Domande Infotech

Domande Infotech

What is a Computer?

The computer is an electronic machine which can accept data in a certain form, process the data and give the results of the processing in a specified format as information. A computer is made up of two parts: Hardware, which is made up by electronic and mechanical parts and Software, which consists in information in the form of data and programs. Hardware is divided as well in three parts: The Cpu (Central Processing Unit), the main memory and the peripherals. The Cpu is called also the 'brain' of the computer, its function is to execute program instructions and coordinate the activities of all the other units. The main memory holds the instructions and data which are currently being processed by the cpu. The peripherals are the physical units attached to the computer. They include storage devices and Input/Output devices. Storage devices, like floppies, hard and optical disks provide a permanent storage of data and programs. Input devices enable data to go into the computer's memory like the mouse and the keyboard, and Output devices enable us to extract the finished product from the system.

What can you do with a computer?

Computers can be used in many fields. We can use computers to perform financial transactions or mathematical operations, to keep records of large collections of data such as lists or inventories. Computers allow us to type and print any kind of document, letters, memos and we can also communicate with other computers around the world.For instance, we can use E-mails, which are our personal connection to the Internet, to exchange messages with people all over the world, including texts, pictures and even audio and animation. Thanks to Internet relay chat, we can carry out real time conversations by typing messages in chat sessions. Computers can be used also in banks to store information about the amount of money heald by each client, to carry out  financial transactions at high speed and to control also automatic cash dispensers which by the use of a personal coded card dispense money to clients.We can also use computers to carry out researches of any kind on the Internet by the use of research engines like Google, and we can also buy and sell every kind of goods on Internet sites like E-Bay.

What is the difference between Hardware and Software?

Hardware consists in the electronic and mechanical parts that make up a computer system while Software are information in the form of data and programs. Hardware is divided as well in three parts: The Cpu (Central Processing Unit), the main memory and the peripherals. The Cpu is called also the 'brain' of the computer, its function is to execute program instructions and coordinate the activities of all the other units. The main memory holds the instructions and data which are currently being processed by the cpu. The peripherals are the physical units attached to the computer. They include storage devices and Input/Output devices. Storage devices, like floppies, hard and optical disks provide a permanent storage of data and programs. Input devices enable data to go into the computer's memory like the mouse and the keyboard, and Output devices enable us to extract the finished product from the system.

4)What do you know about the central processing unit?

The Central Processing Unit is called also the 'brain' of the computer, its function is to execute program instructions and coordinate the activities of all the other units.The Cpu consists of three main parts:

The Control Unit; which examines the instructions in the user's program, interprets each instruction and makes the circuits and the rest of the components to be activated to execute the functions specified.

The Arithmetic logic unit also called ALU, which performs mathematical calculations and logical operations.

The Registers, which are high speed units of memory used to store and control information. One of these registers is the Program Counter which keeps track of the next instruction to be performed in the main memory. Another is the instruction register which holds the instruction that is currently being executed.

Write something about the main peripherals of a computer system.

The peripherals are the physical units attached to the computer. They include storage devices and Input/Output devices. Storage devices, like floppies, hard and optical disks provide a permanent storage of data and programs.Input devices are the pieces of hardware which allow us to enter information into the computer;the most  common input devices are the mouse and the keyboard. The mouse allows us to control the cursor and move around the screen very quickly. As we move the mouse on our desk, the pointer on the screen moves in the same direction. The pointer usually looks like an I-bar, an arrow or a pointing hand, depending on what we are doing. The keyboard is made up of typewriter keys for letters, numbers and line controllers, and it may also have function keys for special purposes. Output devices are units of hardware which shows the results produced by the computer. For instance, we can see the results on the monitor or print them onto paper by means of a printer.

What is the ASCII Code?

ASCII stands for American Standard Code for Information Interchange which is a standard system for the binary representation of characters. There are 256 different ways of combining 0 and 1 bits in a byte, so they can give us 256 different signals. However the ASCII code only uses 128 bytes to represent characters, the rest of the bytes are used for other purposes. The first 32 codes are reserved for characters such as the return key, escape and others. Each letter of the alphabet, and many symbols as well as the ten numbers, have ASCII representations. What makes this system powerful is that these codes are standard.

What is an input device?

Input devices are the pieces of hardware which allow us to enter information into the computer;the most  common input devices are the mouse and the keyboard. The mouse allows us to control the cursor and move around the screen very quickly. As we move the mouse on our desk, the pointer on the screen moves in the same direction. The pointer usually looks like an I-bar, an arrow or a pointing hand, depending on what we are doing. The keyboard is made up of typewriter keys for letters, numbers and line controllers, and it may also have function keys for special purposes. Another input device is the scanner which has a flat surface that scans images as a series of dots and introduces the information into the computer's memory.

What is an output device?

