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Two Types of Software: 1. Application Software: Instructions to accomplish a specific task (ie. MS Word, Internet Explorer) 2. System Software: Set of programs that help run the computer. Operating Systems: Controls how computer system functions. Utility Programs: Small programs that perform many general housekeeping tasks. System Software: Operating Systems The operating system (OS) is the first thing loaded onto a computer. Without an operating system, a computer is useless. Most desktop or laptop PC’s that you buy come pre-loaded with Windows 8 (newest). Macintosh computers come pre-loaded with OS X Mavericks. Many corporate servers use the Linux or UNIX operating systems. The operating system on these computers is Windows7. The Operating System's tasks, in the most general sense, fall into five categories: Processor Management Memory and Storage Management Device Management Application Interface User Interface Processor Management The operating system schedules the processes (tasks that come from the applications) that will be executed by the CPU. With a multi-tasking system, the operating system must arrange the execution of processes so that you believe that there are several things happening at once. In order to give the appearance of lots of things happening at the same time, the operating system has to switch between different processes thousands of times a second. Trouble can come if the user tries to have too many processes functioning at the same time so computer freezes. This is called thrashing, and it usually requires user intervention to stop processes and bring order back to the system (CTRL+ALT+DEL and End Task). A dual core processor is a CPU with two separate cores in one physical processor, each with its own cache. It's the equivalent of getting two microprocessors in one. Eventually, we will have multi-processor systems. Memory & Storage Management The operating system must balance the needs of the various processes with the availability of the different types of memory. For example, moving information in RAM to hard disk can greatly expand RAM space at no cost. This technique is called virtual memory management. Ranked in order of speed (fastest-slowest) and storage (smallest to largest), the types of memory in a computer system are: High-speed cache - This is fast, relatively small amounts of memory that are available to the CPU through the fastest connections. Cache controllers predict which pieces of data the CPU will need next and pull it from main memory into high-speed cache to speed up system performance. Primary memory (or Main memory) - This is the RAM that you see measured in gigabytes when you buy a computer. Secondary memory - This is most often some sort of rotating magnetic storage (hard drive) that keeps applications and data available to be used, and serves as virtual RAM under the control of the operating system. Device Management The operating system manages the hardware and peripheral devices. One of the challenges facing developers is keeping their operating systems flexible enough to run hardware from the thousands of vendors manufacturing computer equipment. Today's systems can accommodate thousands of different printers, disk drives and special peripherals in any possible combination. A driver (special program for the hardware) is a translator between hardware and the operating system or application programs. One reason that drivers are separate from the operating system is so that new functions can be added to the driver without requiring the operating system itself to be modified, recompiled and redistributed. Plug and Play refers to hardware that you can just plug in and it runs (may need to install driver). Application Interface Application Program Interface (API) is a way for software to interact with other software and system resources. It uses blocks of code for similar procedures to prevent redundancy and make it easier for software developers. Our Application Interface is Windows7. User Interface User interface (UI) brings structure to the interaction between a user and the computer. Graphical user interface (GUI), sits as a layer above the operating system itself. Our User Interface is Windows7 (login screen). Reference: http://computer.howstuffworks.com/operating-system5.htm Utility Programs Appearance and Themes Network and Internet Connections Add or Remove Programs System Maintenance Printers and Other Hardware System Restore System Backup Task Scheduler Accessibility Options Security Options