All computers require either fixed or removable storage for their operating system, programs and user generated material. Formerly the 5 1/4 inch and 3 1/2 inch floppy drive were the principal forms of removable storage for backup of user files and distribution of software. But, as memory sizes increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable media were introduced but never became as prevalant as the floppy drive. By the late 1990′s the optical drive, in CD and later DVD and Blu-ray Disc, became the main method for software distribution, and writeable media provided backup and file interchange. Floppy drives have become uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier. [11]
Early home computers used compact audio cassettes for file storage; these were at the time a very low cost storage solution, but were displaced by floppy disk drives when manfacturing costs dropped, by the mid 1980′s. A second generation of tape recorders was provided when video casssette recorders were pressed into service as backup media for larger disk drives. All these systems were less reliable and slower than purpose-built magnetic tape drives. Such tape drives were uncommon in consumer-type personal computers but were a necessity in business or industrial use.
Interchange of data such as photographs from digital cameras is greatly expedited by installation of a card reader, which often is compatible with several forms of flash memory. It is usually faster and more convenient to move large amounts of data by removing the card from the mobile device, instead of communicating with the mobile device through a USB interface.
A USB flash drive today performs much of the data transfer and backup functions formerly done with floppy drives, Zip disks and other devices. Main-stream current operating systems for personal computers provide standard support for flash drives, allowing interchange even between computers using different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined iwth low cost for high capacity, have made flash drives a popular and useful accessory for any personal computer user.
The operating system (e.g.: Microsoft Windows, Mac OS, Linux or many others) can be located on any removable storage, but typically it is on one of the hard disks. A Live CD is also possible, but it is very slow and is usually used for installation of the OS, demonstrations, or problem solving. Flash-based memory is currently expensive (as of mid-2008) but is starting to appear in laptop computers because of its low weight and low energy consumption, compared to hard disk storage.
These components can usually be put together with little knowledge to build a computer. The motherboard is a main part of a computer that connects all devices together. The memory card(s), graphics card and processor are mounted directly onto the motherboard (the processor in a socket and the memory and graphics cards in expansion slots). The mass storage is connected to it with cables and can be installed in the computer case or in a separate case. This is the same for the keyboard and mouse, except that they are external and connect to the I/O panel on the back of the computer. The monitor is also connected to the I/O panel, either through an onboard port on the motherboard, or a port on the graphics card.
Several functions (implemented by chipsets) can be integrated into the motherboard, typically USB and network, but also graphics and sound. Even if these are present, a separate card can be added if what is available isn’t sufficient. The graphics and sound card can have a break out box to keep the analog parts away from the electromagnetic radiation inside the computer case. For really large amounts of data, a tape drive can be used or (extra) hard disks can be put together in an external case.
The hardware capabilities of personal computers can sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often used for adding expansion cards in personal computers as of 2005 are PCI, AGP (a high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005 have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI Express bus and one or more expansion slots, but few PCs contain both buses.
Netbook PCs are small portable computers in a “clamshell” design, that are designed specifically for wireless communication and access to the Internet. They are generally much lighter and cheaper than subnotebooks, and have a smaller display, between 7″ and 9″, with a screen resolution between 800×600 and 1024×768. The operating systems and applications on them are usually specially modified so they can be comfortably used with a smaller sized screen, and the OS is often based on Linux, although some Netbooks also use Windows XP. Some Netbooks make use of their built in high speed Wireless connectivity to offload some of their applications software to Internet servers, through the principle of Cloud computing, as most Netbooks have small solid state storage systems instead of hard-disks. Storage capacities are usually in the 4 to 12 GB range. One of the first examples of such a system was the original EEE PC.
A pocket PC is a hardware specification for a handheld-sized computer (personal digital assistant) that runs the Microsoft Windows Mobile operating system. It may have the capability to run an alternative operating system like NetBSD or Linux. It has many of the capabilities of modern desktop PCs.
Currently there are thousands of applications for handhelds adhering to the Microsoft Pocket PC specification, many of which are freeware. Some of these devices also include mobile phone features. Microsoft compliant Pocket PCs can also be used with many other add-ons like GPS receivers, barcode readers, RFID readers, and cameras. In 2007, with the release of Windows Mobile 6, Microsoft dropped the name Pocket PC in favor of a new naming scheme. Devices without an integrated phone are called Windows Mobile Classic instead of Pocket PC. Devices with an integrated phone and a touch screen are called Windows Mobile Professional
The capabilities of the PC have changed greatly since the introduction of electronic computers. By the early 1970s, people in academic or research institutions had the opportunity for single-person use of a computer system in interactive mode for extended durations, although these systems would still have been too expensive to be owned by a single person. The introduction of the microprocessor, a single chip with all the circuitry that formerly occupied large cabinets, led to the proliferation of personal computers after about 1975. Early personal computers – generally called microcomputers – were sold often in kit form and in limited volumes, and were of interest mostly to hobbyists and technicians. By the late 1970s, mass-market pre-assembled computers allowed a wider range of people to use computers, focusing more on software applications and less on development of the processor hardware.
Throughout the 1970s and 1980s, home computers were developed for household use, offering personal productivity, programming and games. Somewhat larger and more expensive systems (although still low-cost compared with minicomputers and mainframes) were aimed for office and small business use. Workstations are characterized by high-performance processors and graphics displays, with large local disk storage, networking capability, and running under a multitasking operating system. Workstations are still used for tasks such as computer-aided design, drafting and modelling, computation-intensive scientific and engineering calculations, image processing, architectural modelling, and computer graphics for animation and motion picture visual effects.[1]
Eventually the market segments lost any technical distinction; business computers acquired color graphics capability and sound, and home computers and game systems users used the same processors and operating systems as office workers. Mass-market computers had graphics capabilities and memory comparable to dedicated workstations of a few years before. Even local area networking, originally a way to allow business computers to share expensive mass storage and peripherals, became a standard feature of the personal computers used at home.