Software refers to parts of the computer which do not have a material form, such as programs, data, protocols, etc. When software is stored in hardware that cannot easily be modified (such as BIOS ROM in an IBM PC compatible), it is sometimes called "firmware" to indicate that it falls into an uncertain area somewhere between hardware and software.
The term hardware covers all of those parts of a computer that are tangible objects. Circuits, displays, power supplies, cables, keyboards, printers and mice are all hardware.
| Peripheral device (Input/output) | Input | Mouse, Keyboard, Joystick, Image scanner |
| Output | Monitor, Printer | |
| Both | Floppy disk drive, Hard disk, Optical disc drive, Teleprinter | |
| Computer busses | Short range | RS-232, SCSI, PCI, USB |
| Long range (Computer networking) | Ethernet, ATM, FDDI |
A computer's memory can be viewed as a list of cells into which numbers can be placed or read. Each cell has a numbered "address" and can store a single number. The computer can be instructed to "put the number 123 into the cell numbered 1357" or to "add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595". The information stored in memory may represent practically anything. Letters, numbers, even computer instructions can be placed into memory with equal ease. Since the CPU does not differentiate between different types of information, it is up to the software to give significance to what the memory sees as nothing but a series of numbers.
In almost all modern computers, each memory cell is set up to store binary numbers in groups of eight bits (called a byte). Each byte is able to represent 256 different numbers; either from 0 to 255 or -128 to +127. To store larger numbers, several consecutive bytes may be used (typically, two, four or eight). When negative numbers are required, they are usually stored in two's complement notation. Other arrangements are possible, but are usually not seen outside of specialized applications or historical contexts. A computer can store any kind of information in memory as long as it can be somehow represented in numerical form. Modern computers have billions or even trillions of bytes of memory.
The CPU contains a special set of memory cells called registers that can be read and written to much more rapidly than the main memory area. There are typically between two and one hundred registers depending on the type of CPU. Registers are used for the most frequently needed data items to avoid having to access main memory every time data is needed. Since data is constantly being worked on, reducing the need to access main memory (which is often slow compared to the ALU and control units) greatly increases the computer's speed.
Computer main memory comes in two principal varieties: random access memory or RAM and read-only memory or ROM. RAM can be read and written to anytime the CPU commands it, but ROM is pre-loaded with data and software that never changes, so the CPU can only read from it. ROM is typically used to store the computer's initial start-up instructions. In general, the contents of RAM is erased when the power to the computer is turned off while ROM retains its data indefinitely. In a PC, the ROM contains a specialized program called the BIOS that orchestrates loading the computer's operating system from the hard disk drive into RAM whenever the computer is turned on or reset. In embedded computers, which frequently do not have disk drives, all of the software required to perform the task may be stored in ROM. Software that is stored in ROM is often called firmware because it is notionally more like hardware than software. Flash memory blurs the distinction between ROM and RAM by retaining data when turned off but being rewritable like RAM. However, flash memory is typically much slower than conventional ROM and RAM so its use is restricted to applications where high speeds are not required.
In more sophisticated computers there may be one or more RAM cache memories which are slower than registers but faster than main memory. Generally computers with this sort of cache are designed to move frequently needed data into the cache automatically, often without the need for any intervention on the programmer's part.
Windows XP is a line of operating systems developed by Microsoft for use on general-purpose computer systems, including home and business desktops, notebook computers, and media centers. The letters "XP" is an abbreviation for eXPerience.[2] It was codenamed "Whistler", after Whistler, British Columbia, as many Microsoft employees skied at the Whistler-Blackcomb ski resort during its development. Windows XP is the successor to both Windows 2000 Professional and Windows Me, and is the first consumer-oriented operating system produced by Microsoft to be built on the Windows NT kernel and architecture. Windows XP was first released on October 25, 2001, and over 400 million copies were in use in January 2006, according to an estimate in that month by an IDC analyst.[3] It is succeeded by Windows Vista, which was released to volume license customers on November 8, 2006, and worldwide to the general public on January 30, 2007.
