Input and Output Management in Device Management

INPUT AND OUTPUT MANAGEMENT Device Management : By device management , we mean the management of input and output device . These include actual device such as printer , card reader , magnetic tape , keyboard , disk and drums etc. and supporting unit such as control units , control channels . The basic function of device management are : Keeping track of the status of each attached devices. Deciding on policy to determine who get a resource , for how long and when. Allocation physically assigning a device to process. 1. 2. 3.

DEDICATED DEVICES A dedicated device is allocated to a job for the jobs entire duration . Some device lend themselves to this form of allocation . It is difficult , for example , to share a card reader tape , or printer . If several user want to use the printer at the same time , would they cut up there appropriate output and paste it together .

SHARED DEVICES There are some device such as disks , drums that may be shared con currently by more than one job . Information stored on a direct access device is directly accessible . Several processes can be read form a single device essentially at the same times . The management of a shared device can be become quite complicated , particularly if utmost efficiency is desired . There are two problem associated with the use of shared device must be handled by the operating system . Since there is a little interference caused by multiple jobs sharing access to the device let to process simultaneously request a read form disk . A , so some mechanism must be employed to determine which request should be handled first . This may be done by the software or by the hardware . Policy for establishing which processes request is to be satisfied first , might be based on . (a) A priority list. (b) The objective of achieving improved system output.

INPUT/OUTPUT DEVICES As you know , the computer works on input process - process output cycle . The user firstly feeds the data to computer in form of understandable by him . The data are converted into machine language that is understandable by the input unit of the computer . The input data are stored in memory from where they are taken out for processing and after processing , the is generated . The generated result is sent to output unit where it is converted into the user understandable form . These section deals with the variety of input output device and storage device .

INPUT DEVICES Input device are the device used to supply input to the computer . It is the first phase of the data processing process . There is a variety of device in the category . We will have a brief look at commonly used input device one by one. (a) Keyboard : This is most common and popular device . It is used key in the character by typing them . A standard 104 keys is most common and it is contain following keys: Numeric keys Character keys Special keys Function keys 1. 2. 3. 4. (b) Mouse : it is another popular point input device generally used in graphic use of interface system in which we interact with computer through picture . A mouse is pointing device which is used to supply input through a graphical a representation called cursor .

INPUT DEVICES (c) Microphone : microphones are plugged into sound input socket on the sound card of the computer . As more and more people have started using computer for listening , recording music , internet telephony , chatting microphone is one of the most commonly device to input voice . It translates the analog voice signal into computer understandable digital form . (d) Light pen : you must have seen the commentators marking a portion of screen while explaining a particular area of the field set a particular shot of a batsman in a cricket match . This is done with light pen . It is type of pointing devices that is used to choose a displayed menu on screen for a program . Light pen does not emit light; rather it react to light through a photo sensitive detector at its base . (e) Scanners : scanners are the other very popular other input device they are used to transfer printed or handmade picture or drawing into computer . A broad variety of scanners has specific area of application . (f) Joystick : the device is particularly used to for user who uses computer for playing games . It is generally a vertical stick having various buttons mounted on it for various kinds of inputs . The function of these button may change depending upon the game you are playing .

OUTPUT DEVICES Output is the third phase of processing cycle . In the information is displayed in form hard or soft after the processing of data . Output device are the devices used for displaying this output . The output devices may be divided in two board categories. . Soft copy output . Hard copy output Soft copy : this is the type of output which is available to the user till the computer is powered on . This cannot be referred at any point of time for ex. The output we seen on screen of our monitor is available till the computer is on. Hard copy : it is a type of output which can be read directly and immediately this form of output referred at any point of time without any regard to computer . This type of output is generally produced on a paper printed form this permanent type of output. 1. 2.

OUTPUT DEVICES . Soft copy devices : we have separate devices for both types of outputs . (a) Computer , monitor (b) Flat panel display . Hard copy devices : these are the device which produce hardcopy of the output , generally on paper . These are very slow in operation as compared to the monitor . The main class of devices , which is discussed in this section , is printers .

PRINTERS Printer are the output device , which produce hard copy of output generally on paper . It the most common medium to distribute text and graphics to other . The quality of output is analysed in terms of dot per inch i.e. how many dots a printer prints on a unit area of a paper . More are dots , better is output quality . Today , printers offers many options about the choice of resolution , which can be chosen by user . Impact printer Non-impact printer 1. 2.

IMPACT PRINTERS These are printers that prints by having a physical contact between the printer head and paper to print the desired image . There are two sub categories of printers in the class i.e. serial printer or character printer and line printer . Dot matrix printer . Daisy wheel printer . Line printer . 1. 2. 3. Chain printer . Drum printer . 4. 5.

NON-IMPACT PRINTERS This is the category of printer which is print without any physical contact with the paper . The printers belonging to the category generally print by using electric , heat and pressure or laser technology . Non-impact printer have greater resolution then the impact printer . The most important property which is not there in impact printer as that most not of the non- impact printers can print coloured outputs . Inkjet printer 1. Laser printer Plotters Thermal wax printers 2. 3. 4.