LECTURE NOTE FOR BCA-Ist Year ---- Office Management Tools (BCA106) Introduction to Operating System The operating system (OS) is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs and applications. Computer operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as printers. For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop — it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system. An operating system (OS) is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. The other programs are called applications or application programs. The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface such as a command line or a graphical user interface (GUI). An operating system performs these services for applications: In a multitasking operating system where multiple programs can be running at the same time, the operating system determines which or that one is using the ``extended filesystem''.Office Management Tools (BCA106) applications should run in what order and how much time should be allowed for each application before giving another application a turn. It can offload the management of what are called batch jobs (for example. It sends messages to each application or interactive user (or to a system operator) about the status of operation and any errors that may have occurred. The difference between a disk or partition and the filesystem it contains is important. Most programs operate on a filesystem. It manages the sharing of internal memory among multiple applications. reasonably enough. A few programs (including. printers. It handles input and output to and from attached hardware devices. The word is also used to refer to a partition or disk that is used to store the files or the type of the filesystem. File Structure A File Structure should be according to a required format that the operating system can understand. that is. meaning the type of the filesystem. A filesystem is the methods and data structures that an operating system uses to keep track of files on a disk or partition. and dial-up ports. an operating system can manage how to divide the program so that it runs on more than one processor at a time. one might say ``I have two filesystems'' meaning one has two partitions on which one stores files. such as hard disks. the way the files are organized on the disk. programs that create filesystems) operate directly on the raw sectors of a disk or partition. On computers that can provide parallel processing.LECTURE NOTE FOR BCA-Ist Year ---. if there is an existing file system there it will be destroyed or seriously corrupted. Thus. printing) so that the initiating application is freed from this work. . and therefore won't work on a partition that doesn't contain one (or that contains one of the wrong type). Office Management Tools (BCA106) A file has a certain defined structure according to its type. . MS-DOS support minimum number of file structure. Unix.LECTURE NOTE FOR BCA-Ist Year ---. A source file is a sequence of procedures and functions. it also contains the code to support these file structure. When operating system defines different file structures. An object file is a sequence of bytes organized into blocks that are understandable by the machine. A text file is a sequence of characters organized into lines.