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Key Terms, Chapter 1: Overview, Flynn and McHoes, Understanding Operating Systems, Second Edition, PWS Publishing Co. (1997) Operating System: The software that manages all the resources of a computer system. Memory Manager: The section of the operating system responsible for controlling the use of memory. It checks the validity of each request for memory space and, if it's a legal request, allocates the amount needed to execute the job. Process Manager: A composite of two sub managers, the Job Scheduler and the Process Scheduler. It decides how to allocate the CPU, monitors whether it's executing a process or waiting, and controls job entry to ensure balanced use of resources. Device Manager: The section of the operating system responsible for controlling the use of devices. It monitors every device, channel, and control unit and chooses the most efficient way to allocate all of the system's devices. File Manager: The section of the operating system responsible for controlling the use of files. It tracks every file in the system including data files, assemblers, compilers, and application programs. By using predetermined access policies, it enforces access restrictions on each file. Main Memory: The memory unit that works directly with the CPU and in which the data and instructions must reside in order to be processed. Also called primary storage or internal memory. Central Processing Unit (CPU): The component with the circuitry, the "chips", to control the interpretation and execution of instructions. In essence, it controls the operation of the entire computer system. All storage references, data manipulations, and I/O operations are initiated or performed by the CPU. Hardware: The physical machine and its components, including main memory, I/O devices, I/O channels, direct access storage devices, and the central processing unit. Software: A collection of programs used to perform certain tasks. They fall into three main categories: operating system programs, compilers and assemblers, and application programs. Mainframe: The historical name given to a large computer system. It was characterized by its large size, high cost, and high performance. Minicomputer: A small to medium-sized computer system developed to meet the needs of smaller institutions. It was originally developed for sites with only a few dozen users. Microcomputer: A complete, small computer system, consisting of hardware and software, developed for single users in the late 1970s. Batch System: A type of system developed for the earliest computers that used punched cards or tape for input. Each job was entered by assembling the cards together into a "deck" and several jobs were grouped, or "batched", together before being sent through the card reader. Interactive System: A system that allows each user to interact directly with the operating system via commands entered from a keyboard. Also called time-sharing system. Read-Time System: An extremely fast computing system that's used in time-critical environments that require immediate decisions, such as navigation systems, rapid transit systems, and industrial control systems. Hybrid System: A computer system that supports both batch and interactive processes. It appears to be interactive because individual users can access the system via terminals and get fast responses, but it accepts and runs batch programs in the background when the interactive load is light. Multiprocessing: When two or more CPUs share the same main memory, most I/O devices, and the same control program routines. They service the same job stream and execute distinct processing programs concurrently. |
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