The most common editions of the operating system are Windows XP Home Edition, which is targeted at home users, and Windows XP Professional, which has additional features such as support for Windows Server domains and two physical processors, and is targeted at power users and business clients. Windows XP Media Center Edition has additional multimedia features enhancing the ability to record and watch TV shows, view DVD movies, and listen to music. Windows XP Tablet PC Edition is designed to run the ink-aware Tablet PC platform. Two separate 64-bit versions of Windows XP were also released, Windows XP 64-bit Edition for IA-64 (Itanium) processors and Windows XP Professional x64 Edition for x86-64.
Windows XP is known for its improved stability and efficiency over the 9x versions of Microsoft Windows. It presents a significantly redesigned graphical user interface, a change Microsoft promoted as more user-friendly than previous versions of Windows. New software management capabilities were introduced to avoid the "DLL hell" that plagued older consumer-oriented 9x versions of Windows. It is also the first version of Windows to use product activation to combat software piracy, a restriction that did not sit well with some users and privacy advocates. Windows XP has also been criticized by some users for security vulnerabilities, tight integration of applications such as Internet Explorer and Windows Media Player, and for aspects of its default user interface.
Windows XP had been in development since early 1999, when Microsoft started working on Windows Neptune, an operating system intended to be the "Home Edition" equivalent to Windows 2000 Professional. It was eventually merged into the Whistler project, which later became Windows XP.
An operating system (OS) is the software that manages the sharing of the resources of a computer and provides programmers with an interface used to access those resources. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. At the foundation of all system software, an operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking and managing file systems. Most operating systems come with an application that provides a user interface for managing the operating system, such as a command line interpreter or graphical user interface. The operating system forms a platform for other system software and for application software.
The most commonly-used contemporary desktop and laptop (notebook) OS is Microsoft Windows. More powerful servers often employ Linux, FreeBSD, and other Unix-like systems. However, these operating systems, especially Mac OS X, are also used on personal computersComputer security is a branch of information security applied to both theoretical and actual computer systems. Computer security is a branch of computer science that addresses enforcement of 'secure' behavior on the operation of computers. The definition of 'secure' varies by application, and is typically defined implicitly or explicitly by a security policy that addresses confidentiality, integrity and availability of electronic information that is processed by or stored on computer systems.
The traditional approach is to create a trusted security kernel that exploits special-purpose hardware mechanisms in the microprocessor to constrain the operating system and the application programs to conform to the security policy. These systems can isolate processes and data to specifier domains and restrict access and privileges of users. This approach avoids trusting most of the operating system and applications.
In addition to restricting actions to a secure subset, a secure system should still permit authorized users to carry out legitimate and useful tasks. It might be possible to secure a computer against misuse using extreme measures:
| “ | The only truly secure system is one that is powered off, cast in a block of concrete and sealed in a lead-lined room with armed guards - and even then I have my doubts. | ” |
It is important to distinguish the techniques used to increase a system's security from the issue of that system's security status. In particular, systems which contain fundamental flaws[1] in their security designs cannot be made secure without compromising their usability.[citation needed] Most computer systems cannot be made secure even after the application of extensive "computer security" measures. Furthermore, if they are made secure, functionality and ease of use often decreases.
Computer security can also be seen as a subfield of security engineering, which looks at broader security issues in addition to computer security.
Unlike most touchscreens, Surface can respond to more than one touch at a time. During a demonstration with a reporter last week, Mark Bolger, the Surface Computing group's marketing director, "dipped" his finger in an on-screen paint palette, then dragged it across the screen to draw a smiley face. Then he used all 10 fingers at once to give the face a full head of hair.
With a price tag between $5,000 and $10,000 per unit, Microsoft isn't immediately aiming for the finger painting set. (The company said it expects prices to drop enough to make consumer versions feasible in three to five years.)
Some of the first Surface models are planned to help customers pick out new cell phones at T-Mobile stores. When customers plop a phone down on the screen, Surface will read its bar code and display information about the handset. Customers can also select calling plans and ringtones by dragging icons toward the phone.