Output devices are units of hardware which shows the results produced by the computer. For instance, we can see the results on the monitor or print them onto paper by means of a printer.

There are many types of monitors : The cathode ray tube of a monitor is very similar to that of a tv set; inside the tube there is an electronic beam which scans the screen and turns on or off the pixels that make up the image. Lcd which stands for liquid crystal display is a flat screen monitor that has the advantage of requiring less space and giving a very clear image eliminating the screen flicker. An Lcd uses a grid of crystals and polarizing filters to show the image; the crystals block the light in different amounts to generate the dots in the image. The printer is an output device which converts data into printed form. There are various types of printers: One common type is the ink-jet printer; it operates by projecting small ink droplets onto paper to form the required image, this type of printer is quite fast, silent and not so expensive. Laser printers produce output at great speed and with a very high resolution; they scan the image with a laser beam and transfer it to paper with a special ink powder.

What is the difference between an input and an output device?

Both input an output devices are part of the peripherals of a computer system, that is the physical units attached to the computer.Input devices are the pieces of hardware which allow us to enter information into the computer while Output devices are units of hardware which shows the results produced by the computer.

What is the mouse useful for?

The mouse is the most common input device; it allows us to control the cursor and move around the screen very quickly. As we move the mouse on our desk, the pointer on the screen moves in the same direction. The pointer usually looks like an I-bar, an arrow or a pointing hand, depending on what we are doing. A mouse has one or more buttons to communicate with the computer. For instance, if we want to place the insertion point or choose a menu option, we just click by pressing and releasing on the mouse button, and the option is chosen. The mouse is used to select text and items on the screen, we can highlight text to be deleted, or we can select an item from a check-box or questionnaire. The mouse is widely used in graphics and design. When we want to move an image, we position the pointer on the object we want to move, press the mouse button and drag the image to a new location on the screen.The mouse is also used to start a program or open a document by putting the pointer on the file name and double clicking on the name that is rapidly press and release the mouse button twice.

What is a scanner?

A scanner is an input device which reads images and converts the printed text or pictures into electronic codes that can be understood by the computer.With a flatbed scanner, the paper with the image is placed face down on a glass screen similar to a photocopier.Beneath the glass are the lighting and measurement devices. Once the scanner is activated, it reads the image as a series of dots and then generates the digitized image that is sent to the computer and stored as a file. A colour scanner operates by using three rotating lamps, each of which has a different coloured filter: red, green and blue. The resulting three separate images are combined into one by appropriate software.

What is a digital camera?

A digital camera takes photos electronically and converts them into digital data. It doesn't use the film found in a normal camera; instead it has a special light sensitive silicon chip. Photographs are stored in the camera's memory before being sent to the computer. Some cameras can be also connected to a printer ora Tv set, to make viewing images easier.

What is a digital video camera?

A digital video camera also called camcorder, records moving pictures and converts them into digital data that can be stored and edited by a computer with special video editing software. Digital video cameras are used by home users to create their own movies or by professionals in computer art and video conferencing. They are also used to send live video images via the Internet, then they are called Web cameras or webcams.

Write something about the monitor

The monitor also called visual display unit is one of the most common output device which displays the result produced by the computer. The characters and pictures that we see on the screen are made up of dots also called picture elements or pixels. The total number of pixels in which the display is divided both horizontally and vertically is known as the resolution. If the number of pixels is very large we obtain a high resolution display and therefore a sharp image. If the number of pixels is small a low resolution is produced. There are various types of monitors : The cathode ray tube of a monitor is very similar to that of a tv set; inside the tube there is an electronic beam which scans the screen and turns on or off the pixels that make up the image. Lcd which stands for liquid crystal display is a flat screen monitor that has the advantage of requiring less space and giving a very clear image eliminating the screen flicker. An Lcd uses a grid of crystals and polarizing filters to show the image; the crystals block the light in different amounts to generate the dots in the image.

Describe the most common printers in use

The printer is an output device which converts data into printed form. There are various types of printers: One common type is the ink-jet printer; it operates by projecting small ink droplets onto paper to form the required image, this type of printer is quite fast, silent and not so expensive. Laser printers produce output at great speed and with a very high resolution; they scan the image with a laser beam and transfer it to paper with a special ink powder. Thermal printers use heat, a special kind of paper and electrosensitive methods. They are silent and considered to be inexpensive. Imagesetters can produce very high resolution output on paper or microfilm. They are extremely fast and although they produce the highest quality output they have a disadvantage: they are too expensive for homes or small offices. Plotters are a special kind of printer which use ink and fine pens held in a carriage to draw very detailed designs on paper. They are used for construction plans, engineering drawings and other technical illustrations.

What is a floppy disk?

