SYSTEM SOFTWARE Prepared by: Mrs. Careene McCallum-Rodney

INTRODUCTION ______________________________________ There are 2 types of software : System Software Application Software What is the major purpose of each type of software ? Application software is designed to help people perform a certain type of work. System software is any software required to support the production or execution of application programs but which is not specific to any particular application.

Name the 2 main types of system software

Types of SYSTEM SOFTWARE Operating System Utility Programs

What are the functions of the O/S?

OPERATING SYSTEM ______________________________________ An Operating System (commonly abbreviated OS and O/S) is the software component of a computer system that is responsible for the management and coordination of activities and the sharing of the limited resources of the computer. An operating system is a program designed to run other programs on a computer. Operating systems are responsible for everything from the control and allocation of memory to recognizing input from external devices and transmitting output to computer displays.

FUNCTIONS OF O/S ______________________________________ PROCESS Management MEMORY Management FILE Management DEVICE Management SECURITY NETWORK USER INTERFACE

P ROCESS M ANAGEMENT ______________________________________ NOTE: A process is the unit of work in a system. The creation and deletion of both user and system processes The suspension and resumption of processes The provision of mechanisms for process synchronization The provision of mechanisms for process communication The provision of mechanisms for deadlock handling (deadlock is a situation in which each process in a set of processes is waiting for an event that only another process in the set can cause. since all the process are waiting, the system enters a deadlocked condition

M EMORY M ANAGEMENT ____________________________________ Keep track of which parts of memory are currently being used and by whom. Decide which processes are to be loaded into memory when memory space becomes available. Allocate and de-allocate memory space as needed.

F ILE M ANAGEMENT _________________________________ Creation and Deletion of files Creation and Deletion of directories Support of primitives for manipulating files and directories Mapping of files to secondary storage Backup of files on stable (non-volatile) storage media.

D EVICE M ANAGEMENT ______________________________________ A program, as it is running, may need additional resources to proceed. Additional resources may be more memory, tape drives, access to files, and so on. If the resources are available, they can be granted, and control can be returned to the user program; otherwise, the program will have to wait until sufficient resources are available. Files can be thought of as abstract or virtual devices. Thus, many of the system calls for files are also needed for devices. If there are many multiple users of the system, we must first request the device, to ensure exclusive use of it. After we are finished with the device, we must release it. Once the device has been requested (and allocated to us), we can read, write, and (possibly) reposition the device.

S ECURITY _________________________________ Security at the Operating System level is implemented at several levels ranging from password for access to the system to the isolation of concurrent processes running on the system. The file system also provides some degree of protection. The areas of security to be focused on are: Authentication using User IDs, Passwords, and Lock-words Access control list File Encryption File compression Activity logs

N ETWORK _______________________________ In a network operating system, the users are aware of the multiplicity of machines, and need to access these resources (meaning both hardware and software) by either logging into the appropriate remote machine, or transferring data from the remote machine to their own machine.

U SER I NTERFACE ________________________________ This is the portion of software that defines how a user interacts with a computer, including how the user enters data and instructions and how information is displayed on screen. This is a mediator between the user and the computer. User Interfaces provides a means of: Input - allowing the users to manipulate a system Output - allowing the system to indicate the effects of the users' manipulation

Command Line Interface Menu Driven Interface Graphical User Interface The OS is responsible for the interface displayed to users. An interface can be: U SER I NTERFACE ________________________________

COMMAND LINE VS GUI ______________________________________

C LASSIFICATION OF OS __________________________________________ Multi-user: Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users. Multiprocessing: Supports running a program on more than one CPU. Multitasking: Allows more than one program to run concurrently. Multithreading: Allows different parts of a single program to run concurrently. Real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.

Types of SYSTEM SOFTWARE Operating System Utility Programs

UTILITY SOFTWARE ______________________________________ These are software that help the user to do some tasks that are not provided by the Operating System. Now days, they usually come with the Operating System but they are developed by different companies. Functions of utility software. When your data has been destroyed in any way, you can recover and restore the data by using data recovery utility software. Anti-virus software are also utility programs that can help protect your computer from dangerous viruses that can damage your system. Examples of those utilities are MacAfee anti-virus, Avira anti-virus, web scan, Norton anti-virus, AVG, and so on.

UTILITY SOFTWARE ( CONT ) ______________________________________ Functions (cont): We also have back-up utility software that can help back up you data so that incase your hard disk damages, you can still have your data back. An example of this utility is Colorado scheduler. Sometimes your data can take up a lot of space on your hard disk and leave a very less space available. You can use a data compression utility to compress your data and create more space on your hard disk. An example of this utility is pk zip. Sometimes, files can also be scattered in bits on your hard disk and therefore making it difficult to access them. You can therefore defragment those files by running a disk defragmenter utility. The utility usually brings the files together and arranges them in an adjacent manner therefore making it easier to access the files.