Manual Completo de Sistemas Operativos, Hardware e Informática

Ejercicios de Escucha y Comprensión

Try to answer these questions: 1 How does he spend his working week? He had day release to attend college one day a week in the first two years of his apprenticeship and he’s got two days a week in his last year.

2 How long will his apprenticeship last? His apprenticeship lasts for three years. I’m in his final year now. 3 What sorts of skills will he acquire? He’s learned a lot of practical skills from the on-the-job training, things like working in teams, problem-solving, communication skills and using new technologies at work, as well as engineering subjects. This year he’s completing an HNC, a Higher National Certificate, in Engineering.

Listen again and answer these questions. 1 What does Stuart’s company make? They make everything from small components for medical equipment to large water pipes - the blue ones which are replacing metal pipes everywhere. 2 What stage in his apprenticeship is Stuart at? He’s learned things like working in teams, problem-solving, communication skills and using new technologies at work, as well as engineering subjects.

3 Why is there a lot of paperwork? There’s quite a lot of paperwork because he has to complete forms to show he’s reached the right standard. 4 Why do you think he has two days a week at college now? Because it’s his last year. 5 When does he study? At home in the evenings and at weekends too. 6 How much studying does he do? He’s doing about ten hours a week right now. 7 What are the attractions of becoming a team leader? He’ll be in charge of a team of six - more responsibility and better pay.

Listen to Stuart Cole, an Engineering Apprentice. Complete the blanks with the information he provides.

When I _ left _ school, I _started_ work for a plastics company, one of the biggest in the country. We _make_ everything from small components for medical equipment to large water pipes - the blue ones which are replacing metal pipes everywhere. My apprenticeship _lasts_ for three years. I’m in my final year now. It’s a good mix of work, which I get paid for, of course, on-the-job training, and _study_ at the local college. I’ve _learned_ a lot of practical skills from the on-the-job training. It’s supervised by skilled workers. There’s quite a lot of paperwork as I have to complete forms to show I’ve reached the right standard. I _had_ day release to attend college one day a week in the first two years of my apprenticeship and I’ve got two days a week in my last year. I’ve learned things like working in teams, problem-solving, communication skills and using new technologies at work, as well as engineering subjects. This year I’m _completing_ an HNC, a Higher National Certificate, in Engineering. I _like_ learning while working, but it’s quite hard work. There’s a lot of studying to do - at home in the evenings and at weekends too.

I’m _doing_ about ten hours a week right now. It’s quite hard when your friends are out having a good time. Once I’m fully qualified and have a bit more experience, I _hope_ to get promoted to team leader. That means I’ll _be_ in charge of a team of six - more responsibility and better pay.

Vocabulario Técnico y Traducciones

APPRENTICESHIP: Aprendizaje COMPUTING SUPPORT ASSISTANT: asistente del soporte técnico informático SKILLED WORKERS: Trabajador cualificado/experto

PROBLEM-SOLVING: Resolución de problemas IN CHARGE OF: Responsable de / a cargo de SKILLED WORKERS: Trabajador cualificado/experto

TRAINING / JOB-TRAINING: Prácticas FULLY QUALIFIED: Altamente cualificado

Conversaciones de Soporte IT y Entrevistas

Guy: IT Helpdesk, can I help you?                                              INTERVIEWER: What do you like most about your job?

Harry: Hi. I'm starting work here today and I need to login ANNE: I like, I like all aspects of the job. It’s good to …. It’s varied so there’s lots of interest.

to the company network. Can you help me?                               INTERVIEWER: Are you ever bored?

Guy: Sure. What's your employee number?                                 ANNE: No, not really, because it’s never the same thing over and over again; it’s different each time.

Harry: It's pt4600982.                                                                         INTERVIEWER: What kind of problems are there? What kind of difficulties do people have?

Guy: What's your name and date of birth, please?                    ANNE: People have problems with the hardware, often with printers… paper jamming. They also have Harry: It's Harry Bandwidth...and my date of birth is 14th August, 1972. problems finding options in the programs. Mostly with word processing.

Guy: Great...thanks Harry. You're in our accounting team, right?           INTERVIEWER: Are there any other hardware problems?

