the older nickel metal-hydride batteries. Typical battery life for standard laptops is two to five hours of light-duty use, but may drop to as little as one hour when doing power-intensive tasks. A battery's performance gradually decreases with time, leading to an eventual replacement in one to three years, depending on the charging and discharging pattern. This large-capacity main battery should not be confused with the much smaller battery nearly all computers use to run the real-time clock and to store the BIOS configuration in the CMOS memory when the computer is off. Lithium-ion batteries do not have a memory effect as older batteries may have. The memory effect happens when one does not use a battery to its fullest extent, then recharges the battery. New innovations in laptops and batteries have seen new possible matchings which can provide up to a full 24 hours of continued operation, assuming average power consumption levels. An example of this is the HP EliteBook 6930p when used with its ultra-capacity battery.
Video display controller – On standard laptops the video controller is usually integrated into the chipset. This tends to limit the use of laptops for gaming and entertainment, two fields which have constantly escalating hardware demands[34]. Higher-end laptops and desktop replacements in particular often come with dedicated graphics processors on the motherboard or as an internal expansion card. These mobile graphics processors are comparable in performance to mainstream desktop graphic accelerator boards.[35]
Display – Most modern laptops feature 12 inch (30 cm) or larger color active matrix displays with resolutions of 1024×768 pixels and above. Many current models use screens with higher resolution than typical for desktop PCs (for example, the 1440×900 resolution of a 15" Macbook Pro[36] can be found on 19" widescreen desktop monitors).

A size comparison of 3.5" and 2.5" hard disk drives
Removable media drives – A DVD/CD reader/writer drive is typically standard. CD drives are becoming rare, while Blu-Ray is becoming more common on notebooks[37]. Many ultraportables and netbooks either move the removable media drive into the docking station or exclude it altogether.
Internal storage – Laptop Hard disks are physically smaller—2.5 inch (60 mm) or 1.8 inch (46 mm) —compared to desktop 3.5 inch (90 mm) drives. Some newer laptops (usually ultraportables) employ more expensive, but faster, lighter and power-efficient Flash memory-based SSDs instead. Currently, 250 to 320 GB sizes are common for laptop hard disks (64 to 128 GB for SSDs).
Input – A pointing stick, touchpad or both are used to control the position of the cursor on the screen, and an integrated keyboard is used for typing. External keyboard and mouse may be connected using USB or PS/2 (if present).
Ports – several USB ports, an external monitor port (VGA or DVI), audio in/out, and an Ethernet network port are found on most laptops. Less common are legacy ports such as a PS/2 keyboard/mouse port, serial port or a parallel port. S-video or composite video ports are more common on consumer-oriented notebooks.

Laptop

A laptop computer or simply laptop, also called a notebook computer or sometimes a notebook, is a small personal computer designed for mobility. Usually all of the interface hardware needed to operate the laptop, such as parallel and serial ports, graphics card, sound channel, etc., are built in to a single unit. Most laptops contain batteries to facilitate operation without a readily available electrical outlet. In the interest of saving power, weight and space, they usually share RAM with the video channel, slowing their performance compared to an equivalent desktop machine.
One main drawback of the laptop is that, due to the size and configuration of components, relatively little can be done to upgrade the overall computer from its original design. Some devices can be attached externally through ports (including via USB), however internal upgrades are not recommended or in some cases impossible, making the desktop PC more modular.
A subtype of notebooks, called subnotebooks, are computers with most of the features of a standard laptop computer but smaller. They are larger than hand-held computers, and usually run full versions of desktop/laptop operating systems. Ultra-Mobile PCs (UMPC) are usually considered subnotebooks, or more specifically, subnotebook Tablet PCs (see below). Netbooks are sometimes considered in this category, though they are sometimes separated in a category of their own (see below).
Desktop replacements, meanwhile, are large laptops meant to replace a desktop computer while keeping the mobility of a laptop.

[edit] Netbook