Information Technology Last centuries have been characterized by the main technology in those times: XVIII Century: The mechanical systems (Industrial Revolution). XIX Century: The steam machine. XX Century: Information Technology (the recovery, allocation, transformation and distribution of information).

Information Technology Characteristics of the computer industry: Younger than other industries such as the automovile and aereonautics ones. Spectacular development in a short period (half of a century). First two decades: Centralized computacional systems. Computational power:  Universities or medium size enterprices  two computers.  Big enterprices  10 to 12 computers.

Information Technology 20 years later: Same computational power in a processor of the size of a postal stamp. Processors produced by millions. Development of strong ties between computer systems and communications.

Information Technology How the IT became so important? Digital revolution (1959): the chip Microelectronics industry has registered for decades exponencial advances in the cost/capacity relation of processors. Each 18 months the capacity of the chip is doubled. This technological advance has devastated strong and well stablished industries. Eg. The sweeden watch industry, the vinil acoustic disk,..., currently the powerful chemistry based photographic industry.

Personal computers revolution(70s): Apple II Finally appeared a human scale information technology with a friendly face. The personal computer allowed the information technology to reach the small enterprice and the the independent professionals. Final users were liberated from expensive central computer systems and the specialized departments that supported them. Information Technology

Communications revolution (80s): the fiber optics An almost unlimited bandwidth (50,000 Gbps – 50 Tbps) Each year the number of nodes connected to the world wide web douplicates the number. Information Technology

Def. A collection of autonomous and interconnected computer systems is called a computer network. Where: - two computers are interconnected only if they have the possibility of exchanging information. - a system is said to be autonomous if it is not a slave from another system. If a system may start, stop or control another, they are in a Master/Slave relation among them and they are no autonomous. NOTE: A system with a control unit and many terminals is NOT a computer network. Information Technology

Def. A collection of interconnected personal computers (one per user), which share files in one or more computer servers, are said to be in a a client-server architecture. In this model, the users are called clients. Information Technology

Def. A distributed system is a software system built over the network. This software provides the network with a high level grade of cohesion and transparency. Distributed systems vs. Computer networks - In a distributed system the existence of multiple autonomous computers is not visible for the user. - In a computer network the user: - Makes a explicit connection to another machine. - Transfers explicitly from one computer to another. - Controls the network explicitly. - In a distributed system this manipulation is realized by the system without user notification. Information Technology

Transmission media Guided transmission Cooper wire Twisted Pair – Telephone system  Two insulated cooper wires, typically about 1 mm thick.  The wires are twisted together in a helical form (just like the DNA molecule).  Two parallel wires constitute a simple antenna; a twisted pair does not!! Coaxial Cable – TV Cable  Consists of a stiff copper wire as the core, surrounded by an insulating material. The insulator is encased by a cylindrical conductor, which is covered in a protective plastic sheath.  It can span longer distances than the twisted pair and at higher speeds.  In Netherlands, 90% of all homes have a TV cable connection.  In the United States, a TV cable connection runs past the 80% of all homes. Information Technology

Guided transmission (cont.) Fiber Optics An optical transmission system has three components: the light source, the transmission media and the detector. The transmission medium is an ultra-thin fiber of glass. The faster transmission medium known today. An almost unlimited bandwidth (50,000 Gbps – 50 Tbps) Information Technology

Unguided transmission Wireless communication (Mobil users) Broadcasting  Amplitude Modulation – AM  Frequency Modulation – FM Microwaves  Above 100 MHz, waves travel in straight lines.  Relatively inexpensive.  Geosynchronous Communication Satellites are needed to transmit microwaves to other parts of the world. Infrared communication  Widely used for short-range communication.  Remote controls used on television, VCRs and stereos all use infrared communication.  They do not pass through solid objects. Information Technology