Harry: That's right.                                                                                           ANNE: Occasionally a computer freezes … it hangs or freezes. It’s usually a memory problem.

Guy: Can you please enter some details on your computer for me?     INTERVIEWER: Is it always the machine or is it sometimes the user?

Harry: What do you need?                                                                ANNE: Sometimes it’s the user. The printer isn’t switched on, or there’s no paper.

Guy: Firstly, your username is H BANDWIDTH and                              INTERVIEWER: How do you keep in touch with what’s new in computing? It’s changing all the time.

your password is 'accounting'. Enter them now please.     ANNE: Yeah, by the time you read something, it’s out of date. Magazines are good for finding out what’s Harry: Okay.                                                                                      new on the scene. The Internet also has information about new developments.

Guy: You need to change your password right away, so think of a new password and enter it twice.             INTERVIEWER: Do you ever go on courses?

Harry: Okay...I've done that.                                                                                                                ANNE: Yes, they’re a good way to keep up.

Guy: You're now set-up on the company network. Can I help you with anything else?             INTERVIEWER: What kind of courses?

Guy: I'll help you install that software now.                                ANNE: Well, operating systems change, so courses about the different functions on the

Harry: Thanks.

Guy: Can you see a link on your computer? operating system. And then there’s the programs that people use, like the word processors, and

Harry: Yes! the spreadsheets and databases. And the best way to understand them is by taking a course and trying them out yourself. Guy: Can you see a link on your computer?

Guy: Just click that link now. Have you done that?

Harry: Yes.

Guy: Click the download button.

Harry: It's downloading now!

Guy: The file will take about two minutes to download. Then you can install it.

Harry: That's excellent.

Guy: Can I help you with anything else?

Harry: No thanks.

Guy: If you need us again, just call 13 0199 or go to the IT website.

Harry: Great. Thanks for your help.

Guy: You're welcome. Have a good day.

Reading Task y Carta de Presentación

READING TASK: Reference_¹: Application for Network In _Response_² to the advertised position for a Network Designer in the Telecommunications Engineering Journal on 5 March 2011, I am writing to ask you to consider my _experience_³. I am looking for the opportunity to gain experience in this field. I gained hands-on _ability_⁴ in switching and transmission while studying for my NVQ* in Manchester and was fortunate enough to spend six months in Sweden with Telia as part of an exchange programme. While there, I worked on maintenance and fault-finding at the exchanges as a Network Technician and was given _application_⁵ for implementing new systems. I gained valuable experience of working as part of a _team_⁶ and in communicating with others. I am very interested in joining a leading telecoms company such as Anglo Telecom. My NVQ results show that my technical _ability_⁷ is excellent and I am very conscientious about meeting deadlines. I have excellent computing skills and a very positive attitude to learning new skills. I would appreciate the _opportunity_⁸ to meet you to discuss my application and look forward to hearing from you.

Glosario de Problemas y Componentes

PAPER JAMMING: atasco de papel    FINDING OPTIONS IN PROGRAMS: encontrar opciones en los programas    VIRUSES: virus     COMPUTER FREEZES: bloqueo/cuelgue    HARD DISK CRASHES: fallo en disco duro     PRINTER SWITCHED OFF: impresora apagada     NO PAPER IN THE PRINTER: no papel en la impresora     PEOPLE FORGET THEIR PASSWORDS: personas que olvidan sus contraseñas     PRE-LOADED: Preconfigurados     POP UP: emerger     DEVELOPED: desarrollados     DEVICE: dispositivo     SCRAP: desechar    IT MANAGES: gestiona     TASK: función     CENTRAL PROCESSING UNIT: CPU     APPLICATION PROGRAM INTERFACE: API     USER INTERFACE: UI     RANDOM ACCESS MEMORY: RAM     SERIAL ACCESS MEMORY: SAM     INTEGRATED CIRCUIT: IC DYNAMIC RANDOM ACCESS MEMORY: DRAM     GRAPHICAL USER INTERFACE: GUI   NO TONER IN THE PRINTER: no tinta en la impresora     READING BOOKS: leyendo libros     READING COMPUTER MAGAZINES: leyendo revistas de ordenadores    SPEAKING TO OTHER TECHNICIANS: hablando con otros técnicos     USING THE INTERNET: usando Internet    TAKING COURSES: tomando clases/haciendo cursos     TRYING PROGRAMS HERSELF: probando sus propios programas     READING NEWSPAPERS: leyendo periódicos

