Hardware: consists of all the physical components of the computer (what we can see and touch). Example: a keyboard, a microprocessor, a screen…Main components  Motherboard: is a rigid plastic sheet with an engraved circuit on the surface where all the rest of the components are connected to.  Microprocessor: is an integrated circuit that acts as the computer´s brain. The chips have thousands of miniature electronic components.  RAM memory: a computer´s microprocessor continuously works with a large volume of information. In order to process this information and obtain useful results, it must temporarily store data and programs.  Ports: are electrical connections that make it possible for the microprocessor to communicate with the peripherals Operating system components is composed of a set of software packages that can be used for managing the interactions with the hardware.  kernel or core, represents the basic operations of the Operating System.  command line or shell prompt, enables the communication with the Operating System through a control language  File System, that allows the registration of files in a tree structure.

The Operating System: user-aplication-operating system-hardware.several functions: Processor management: the Operating System distributes the processor between the different programs through a scheduling algorithm. Random Access Memory management: the Operating System is responsible for handling, where relevant, the memory space assigned for each application and for each user. When the physical memory is insufficient, the Operating System can create a memory area “virtual memory”.  Input/Output management: the Operating System enables the unification and supervise the access of the programs to the material resources through the drivers.  Execution of applications management: the Operating System is responsible for ensuring that the applications are run without problems  Authorisation management: the Operating System coordinates the security in relation to the execution of programs to ensure that the resources are used by only programs and users with the corresponding authorizations. –File management: the Operating System manages the reading and writing in the File System. Information management: the Operating System provides a certain amount of indicators that may be used for diagnosing the proper operation of the equipment. 

Parts hard disk  Platter: each of the disks that there are inside the hard disk.  Side: each of both sides of a platter.  Head: number of heads.  Tracks: a circumference inside a side; the track 0 is located at the outer edge.  Cylinder: set of several tracks; it represents all the circumferences that are vertically aligned (one of each side).  Sector: each of the divisions of a track. Characteristics of a hard disk:  Interface: medium of communication between the hard disk and the computer.  Average access time: average time taken by the needle while positioning in the desired track and sector.  Average seek time: average time taken by the needle while positioning in the desired track  Read/Write time: average time taken by the disk while reading or writing new information  Average latency: average time taken by the needle while positioning in the desired sector  Rotation speed: platter´s revolutions per minute. The more rotation speed, the less average latency.  Transfer rate: velocity to which can be transmitted information to the computer when the needle is positioned in the right sector and track  Cache memory: is a Flash type memory inside the hard disk.  Landz: zone where the heads are parked when the computer is switched off. 

File extension: compressed .7z, .rar, .zip Audio .mp3, .wav, .wmaExecutable .exe Videoavi, .mpg, .wmv, .divxImages .jpg, .gif, .png, .bmp, .tifPlain text .txt Document .pdf Text document .doc, .docx, .odtPresentation .ppt, .pps, .pptx, .odpSpreadsheet .xls, .xlsx, .odsDatabase .accdb, .mdb, .odbWeb .htm, .html, .php, .swfTypes of networks its size or coverage area:  Personal Area Networks (PAN): communicates devices in the range of few meters Local Area Networks (LAN): small area, like in a house  Metropolitan Area Networks (MAN): for a city.  Wide Area Networks (WAN): connect devices among different cities, countries or continents. The basics of networks  Communication: is the process that carries a message from a sender through a channel to a receiver.  Protocol: is the language and set of rules for which sender and receiver communicate.  Private IP Address: identifies each device in the network.  Public IP Address: is that IP address visible from Internet. Gateway: is the IP address through which the local network sets off towards the exterior, either other network or Internet.  Network mask: similar to the IP address.It is used for creating subnetworks.  DNS: IP addresses are hard to remember. MAC Address: the unique identifier of a device in a network. It consists of 6 hexadecimal pairs of numbers Port: interface to communicate with a program through a network. For instance, the http service uses the port 80 and the ftp service uses the port 21.

Frequency and wavelength The frequency (f) of a wave is the number of oscillations per second. The frequency is measured in Hertz (Hz) and its multiples, Kilohertz (KHz), Megahertz (MHz) and Gigahertz (GHz).  The wavelength (λ) is the distance between two points of the wave in the same state of oscillation. The wavelength (λ) and the frequency (f) are related through the formula: c=λ*f where “c” is the speed of light. Clearing the wavelength it remains: λ = ????????Cryptography The encryption of messages is without question one of the most ancient systems to protect the communications.  Symmetric encryption: it uses the same key for coding and decoding. The key is shared by the emitter and the receiver of the message, using it the former to code the message and the latter to decode it.  Asymmetric encryption: it uses two different keys, one for coding and the other for decoding. The key to encode is shared and public; the key to decode is secret and private. The emitter uses the public key of the receiver to encrypt the message and, the receiver, when receiving it, uses its own private key to decrypt it. Protection of the communications  Firewalls: A firewall is an element that controls and filters the network connections of a machine or set of machines. It is a basic prevention mechanism against external intrusion threats. 

Proxy servers: A proxy is a computer that serves as intermediary for a client and a destination. When a client wants information, connects with the proxy server instead of doing it with the destination server. The proxy server connects with the destination server as though if it were the client itself and, having obtained the information sends it to the computer that started the request.

BLUETOOTH This technology communicates devices through infrared waves. The infrared links are limited by space and obstacles. The fact that the infrared wavelength is so small (850-900 nm), means that it cannot be spread in the same way as radio signals do. It is commonly used in remote controls, some peripherals and other devices.

Malware is the name given to the program which aims at infiltrating or harming a computer without the knowledge of the user. -Steal information. -Create networks of zombie computers or botnet. -Sell false security solutions to solve the problem. -Not allow start the computer or cipher the content Types of malwareViruses A computer virus is a malware aimed at altering the normal working of the computer, without the permission or the knowledge of the user. Viruses replace executable files with others infected by the code of it. Viruses act when an infected program is executed Worms Are very similar to viruses but the great difference is that they spread by themselves, without the need of being executed by a human being. This makes worms extremely dangerous since they have the ability of replicating in the system. Trojans Are programs that masquerade and hide a non-desired function in an innocent-looking program. Types of trojans Backdoors: modify the system in order to allow a hidden door to access it.  Keyloggers: store, inadvertently, all user typing that it performs. Spyware: once installed automatically sends outside information from the user´s computer. Adware: are advertising programs that show ads, generally through pop ups or pages of the browser.

Protection systems against viruses and Trojans  Antivirus: are programs designed to detect and remove harmful software. They have two basic threat detection mechanisms. Antispyware: although nowadays the antiviruses are designed to extend their protection against any kind of malware, it is sometimes necessary to use specific programs to detect spyware that complement the activity of the antivirus. Propagation of malware  Exploiting vulnerability or a security breach, either of the Operating System or of some installed program.  Social engineering. That is, convincing the user to perform a specific action like installing some program or drivers believing that it is installed a necessary element, or accessing a web with malicious content. malicious file that may reach as an attachment of an email message, through a P2P network or a file downloaded from Internet or a shared folder. Using removable devices like USB sticks. Simply the fact of connecting a USB stick to a computer can infect it. To avoid it a specific antimalware for USB sticks can be used or disabling the auto-start function of these devices.