Hardware Information
A computer is a machine that manipulates data according to a list of instructions.
The first devices that resemble modern computers date to the mid-20th century (1940–1945), although the computer concept and various machines similar to computers existed earlier. Early electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers (PC).
Modern computers are based on tiny integrated circuits and are millions to billions of times more capable while occupying a fraction of the space. Today, simple computers may be made small enough to fit into a wristwatch and be powered from a watch battery.
The ability to store and execute lists of instructions called programs makes computers extremely versatile and distinguishes them from calculators. The Church–Turing thesis is a mathematical statement of this versatility: any computer with a certain minimum capability is, in principle, capable of performing the same tasks that any other computer can perform. Therefore, computers with capability and complexity ranging from that of a personal digital assistant to a supercomputer are all able to perform the same computational tasks given enough time and storage capacity.
Desktop Computers
A desktop computer is a personal computer (PC) in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Prior to the wide spread of microprocessors a computer that could fit on a desk was considered remarkably small. Today the phrase usually indicates a particular style of computer case. Desktop computers come in a variety of styles ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD monitor. In this sense, the term 'desktop' refers specifically to a horizontally-oriented case, usually intended to have the display screen placed on top to save space on the desk top. Most modern desktop computers have separate screens and keyboards.
Laptop Computers
A laptop (also known as a notebook) is a personal computer designed for mobile use small enough to sit on one's lap. A laptop includes most of the typical components of a typical desktop computer, including a display, a keyboard, a pointing device (a touchpad, also known as a trackpad, or a pointing stick) as well as a battery, into a single small and light unit. The rechargeable battery required is charged from an AC/DC adapter and typically stores enough energy to run the laptop for several hours.
Laptops are usually shaped like a large notebook. Modern laptops weigh 3 to 12 pounds (1.4 to 5.4 kg); older laptops were usually heavier. Most laptops are designed in the flip form factor to protect the screen and the keyboard when closed. Modern 'tablet' laptops have a complex joint between the keyboard housing and the display, permitting the display panel to twist and then lay flat on the keyboard housing. They usually have a touchscreen display and some include handwriting recognition or graphics drawing capability.
Laptops were originally considered to be "a small niche market" and were thought suitable mostly for "specialized field applications" such as "the military, the Internal Revenue Service, accountants and sales representatives". Battery-powered portable computers had just 2% worldwide market share in 1986. But today, there are already more laptops than desktops in businesses, and laptops are becoming obligatory for student use and more popular for general use. According to a forecast by Intel, more laptops than desktops will be sold in the general PC market as soon as 2009.