1 What kind of work does Anne do? Computing Technical 2 What does she like most about the job? She likes all aspects of the job. It’s varied 3 What kinds of problems do people have with hardware? Often with printers… paper jamming. They also have problems finding options in the programs. Mostly with word processing. 4 Why do computers freeze? There is a memory problem fault/failure 5 How does she keep up with new developments in computing? Courses trying programs self-help 6 What kinds of courses does she go on? Courses about the different functions on the operating system and then there’s the programs that people use, like the word processors, and the spreadsheets and databases and the best way to understand them is by taking a course and trying them out yourself.

Entrevista de Trabajo para Técnico IT

Mr Jones: Good morning, my name's Steve Jones. You must be Guy.

Guy: That's right, Guy Thompson. Nice to meet you, Mr. Jones.

Mr Jones: Please, call me Steve. Take a seat.

Guy: Thank you.

Mr Jones: I've read your CV and I see you're currently working for ASL Helpdesk. Is that right?

Guy: Yes, that's right.

Mr Jones: How long have you been working there?

Guy: For two years.

Mr Jones: I see. And what were you doing before that?

Guy: I worked for a computer company in Japan.

Mr Jones: Really? How long did you spend in Japan?

Guy: One and a half years. When I came home I started at ASL Helpdesk.

Mr Jones: That's good. International experience is highly valued here. Now tell me, do you know how to provide online support?

Guy: Yes, at ASL Helpdesk I provided online support to local business and individuals.

Mr Jones: Okay, so you are used to providing advice on all sorts of problems.

Guy: Well I am used to taking calls and coping with handling all sorts of people as well.

Mr Jones: Right.

Guy: It’s a job where you need not just technical skills but also good ‘soft skills’. That means people-handling skills. You need to be able to understand how the caller feels. You have to keep calm when you’re under pressure. It’s a demanding job because you have to cope sometimes with angry people, get all the information you need to help them with their problem, work out how to solve it technically, and then explain in a clear, simple way what they can do to put things right.

Mr Jones: Very good. You seem to have the skills we're looking for. Are there any questions you'd like to ask me about the position?

Guy: Umm, yes. If I get the job, what would I be doing from day-to-day?

Mr Jones: Well, we need a new staff member for our help desk. It's a challenging position, with some management responsibilities.

Guy: Okay.

Mr Jones: Does it sound like the type of job you'd be interested in?

Guy: Absolutely, it sounds great.

Gramática Inglesa: Uso del Gerundio

(cook)__cooking__ is one of her hobbies.     (cycle)__cycling__ is fun.     (get)_getting__ a good job is not easy.    (find)_finding_ a parking space is quite difficult in this area.    (drive)_driving_ becomes more and more expensive.     No (smoke)_smoking_ in this area.     (work)_working_ overtime is quite common in this company.     (eat)_eating_ fruits and vegetables is good for your health.     (make)__making__ fun of other people is not nice.     (learn)__learning_ about other cultures makes people more tolerant.

She is good __at__ dancing.    He is crazy _about___ singing.    He concentrates __on__ physics.    They are afraid __of___ swimming in the sea.     She complains __about___ losing the match.    Sam dreams ___of/about__ being a pop star.      He is interested __in__ making friends.      My uncle is talking _about_ going on holiday by plane.      We insist __on_ cooking the dinner ourselves.     We are looking forward _to_ going out at the weekend.

We use the Gerund after the following phrases:

afraid of       miedo a                                      They are afraid of losing the match.

bad at           se me da mal
good at          se me da bien                                            John is good at working in the garden.

crazy about             loco/a por aprender                      The girl is crazy about playing tennis.

interested in            me interesa             Are you interested in writing poems?

We use the Gerund after the following phrases:

concentrate on      concentrarse en algo                 Do you concentrate on reading or writing?

insist on                insistir en                                                   The girls insisted on going out with Mark.

complain about          quejarse de                                She complains about bullying.

dream of/about            soñar con                                  Sue dreams of being a pop star.

look forward to            esperar con ilusión                                      I'm looking forward to seeing you soon.

talk about                     hablar de                                  They often talk about travelling to New Zealand.

