Chapter 6
Managing Hardware Assets
The modern computer system has six major components: a central processing unit, primary storage, input devices, output devices, secondary storage, and communications devices. Computers store and process information in the form of binary digits called bits. A string of eight bits called a byte. There are several coding schemes for arranging binary digits into characters. The most common are EBCDIC and ASCII. The CPU is the part of the computer where the manipulation of symbols, numbers, and letters occurs. The CPU has two components: an arithmetic-logic unit and a control unit. The arithmetic-logic unit performs arithmetic and logical operations on data, whereas the control unit controls and coordinates the computer's other components.
The CPU is closely tied to primary memory, or primary storage, which stores data and program instructions temporarily before and after processing. Several different kinds of semiconductor memory chips are used with primary storage: RAM is used for short-term storage of data and program instructions, whereas ROM permanently stores important program instructions. Computer processing power depends, in part, on the speed of microprocessors, which integrate the computer's logic and control on a single chip. Microprocessors' capabilities can be gauged by their word length, data bus width, and cycle speed. Most conventional computers process one instruction at time, but computers process one instruction at time, but computers with parallel processing can process multiple instructions simultaneously.
The principle forms of secondary storage are magnetic disk, optical disk, and magnetic tape. Magnetic disk permits direct access to specific records. Disk technology is used in on-line processing. Optical disks can store vast amounts of data compactly. CD-ROM disk systems can only be read from, but rewritable optical disk systems are becoming available. Tape stores records in sequence and only can be used in batch processing. The principal input devices are keyboards, computer mice, touch screens, magnetic ink, optical character recognition, pen-based instruments, digital scanners, sensors, and voice input. The principal output devices are video display terminals, printers, plotters, voice output devices, microfilm, and microfiche. In batch processing, transactions are accumulated and stored in a group until the time when it is efficient or necessary to process them. In on-line processing, the user enters transactions into a device that is directly connected to the computer system. The transactions are usually processed immediately.
