Computers have enjoyed a lot of different meanings along history. If we do not take into account today?s definition of a computer, similar devices date back to 150-200 BC. Humans were also referred to as computers, when they were performing numerical calculations with the help of a mechanical calculating device.
At the end of the Middle Ages, Wilhelm Schickard constructed one of the first mechanical calculators, and more were on their way. This, however, did not comply with today?s definition of computers. But what standards must the constructed devices meet in order to be classified as a computer?
Computers consist of machines used to manipulate data according to some instructions. This means they have to be programmed before they are put in use. The first step in this direction was made by J.M. Jacquard, by using a series of punch cards as a template in the textile loom. This allowed his loom to weave patterns in accordance to that template, thus obtaining a primordial form of programmability.
The first concept and design of a mechanical computer which could be fully programmable was realized by C. Babbage in 1837. However, because he did not have the necessary finances to build the ?Analytical Engine?, as he named his machine, the project was not continued.
From that point to the 20th century, there were a lot of designs and different machines built that can be classified as computers. The most notable ones were developed in the 30s and 40s and among them we can name Zuse?s ?Z machine?, the British Colossus computer and others.
The 1980s marked a new step in the size and price accessibility of computers. Around the same time the use of a computer in a home became popular. In the 1990s, when the internet was starting to spread considerably, computers were as common as a TV or phone in a regular home.
Today?s computers come in many shapes and sizes. Since the early days, when they occupied the space of a large room, they are now small enough to fit inside a wrist watch. The power of these computers comes from a standard watch battery. Another type of a portable computer finds its form in laptops. A laptop can be considered the equivalent of a personal computer, but with the advantage of portability.
A laptop, also called a notebook, consists of a small computer which weighs between 1 and 6 kilograms or 2 to 12 pounds. Its weight depends on the materials used for fabrication. They usually have a liquid crystals display, a built-in keyboard and a touchpad instead of a mouse, but external accessories such as a keyboard or a mouse can be attached.
The power of a laptop comes from a single main internal battery or an AC/DC adapter, which is usually external. The performances of a laptop are the same as a desktop computer and their components are basically the same, but a laptop is optimized for low power consumption and miniaturized for mobility.
The main disadvantage of laptops is their price. For the same amount you can get a better PC, with higher performances, but you would be tied to your home or office. Even though they cost more, laptops have a lot of advantages to justify the difference.