We use the Gerund after the following verbs and phrases:

don’t like / dislike / hate    odiar             We don’t like / dislike / hate reading poems.

like / enjoy / love      gustar / encantar    I like / enjoy / love playing chess.

Suggest       sugerir                                          She suggested flying to Cairo.

can’t help      no poder evitar                                               He can’t help falling in love with her.

Cycling is good for your health. He’s afraid of going by plane. Before going to bed he turned off the lights. I enjoy cooking. I am looking forward to seeing you again.

Sistemas Operativos: Funcionamiento y Tipos

Most desktop or laptop PCs come pre-loaded with Microsoft Windows. Macintosh computers come pre-loaded with Mac OS X. Many corporate servers use the Linux or UNIX operating systems. The operating system (OS) is the first thing loaded onto the computer -- without the operating system, a computer is useless. La mayoría de los portátiles o sobremesa vienen preconfigurados con MS Windows, los Macintosh vienen con Mac OS X, muchos servidores utilizan Linux o UNIX. El S.O. es lo primero que se carga en el ordenador, sin un S.O. el ordenador es inservible.

More recently, operating systems have started to pop up in smaller computers as well. If you like to tinker with electronic devices, you're probably pleased that operating systems can now be found on many of the devices we use every day, from cell phones to wireless access points. The computers used in these little devices have gotten so powerful that they can now actually run an operating system and applications. The computer in a typical modern cell phone is now more powerful than a desktop computer from 20 years ago, so this progression makes sense and is a natural development. Últimamente los sistemas operativos han empezado a emerger en ordenadores más pequeños también; si te gusta trastear con los dispositivos electrónicos, probablemente te gustará que los S.O. se puedan encontrar en muchos dispositivos de todos los días. Desde los móviles a los puntos de acceso inalámbricos, los ordenadores que se usan en estos pequeños dispositivos son tan potentes que ahora pueden hacer funcionar un S.O. y las aplicaciones. El ordenador de un móvil es más potente que un ordenador de sobremesa de hace 20 años, por eso esta evolución tiene sentido y es un desarrollo natural. The purpose of an operating system is to organize and control hardware and software so that the device it lives in behaves in a flexible but predictable way. What is an Operating System? All desktop computers have operating systems. The most common are the Windows family of operating systems developed by Microsoft, the Macintosh operating systems developed by Apple and the UNIX family of operating systems (which have been developed by a whole history of individuals, corporations and collaborators). There are hundreds of other operating systems available for special-purpose applications, including specializations for mainframes, robotics, manufacturing, real-time control systems and so on. Todos los ordenadores de sobremesa tienen sistemas operativos; los más comunes son la familia Windows desarrollados por Microsoft, los S.O. Macintosh desarrollados por Apple, y los sistemas operativos de UNIX. Estos han sido desarrollados por una legión entera de individuos, corporaciones y colaboradores. Hay otros S.O. disponibles con aplicaciones especiales, entre las que se encuentran: especializaciones para macroordenadores, robótica, fabricación, sistemas de control de tiempo real, etc.

In any device that has an operating system, there's usually a way to make changes to how the device works. This is far from a happy accident; one of the reasons operating systems are made out of portable code rather than permanent physical circuits is so that they can be changed or modified without having to scrap the whole device. En cualquier dispositivo que tenga un S.O. existe normalmente una manera de realizar cambios en su funcionamiento. Esto no ocurre por casualidad; una de las razones por la que los S.O. se hacen de código portátil en vez de circuitos físicos permanentes es para que se puedan cambiar o modificar sin tener que desechar el dispositivo entero.

For a desktop computer user, this means you can add a new security update, system patch, new application or even an entirely new operating system rather than junk your computer and start again with a new one when you need to make a change. As long as you understand how an operating system works and how to get at it, in many cases you can change some of the ways it behaves. Para un usuario de ordenadores de sobremesa esto conlleva que se pueda añadir una nueva actualización de seguridad, un parche al sistema, una aplicación nueva o incluso un S.O. completamente nuevo, en lugar de tirar a la basura el ordenador y comenzar con uno nuevo cuando se necesita hacer un cambio. Si entiendes cómo funciona un sistema operativo y cómo llegar a él, en muchos casos puedes cambiar algunas de las formas en las que actúa.