A floppy disk is a magnetic drive; it's so called because it consists of flexible plastic material which has a magnetizable surface. The surface of a disk is divided into concentric circles or tracks, which are then divided into sectors. When we insert a blank disk into a disk drive, it must be initialized or formatted before information can be recorded onto it. This means that magnetic areas are created for each track and sector along with a catalogue or directory which will record the specific location of files. When we save a file, the operating system moves the write heads of the disk drive towards empty sectors, record the data and writes an entry for the directory. Later on, when we open that file, the Operating system looks for its entry in the directory, moves the write heads to the correct sectors and reads the file into the Ram area.

What is the hard disk?

Hard disks are magnetic drives which work in the same way as floppies but they have important advantages; they can hold much more data and spin at higher speed so we can store and retrieve information much faster than with floppies. The speed at which a hard drive finds data is called 'access time' or seek time.The average access time is measured in milliseconds, most hard drives have an access time of 8 to 14 ms. We have to distinguish between access time and data transfer rate because data transfer rate depends also on the power of our pc. If we only use word processing programs we will need less storage capacity than if we use sound and animation programs. If we need an extra hard drive we should consider the type of mechanism. There are internal and external drives which are both rigid disks sealed into the drive unit either within or attached to the computer. Another type of hard drive, known as removable aloows us to record data on cartridges which can be removed and stored off line for security purposes.Some systems allow us to back up our entire Pc on one disk.

What do you know about Optical disks and drives?

Optical disks can store information at much higher densities than magnetic disks; they are ideal for multimedia applications where images, animation and sound occupy a lot of disk space. Besides they are not affected by magnetic fields, this means that they are secure and stable, they can be tranported through airport metal detectors without damaging the data. However optical drives are slower then hard drives. There are various types of optical drives:

CD ROM systems offer from shareware programs to dictionaries, enciclopedias, multimedia databases and much more.One CD ROM disk can replace about 300,000 pages of text which represents a lot of savings in distributing materials and corporate databases.CD ROM technology has a disadvantage, we cannot write anything onto a Cd Rom disk, we can only read it.

CD Recorders come in 2 different forms: CDR and CDRW. CDR machines record on CDR disks allowing us to create and duplicates Cd's. Thay are used to backup hard disks or to distribute and archive information. CDRW or rewritable disks can be erased and re used just as we would do with a hard disk.

DVD or digital versatile disk can hold 17 GB about 25 times an ordinary CDROM. For this reason it can store a large amount of multimedia software and complete movies in different languages.However DVDROM's are read only devices; to avoid thois limitation companies also produce DVDR and DVD rewritable disks.

Magneto Optical drives use both a laser and an electromagnet to record information. MO disks are rewritable, as they can be written to, erased and then written again. They are ideal for backup and portable mass storage.

What is an operating system?

The Operating system is the most important type of software. It is usually supplied by the manufacturers and includes a set of programs and files that control the hardware and software resources of a computer system. It controls all the elements that the user sees and it communicates directly with the computer. In most configurations the Operating System is automatically loaded into the RAM section when the computer is started up.There are many operating systems like:

MS DOS which was developed by Microsoft in 1981 for all IBM PC compatibles.Today it is used in old Pcs; it is a text based Operating system, as we communicate with the computer by typing commands that exist within a library.

Windows which is used by most home Pcs, it includes many versions like Windows 98, Windows 2000 and Windows XP which is an update to all Windows versions with a new visual design, it is more secure and reliable than other versions and it offers support for the latest technologies.

MAC OS ; large part of this OS are inside the system file.It offers Internet capabilities, support for Java and Airport technology for wireless connections.

Unix,was designed to be a multi-tasking system, it is written in C language.

Linux, is protected under the General Public Licence, it is the open source multi tasking operating system.

What do you know about the graphical interface?

A Graphical interface is an operating environment based on graphics; the term user interface refers to the standard procedures the user follows to interact with a particular computer. While in the past only experts used computers memorizing and typing a lot of commands to respond to single prompts , now computers are used by all kinds of people, that is because computers running under an attractive interface stimulate users to be more creative and produce high quality results which has a major impact on the general public. A graphical user interface saves a lot of time because we don't need to memorize commands in order to execute an application, we only have to point and click so that its content appears on the screen. Today the most innovative GUI's are the Macintosh, Microsoft windows and IBM OS/ 2 Warp. These platforms include a similar features: a desktop with icons, windows and folders, a printer selector, a file finder, a control panel and various desk accessories.

21)What can you do with a database?

With a database we can store, organize and retrieve a large collection of related information on computer. Information is entered on a database via fields. Each field holds a separate piece of information and the fields are collected together into records. Records are grouped together into files which hold large amounts of information. Files can be easily updated, we can always change fields, add new records or delete old ones. With the right database software we are able to keep track of stock, sales, market trends, orders, invoices and many more details that can make our company successful. Another feature of database programs is that we can automatically look up and find records containing particular information. We can also search on more than one field at a time.