9_pdfsam_1 - command shells : • Programs that direct the...

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An interface between the user and the hardware An environment for developing, selecting, and executing software. The operating system is the most important part of the systems software, managing the computer resources, including: The individual user sessions on multiuser computer systems. The division of CPU time across various tasks. The random access memory , or RAM, where both instructions and data are stored. The secondary storage systems, such as disk drives, CD-ROM drives, tape drives, or any other device in which information is stored in binary form on some medium. Information in secondary storage is organized into units called fles . When a computer is turned on, it loads the operating system into RAM (usually from secondary storage) before a user can execute a program. The system software may also include one or more
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Unformatted text preview: command shells : • Programs that direct the interaction with users. In most cases, when a you type a command, you are interfacing with the shell. • Early shells provided a “text” only interface, but modern computers (particularly personal computers) have graphical user interFaces (GUIs) that allow users to express what they want to do by using a pointing device and selecting among choices displayed on the screen. System software also includes: • Language compilers • Text editors • Utilities for Fle management • Utilities for printing Computer Languages Computer languages are used to develop programs to be executed. The can be described in terms of levels. Machine language: • Lowest-level language • Binary-encoded instructions that are directly executed by the hardware. 9...
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