Funciones del Sistema Operativo

What exactly can an operating system do? ¿Qué puede hacer exactamente un sistema operativo? Operating System Functions

At the simplest level, an operating system does two things: En los niveles más simples, un sistema operativo hace dos cosas: 1) It manages the hardware and software resources of the system. In a desktop computer, these resources include such things as the processor, memory, disk space and more (On a cell phone, they include the keypad, the screen, the address book, the phone dialer, the battery and the network connection). Gestiona los recursos del soporte físico y software del sistema. Estos recursos incluyen el procesador, memoria, espacio de disco, procesador… En un móvil se incluye el teclado numérico, la pantalla, la agenda, la batería y la conexión de red. 2) It provides a stable, consistent way for applications to deal with the hardware without having to know all the details of the hardware. Proporciona una forma sólida y consistente para que las aplicaciones actúen con el hardware, sin tener que conocer todos los detalles del hardware.

The first task, managing the hardware and software resources, is very important, as various programs and input methods compete for the attention of the central processing unit (CPU) and demand memory, storage and input/output (I/O) bandwidth for their own purposes. In this capacity, the operating system plays the role of the good parent, making sure that each application gets the necessary resources while playing nicely with all the other applications, as well as husbanding the limited capacity of the system to the greatest good of all the users and applications. La primera función, gestionar los recursos de hardware y software, es muy importante ya que distintos programas y métodos de entrada compiten por la atención de la unidad central de proceso (CPU) y exigen memoria, almacenamiento y ancho de banda de entrada/salida (I/O) para sus propósitos. En esta capacidad de gestionar los recursos, el S.O. hace el papel del buen padre, asegurándose de que cada aplicación consigue los recursos necesarios mientras interactúa con el resto de aplicaciones, así como economizando la capacidad limitada del sistema para el mayor beneficio de todos los usuarios y aplicaciones.

The second task, providing a consistent application interface, is especially important if there is to be more than one of a particular type of computer using the operating system, or if the hardware making up the computer is ever open to change. A consistent application program interface (API) allows a software developer to write an application on one computer and have a high level of confidence that it will run on another computer of the same type, even if the amount of memory or the quantity of storage is different on the two machines. La segunda función, proporcionar una interfaz de aplicación consistente, es especialmente importante si tiene que haber más de un tipo de ordenador utilizando el S.O., o si el hardware que conforma el ordenador está abierto a modificaciones. Una sólida interfaz de programación de aplicaciones (API) permite a un desarrollador de software escribir una aplicación en un ordenador y confiar plenamente en que funcionará en un ordenador del mismo tipo aunque la cantidad de memoria o almacenamiento sea diferente en ambas máquinas. Even if a particular computer is unique, an operating system can ensure that applications continue to run when hardware upgrades and updates occur. This is because the operating system -- not the application -- is charged with managing the hardware and the distribution of its resources. One of the challenges facing developers is keeping their operating systems flexible enough to run hardware from the thousands of vendors manufacturing computer equipment. Today's systems can accommodate thousands of different printers, disk drives and special peripherals in any possible combination. Aunque un ordenador en concreto sea único, un sistema operativo ha de asegurar que las aplicaciones sigan ejecutándose cuando se produzcan actualizaciones y modificaciones. Esto es porque el S.O. —y no la aplicación— se encarga de gestionar el hardware y la distribución de sus recursos. Uno de los retos a los que se enfrentan los desarrolladores es mantener los S.O. lo suficientemente flexibles para ejecutar el hardware de los miles de vendedores que fabrican equipamiento informático. Los sistemas de hoy en día pueden acoplar miles de impresoras distintas, unidades de disco y periféricos especiales en cualquier combinación posible.

