n transmits the signals through a telephone line or a communication network to another computer. A modem on the computer at the other end of the line reverses the process. Printers generate hard copy--a printed version of information stored in one of the computer's memory systems. The three principal types of printers are daisy-wheel, dot-matrix, and laser. Other types of printers include ink-jet printers and thermal printers. SoftwareA computer's operating system is the software that allows all of the dissimilar hardware and software systems to work together. It is often stored in a computer's ROM memory. An operating system consists of programs and routines that coordinate operations and processes, translate the data from different input and output devices, regulate data storage in memory, allocate tasks to different processors, and provide functions that help programmers write software. Computers that use disk memory-storage systems are said to have disk operating systems (DOS). MS-DOS is the most popular microcomputer operating system. UNIX, a powerful operating system for larger computers, allows many users and many different programs to gain access to a computer's processor at the same time. Visual operating systems called GUIs (graphical user interfaces) were designed to be easy to use, yet to give UNIX-like power and flexibility to home and small-business users. Future operating systems will enable users to control all aspects of the computer's hardware and software simply by moving and manipulating their corresponding "objects," or graphical icons displayed on the screen. Sometimes programs other than the operating system are built into the hardware, as is the case in dedicated computers or ROM chips. Most often, however, programs exist independently of the computer. When such software is loaded into a general-purpose computer, itautomatically programs the computer to perform a specific t...
