Input and Output Devices PDF

## 2 INPUT AND OUTPUT DEVICES - contain almost no data redundancy (that is, data which is duplicated) therefore it is not possible to guard against badly printed or damaged barcodes - QR codes are easier to read; they do not need expensive laser or LED (light emitting diode) scanners like barcodes...

## 2 INPUT AND OUTPUT DEVICES - contain almost no data redundancy (that is, data which is duplicated) therefore it is not possible to guard against badly printed or damaged barcodes - QR codes are easier to read; they do not need expensive laser or LED (light emitting diode) scanners like barcodes - they can be read by the cameras used on smartphones and tablets - It is easy to transmit QR codes either as text messages or images. - It is also possible to encrypt QR codes, which gives them greater protection than traditional barcodes. ### Disadvantages of QR codes - More than one QR format is available. - QR codes can be used to transmit malicious codes; known as **attagging**. Because there are a large number of free apps available to a user for generating QR codes, that means anyone can do this. It is relatively easy to write malicious code and embed this within the QR code. When the code is scanned, it is possible the creator of the malicious code could gain access to everything on the user's smartphone/tablet (for example, photographs, address book, stored passwords, etc.). The user could also be sent to a fake website, or it is even possible for a virus to be downloaded. ## 2.3 Output devices and their uses As the name suggests, these are devices that usually show the result of computer processing in a format that can be understood by a human (for example, on a monitor or printed on paper). However, some output devices are part of a control system. In these examples, the computer is controlling a process and sends signals to these output devices. ### 2.3.1 Monitors (screens) In this section we will consider two types of monitor: - The cathode ray tube (CRT) monitor - LCD (or TFT) screen (TFT means 'thin film technology'; a general term for modern thin screens). While CRT monitors have just about been phased out everywhere, they are included here because these are the only type of device which allows the use of light pens (see Section 2.1.11). Consequently, some companies using CAD still use large CRT monitors to enable the use of light pens as part of the drawing environment. ### CRT monitors Cathode ray tube (CRT) monitors are the least expensive type of monitor, although they are becoming increasingly rare as LCD monitors are now taking over. They come in various sizes and make use of an electron gun firing against a phosphor screen. The picture is made up of tiny dots which are coloured red, green or blue - the intensity of each coloured dot makes up the vast range of colours interpreted by the eye. The image shows a typical CRT monitor, with the following text: - Fi - m The number 44 is visible in the bottom corner of the image.