Tipos de Sistemas Operativos

Within the broad family of operating systems, there are generally four types, categorized based on the types of computers they control and the sort of applications they support. The categories are:

1) Real-time operating system (RTOS) - Real-time operating systems are used to control machinery, scientific instruments and industrial systems. An RTOS typically has very little user-interface capability, and no end-user utilities, since the system will be a "sealed box" when delivered for use. A very important part of an RTOS is managing the resources of the computer so that a particular operation executes in precisely the same amount of time, every time it occurs. In a complex machine, having a part move more quickly just because system resources are available may be just as catastrophic as having it not move at all because the system is busy.

2) Single-user, single task - As the name implies, this operating system is designed to manage the computer so that one user can effectively do one thing at a time. The Palm OS for Palm handheld computers is a good example of a modern single-user, single-task operating system.

3) Single-user, multi-tasking - This is the type of operating system most people use on their desktop and laptop computers today. Microsoft's Windows and Apple's Mac OS platforms are both examples of operating systems that will let a single user have several programs in operation at the same time. For example, it's entirely possible for a Windows user to be writing a note in a word processor while downloading a file from the Internet while printing the text of an e-mail message.

4) Multi-user - A multi-user operating system allows many different users to take advantage of the computer's resources simultaneously. The operating system must make sure that the requirements of the various users are balanced, and that each of the programs they are using has sufficient and separate resources so that a problem with one user doesn't affect the entire community of users. Unix, VMS and mainframe operating systems, such as MVS, are examples of multi-user operating systems.

User Interface (Interfaz de Usuario)

A user interface (UI) brings structure to the interaction between a user and the computer. In the last decade, almost all development in user interfaces has been in the area of the graphical user interface (GUI), with two models, Apple's Macintosh and Microsoft's Windows, receiving most of the attention and gaining most of the market share. The popular open-source Linux operating system also supports a graphical user interface. There are other user interfaces, some graphical and some not, for other operating systems. Unix, for example, has user interfaces called shells that present a user interface more flexible and powerful than the standard operating system text-based interface. Programs such as the Korn Shell and the C Shell are text-based interfaces that add important utilities, but their main purpose is to make it easier for the user to manipulate the functions of the operating system. There are also graphical user interfaces, such as X-Windows and Gnome, that make Unix and Linux more like Windows and Macintosh computers from the user's point of view. It's important to remember that in all of these examples, the user interface is a program or set of programs that sits as a layer above the operating system itself. The same thing is true, with somewhat different mechanisms, of both Windows and Macintosh operating systems. The core operating-system functions -- the management of the computer system -- lie in the kernel of the operating system. The display manager is separate, though it may be tied tightly to the kernel beneath. The ties between the operating-system kernel and the user interface, utilities and other software define many of the differences in operating systems today, and will further define them in the future.

Memoria RAM y Componentes de Memoria

RAM is the best known form of computer memory and easy to upgrade. Random access memory (RAM) is the best known form of computer memory. RAM is considered "random access" because you can access any memory cell directly if you know the row and column that intersect at that cell. The opposite of RAM is serial access memory (SAM). SAM stores data as a series of memory cells that can only be accessed sequentially (like a cassette tape). If the data is not in the current location, each memory cell is checked until the needed data is found. SAM works very well for memory buffers, where the data is normally stored in the order in which it will be used (a good example is the texture buffer memory on a video card). RAM data, on the other hand, can be accessed in any order. Similar to a microprocessor, a memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit of information -- a 0 or a 1 (see How Bits and Bytes Work for information on bits). The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state. A capacitor is like a small bucket that is able to store electrons. To store a 1 in the memory cell, the bucket is filled with electrons. To store a 0, it is emptied. The problem with the capacitor's bucket is that it has a leak. In a matter of a few milliseconds a full bucket becomes empty. Therefore, for dynamic memory to work, either the CPU or the memory controller has to come along and recharge all of the capacitors holding a 1 before they discharge. To do this, the memory controller reads the memory and then writes it right back. This refresh operation happens automatically thousands of times per second.

Teclados Tradicionales y No Tradicionales

Keyboard Basics A keyboard's primary function is to act as an input device. Using a keyboard, a person can type a document, access menus, play games,…. Keyboards can have different keys depending on the manufacturer, the operating system they're designed for, and whether they are attached to a desktop computer or part of a laptop. Most keyboards have between 80 and 110 keys, including: Typing keys, A numeric keypad, Function keys, Control keys.