Guests sitting in some Starwood Hotel lobbies will be able to cluster around the Surface to play music, then buy songs using a credit card or rewards card tagged with a bar code. In some hotel restaurants, customers will be able to order food and drinks, then split the bill by setting down a card or a room key and dragging their menu items "onto" the card.
At Harrah's locations, visitors will be able to learn about nearby Harrah's venues on an interactive map, then book show tickets or make dinner reservations.
Microsoft is working on a limited number of programs to ship with Surface, including one for sharing digital photographs.
Bolger placed a card with a bar code onto Surface's surface; digital photographs appeared to spill out of the card into piles on the screen. Several people gathered around the table pulled photos across the screen using their fingertips, rotated them in circles and even dragged out the corners to enlarge the images — behavior made possible by the advanced graphics support deep inside Windows Vista.
"It's not a touch screen, it's a grab screen," Bolger said.
Historically, Microsoft has focused on creating new software, giving computer programmers tools to build applications on its platforms, and left hardware manufacturing to others. (Some recent exceptions include the Xbox 360 and the Zune music player, made by the same Microsoft division that developed Surface.)
For now, Microsoft is making the Surface hardware itself, and has only given six outside software development firms the tools they need to make Surface applications.
Matt Rosoff, an analyst at the independent research group Directions on Microsoft, said in an interview that keeping the technology's inner workings under wraps will limit what early customers — the businesses Microsoft is targeting first with the machine — will be able to do with it.
But overall, analysts who cover the PC industry were wowed by Surface.
Surface is "important for Microsoft as a promising new business, as well as demonstrating very concretely to the market that Microsoft still knows how to innovate, and innovate in a big way," said Michael Gartenberg, an analyst at Jupiter Research.
The term wireless is normally used to refer to any type of electrical or electronic operation which is accomplished without the use of a "hard wired" connection. Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires".[1] The distances involved may be short (a few meters as in television remote control) or very long (thousands or even millions of kilometers for radio communications). When the context is clear the term is often simply shortened to "wireless". Wireless communications is generally considered to be a branch of telecommunications.
It encompasses cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice and keyboards, satellite television and cordless telephones.
A desktop computer is an electronic machine computer which convert raw data into meaningful information, made for use on a desk in an office or home and is distinguished from portable computers such as laptops or PDAs. Desktop computers are also known as microcomputers. There are four types of desktop computers: home computers, or personal computers; workstations, Internet servers, and special communications computers.
Desktops are currently the most affordable computers and ubiquitous in businesses, schools, and households; they are used for performing office tasks, organizing digital photos, video editing, and Internet access. Nearly all desktop computers are modular, with components that can easily be replaced or upgraded.
Desktop computers come in a variety of case styles ranging from large vertical towers to small form factor models that can be tucked behind an LCD monitor.
Desktop computers are commonly connected to a power strip.
Because of their small size, most palmtop computers do not include disk drives. However, many contain PCMCIA slots in which you can insert disk drives, modems, memory, and other devices.
Palmtops are also called PDAs, hand-held computers and pocket computers.
A laptop computer, or simply laptop (also notebook computer or notepad), is a small mobile computer, which usually weighs 2-18 pounds (around 1 to 8 kilograms), depending on size, materials, and other factors.
Laptops usually run on a single main battery or from an external AC/DC adapter which can charge the battery while also supplying power to the computer itself. Many computers also have a 3 volt cell to run the clock and other processes in the event of a power failure.
As Personal computers, laptops are capable of the same tasks as a desktop computer, although they are typically less powerful for the same price. They contain components that are similar to their desktop counterparts and perform the same functions, but are miniaturized and optimized for mobile use and efficient power consumption. Laptops usually have liquid crystal displays and most of them use different memory modules for their random access memory (RAM), for instance, SO-DIMM in lieu of the larger DIMMs. In addition to a built-in keyboard, they may utilize a touchpad (also known as a trackpad) or a pointing stick for input, though an external keyboard or mouse can usually be attached.
