Computer input and output devices

INPUT & OUTPUT DEVICES

Key Board

  A keyboard is a most common input device.
A computer keyboard looks very much like an ordinary Typewriter keyboard, which is familiar to all of us. A computer keyboard in addition to the letter and number keys of ordinary typewriters has some special keys for special functions. A computer’s CPU can understand only electrical signals (coded pulses). When we press any key on the keyboard, the key sends a series of electrical pulses to the computer. The pattern of these pulses presents a code for that particular character. The computer receives it, interprets it and it‘ is stored in the memory.

Printers

Types of Printers. Printers can be divided into two major categories; Impact Printers and Non-impact Printers. Impact printers are those printers in which printing of a character is achieved by striking of hammers or pins through a ribbon to deposit carbon or ink onto the paper. Non-impact printers on the other hand are those printers, which print without creating any impact On the paper.

Impact printers are further categorised as Line printers and Character printers. Line printers are those printers, which print one complete line in its one print cycle. Character printers are those printers, ' which print character by character. Dot matrix printer and daisy wheel printers are the examples of Character printer.

Printers

Impact printers          

1)  Character Printer.

(i) dot matrix Printer

( ii)daisy wheel printer

2)Line printer

 (i) Chain Printer

 (ii) Drum Printer 

Operating System                       

An Operating System (OS) is n integrat . . special program Is .that is used to manage the resourcesand overall operations of computer. The OS permits the computer to supervise its own operations by automatically calling in the applications programs. translating any other special service programs, and managing the data needed to produce the output desired by the user. Thus, as Fig. 1.2 indicates, the 08 tends to isolate the hardware from the user. The user supplies applications programs and input data that are in a language and format acceptable to the OS. and receives output results. But the user is usually not too concerned with the hardware specifics of the system, or withhow the OS will direct the hardware to handle certain tasks. 

An OS is a set of programs that acts as an interface between  users and a Hardware of the computer. 

     The computer systems running under OS control today range in size from small personal computers to the largest mainframe and supercomputers. The general goal of OS developers has been to devise ways to operate a computer with minimum of idle time and in the most efficient and economical way during the executionof user’s programs. in short an Operating System performs the following three functions: 

(a) managing Devices. initiating and controlling l/O operations. 

management of memory space (in main memory as well as auxiliary memory) for the efficient storage of data. and its quick and reliable retrieval. 

(b) Controlling Programs. Scheduling, loading, initiating and supervnsmg the execution of programs. Maintaining a log of system operations. 

(c) Processing the Commands. Accepting the users commands 

carrying out.