The typing keys include the letters of the alphabet, generally laid out in the same pattern used for typewriters.

The numeric keypad is a more recent addition to the computer keyboard. As the use of computers in business environments increased, so did the need for speedy data entry. Since a large part of the data was numbers, a set of 17 keys, arranged in the same configuration found on calculators, was added to the keyboard.

In 1986, IBM further extended (amplió) the basic keyboard with the addition of function and control keys. Applications and operating systems can assign specific commands to the function keys. Control keys provide cursor and screen control. Four arrow keys arranged in an inverted T formation between the typing keys and numeric keypad move the cursor on the screen.

Other common control keys include (teclas de acceso rápido): Home, End, Insert (Ins), Delete (Del), Page Up (Pgup), Page Down (Pgdn), Control (Ctrl), Alternate (Alt), Escape (Esc).

Non-Traditional Keyboards

Some modifications are designed to make keyboards more portable, more versatile or just cooler: Das Keyboard is a completely black keyboard with weighted keys that require more pressure from a person's strongest fingers and less pressure from the weaker ones. (Es un teclado completamente negro con teclas ponderadas, teclado inteligente que funciona por presión/peso). The Virtual Laser Keyboard projects a representation of a keyboard onto (sobre) a flat surface. When used successfully, a person's fingers pass through the beam of infrared light above the projected surface, and a sensor interprets it as a keystroke. The True-touch Roll-up keyboard is flexible and can be rolled up to fit in a backpack or bag. Illuminated keyboards, like the Ion Illuminated Keyboard, use light-emitting diodes or electroluminescent film to send light through the keys or the spaces between keys. The Optimus keyboard has organic light-emitting diodes (OLEDs) in the keys. Users can change what letter, command or action each key represents, and the OLED can change to display the new information. With the exception of the Virtual Laser Keyboard, which has its own sensing system (sistema de detección), each of these keyboards uses the same type of technology as traditional models do to communicate with the computer.

From the Keyboard to the Computer

Many keyboards connect to the computer through a cable with a PS/2 or USB (Universal Serial Bus) connector. Laptops use internal connectors. Regardless of (adverb: in spite of) which type of connector is used, the cable must carry power to the keyboard, and it must carry signals from the keyboard back to the computer. Wireless keyboards, on the other hand, connect to the computer through infrared (IR), radio frequency (RF) or Bluetooth connections. IR and RF connections are similar to what you'd find in a remote control. Regardless of which sort of signal they use, wireless keyboards require a receiver, either built in or plugged in to the USB port, to communicate with the computer. Since they don't have a physical connection to the computer, wireless keyboards have an AC power connection or use batteries for power. Whether it's through a cable or wireless, the signal from the keyboard is monitored by the computer's keyboard controller. This is an integrated circuit (IC) that processes all of the data that comes from the keyboard and forwards it to the operating system. When the operating system (OS) is notified that there is data from the keyboard, it checks to see if the keyboard data is a system level command. A good example of this is Ctrl-Alt-Delete on a Windows computer, which reboots the system. Then, the OS passes the keyboard data on to the current application. The application determines whether the keyboard data is a command, like Alt-f, which opens the File menu in a Windows application. If the data is not a command, the application accepts it as content, which can be anything from typing a document to entering a URL to performing a calculation. If the current application does not accept keyboard data, it simply ignores the information. This whole process, from pressing the key to entering content into an application, happens almost instantaneously.

Using Virtual Laser Keyboards

If it sounds like a gadget from the future, a virtual laser keyboard sort of looks like one, too, especially when it's on full working display. They're small and sleek, weigh about two ounces (56.7 grams) and comparable in size to a pack of gum, so they can fit easily into pockets or carrying bags. Most devices either stand up straight on a rectangular base or prop up with the help of a stand that flips out from the back. Once powered up, the keyboard can connect to a smartphone, PDA or laptop via USB cable or, more commonly, Bluetooth wireless technology. These two connection options allow the virtual laser keyboard to send keystroke information to a word processing document, e-mail or any other program in question. Although they're small and convenient to carry around, you can't simply pull out the virtual laser keyboard and start typing away in any location. If you were sitting on the bus, for instance, and wanted to write a quick e-mail on your BlackBerry, you couldn't shine the device's red laser onto your lap and expect it to work properly. Virtual laser keyboards require flat, opaque and non-reflective surfaces for working projection and typing. Once you have the keyboard set up on the right type of surface, the device displays a full-size QWERTY keyboard, which typically contains 60 or more keys.

