1-1 ORGANIZATION OF COMPUTER SYSTEM COMPONENTS

    Now that we've examined what is a computer^[1], let's look again at our computer definition: A computer is a fast and accurate symbol manipulating system that is organized to accept, store, and process data and produce output results under the direction of a stored program of instructions. This section explains why a computer is a system and how a computer system is organized.
    Fig.1-1 shows the basic organization of a computer system. Key elements in this system include input, processing, and output devices. Let's examine each component of the system in more detail.
    INPUT DEVICES. Computer systems use many devices for input purpose. As shown in Fig.1-2, some INPUT DEVICES allow direct human/machine communication, while some first require data to be recorded on an input medium such as a magnetizable material^[2]. Devices that read data magnetically recorded on specially coated plastic tapes or flexible or floppy plastic disks are popular^[3]. The keyboard of a workstation connected directly to … or ONLINE to … a computer is an example of a direct input device^[4]. Additional direct input devices include the mouse, input pen, touch screen, and microphone. Regardless of the type of device used, all are components for interpretation and communication between people and computer systems.
    CENTRAL PROCESSING UNIT. The heart of any computer system is the central processing unit (CPU). As Fig. 1-3 shows, there are three main sections found in the CPU of a typical personal computer system: The primary storage section, The arithmetic-logic section, and The control section. But these three sections aren't unique to personal computer: They are found in CPUs of all sizes.
    OUTPUT DEVICES. Like input units, output devices are instruments of interpretation and communication between humans and computer systems of all sizes. These devices take output results from the CPU in machine-coded form and convert them into a form that can be used (a) by people (e.g. a printed and/or displayed report) or (b) as machine input in another processing cycle.
    In personal computer systems (Fig. 1-3), display screen and desktop printers are popular output devices. Larger and faster printers, many online workstations, and magnetic tape drives are commonly found in larger systems.
    The input/output and secondary storage units shown in Fig. 1-3 are sometimes called peripheral devices (or just peripherals). This terminology refers to the fact that although these devices are not a part of the CPU, they are often located near it.