Basic Functions of Os - Free Essay Example

Sample details Pages: 4 Words: 1199 Downloads: 3 Date added: 2017/09/13 Category Advertising Essay Did you like this example? Thus the basic functions of an OS are – 1. Process Management – Managing the programs that are running. 2. Memory Management – Managing and rationing the memory between processes and data. 3. Storage Management – Managing the permanent Storage of data on disks or other media 4. I/O Management – Managing the input and output 5. Device / Resource Management – Managing devices and resources and allowing the users to share the resources 6. Security and Protection – Securing the system against possible unauthorized access to data or any other entity. Protecting the parts of the system against damage. 7. Booting the System and getting it ready to work. 8. Data communications – Providing interface to connect to other computers or allowing others to connect Definition: An operating system is a collection of software that coordinates the working of the different components of the system and gets the user’s job done. The operating system provides the user with all the basic things necessary to do his job. What does an os do An Operating System exploits the hardware resources of one or more processors to provide a set of services to system users. * An Operating System also manages secondary memory and input/output devices on behalf of its users. Process Control Block: A data structure by which the system identifies a process. It contains * Identifier: A unique integer associated with a process * State : A currently executing process is in running state * Priority : Priority level relative to other processes * Program cou nter : Address of the next instruction of the program to be executed. Memory pointers: pointers to the program code and data associated with the process, and any shared memory blocks * Context data: Data in the registers in the processor during process execution. * I/O status information: outstanding I/O requests, I/O devices allocated to the process, a list of files is use by the process, etc. * Accounting information: amount of processor time, etc. Directry structure of unix: The FreeBSD directory hierarchy is fundamental to obtaining an overall understanding of the system. The most important concept to grasp is that of the root directory, â€Å"/†. Don’t waste time! Our writers will create an original "Basic Functions of Os" essay for you Create order This directory is the first one mounted at boot time and it contains the base system necessary to prepare the operating system for multi-user operation. The root directory also contains mount points for other file systems that are mounted during the transition to multi-user operation. A mount point is a directory where additional file systems can be grafted onto a parent file system (usually the root file system). This is further described in  Section 3. 5. Standard mount points include  /usr,  /var,  /tmp,  /mnt, and  /cdrom. These directories are usually referenced to entries in the file  /etc/fstab. etc/fstab  is a table of various file systems and mount points for reference by the system. Most of the file systems in  /etc/fstab  are mounted automatically at boot time from the script  rc(8)unless they contain the  noauto  option. Details can be found in  Section 3. 6. 1. A complete description of the file system hierarchy is available in  hier(7). For now, a brief overview of the most common directories will suffice. Directory| Description| /| Root directory of the file system. | /bin/| User utilities fundamental to both single-user and multi-user environments. /boot/| Programs and configuration files used during operating system bootstrap. | /boot/defaults/| Default bootstrapping configuration files; see  loader. conf(5). | /dev/| Device nodes; see  intro(4). | /etc/| System configuration files and scripts. | /etc/defaults/| Default system configuration files; see  rc(8). | /etc/mail/| Configuration files for mail transport agents such as  sendmail(8). | /etc/namedb/| named  configuration files; see  named(8). | /etc/periodic/| Scripts that are run daily, weekly, and monthly, via  cron(8); see  periodic(8). | /etc/ppp/| ppp  configuration files; ee  ppp(8). | /mnt/| Empty directory commonly used by system administrators as a temporary mount point. | /proc/| Process file system; see  procfs(5),  mount_pro cfs(8). | /rescue/| Statically linked programs for emergency recovery; see  rescue(8). | /root/| Home directory for the  root  account. | /sbin/| System programs and administration utilities fundamental to both single-user and multi-user environments. | /tmp/| Temporary files. The contents of  /tmp  are usually NOT preserved across a system reboot. A memory-based file system is often mounted at/tmp. This can be automated using the tmpmfs-related variables of  rc. conf(5)  (or with an entry in  /etc/fstab; see  mdmfs(8)). | /usr/| The majority of user utilities and applications. | /usr/bin/| Common utilities, programming tools, and applications. | /usr/include/| Standard C include files. | /usr/lib/| Archive libraries. | /usr/libdata/| Miscellaneous utility data files. | /usr/libexec/| System daemons system utilities (executed by other programs). | /usr/local/| Local executables, libraries, etc. Also used as the default destination for the FreeBSD ports framework. Within  /usr/local, the general layout sketched out by  hier(7)  for  /usr  should be used. Exceptions are the man directory, which is directly under  /usr/local  rather than under  /usr/local/share, and the ports documentation is in  share/doc/port. | /usr/obj/| Architecture-specific target tree produced by building the  /usr/src  tree. | /usr/ports/| The FreeBSD Ports Collection (optional). | /usr/sbin/| System daemons system utilities (executed by users). | /usr/share/| Architecture-independent files. | /usr/src/| BSD and/or local source files. | usr/X11R6/| X11R6 distribution executables, libraries, etc (optional). | /var/| Multi-purpose log, temporary, transient, and spool files. A memory-based file system is sometimes mounted at  /var. This can be automated using the varmfs-related variables of  rc. conf(5)  (or with an entry in  /etc/fstab; see  mdmfs(8)). | /var/log/| Miscellaneous system log files. | /var/mail/| User mailbox files. | /var/spo ol/| Miscellaneous printer and mail system spooling directories. | /var/tmp/| Temporary files. The files are usually preserved across a system reboot, unless  /var  is a memory-based file system. /var/yp/| NIS maps. | Functions of an OS: The operating system on your computer has many functions. While you may not be aware of what many of them are or actually do, the operating system helps you navigate your computer more easily and allows you to manage programs and functions with the computer system itself. One function of your operating system is process management. Every program running on a computer – whether it is in the background or the foreground – is a process. Generally, only one process per CPU can run at one time. However, multiple processes can run through multi-tasking which entails switching processes very quickly. The operating system makes this type of multi-tasking possible. A second function of the operating system is memory management. Computer memory is arranged in a hierarchical manner with the fastest registers first followed by the CPU cache, random access memory, and then disk storage. The operating systems memory manager coordinates the use of these various types of memory by tracking which one is available, which is to be allocated or de-allocated and how to move data between them. This activity, usually referred to as virtual memory management, increases the amount of memory available for each process by making the disk storage seem like main memory. Security is an issue that is very important to all computer users. The security function of your operating system is also very important to the programmers. The system will often use an allow/disallow protocol when other systems are trying to access resources on your computer. Still others will require the use of a user name and password to keep your system secure.