Funcionamiento de las Grabadoras de CD

How CD Burners Work

With the rise of the MP3 format, burning your own music CDs has never been so popular -- or so easy. CDs have become one of the most widely adopted data-storage mechanisms. The advent of CD burners marked a huge cultural shift. The technology made it feasible for the average person to gather songs and make their own CDs. Today, writable CD drives (CD burners) are standard equipment in new PCs, and more and more audio enthusiasts are adding separate CD burners to their stereo systems. In less than five years, CDs have eclipsed cassette tapes.

CD Basics: The Bumps

CDs store music and other files in digital form -- that is, the information on the disc is represented by a series of 1s and 0s. In conventional CDs, these 1s and 0s are represented by millions of tiny bumps and flat areas on the disc's reflective surface. The bumps and flats are arranged in a continuous track that measures about 0.5 microns (millionths of a meter) across and 3.5 miles (5 km) long. To read this information, the CD player passes a laser beam over the track. When the laser passes over a flat area in the track, the beam is reflected directly to an optical sensor on the laser assembly. The CD player interprets this as a 1. When the beam passes over a bump, the light is bounced away from the optical sensor. The CD player recognizes this as a 0.

CD Basics: The Path

The bumps are arranged in a spiral path, starting at the center of the disc. The CD player spins the disc while the laser assembly moves outward from the center of the CD. At a steady speed, the bumps move past any point at the outer edge of the CD more rapidly than they move past any point nearer the CD's center. In order to keep the bumps moving past the laser at a constant rate, the player must slow the spinning speed of the disc as the laser assembly moves outward. At its heart, this is all there is to a CD player. The execution of this idea is fairly complicated, because the pattern of the spiral must be encoded and read with incredible precision, but the basic process is pretty simple.

Reading CDs

In the last section, we saw that conventional CDs store digital data as a pattern of bumps and flat areas, arranged in a long spiral track. The CD fabrication machine uses a high-powered laser to etch the bump pattern into photoresist material coated onto a glass plate. Through an elaborate imprinting process, this pattern is pressed onto acrylic discs. The discs are then coated with aluminum (or another metal) to create the readable reflective surface. Finally, the disc is coated with a transparent plastic layer that protects the reflective metal from nicks, scratches and debris. As you can see, this is a fairly complex, delicate operation, involving many steps and several different materials. Like most complex manufacturing processes (from newspaper printing to television assembly), conventional CD manufacturing isn't practical for home use. It's only feasible for manufacturers who produce hundreds, thousands or millions of CD copies. Consequently, conventional CDs have remained a "read only" storage medium for the average consumer, like LPs or conventional DVDs. To audiophiles accustomed to recordable cassettes, as well as computer users who were fed up with the limited memory capacity of floppy disks, this limitation seemed like a major drawback of CD technology. In the early '90s, more and more consumers and professionals were looking for a way to make their own CD-quality digital recordings.

Writing CDs

In response to this demand, electronics manufacturers introduced an alternative sort of CD that could be encoded in a few easy steps. CD-recordable discs, or CD-Rs, don't have any bumps or flat areas at all. Instead, they have a smooth reflective metal layer, which rests on top of a layer of photosensitive dye. When the disc is blank, the dye is translucent: Light can shine through and reflect off the metal surface. But when you heat the dye layer with concentrated light of a particular frequency and intensity, the dye turns opaque: It darkens to the point that light can't pass through. By selectively darkening particular points along the CD track, and leaving other areas of dye translucent, you can create a digital pattern that a standard CD player can read. The light from the player's laser beam will only bounce back to the sensor when the dye is left translucent, in the same way that it will only bounce back from the flat areas of a conventional CD. So, even though the CD-R disc doesn't have any bumps pressed into it at all, it behaves just like a standard disc.