SYSTEM SOFTWAREPrepared 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

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

INTERFA

CE

PROCESS MANAGEMENT______________________________________

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

MEMORY MANAGEMENT____________________________________

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.

FILE MANAGEMENT_________________________________

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.

DEVICE MANAGEMENT______________________________________

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.

SECURITY_________________________________

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

NETWORK_______________________________

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.

USER INTERFACE________________________________

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

The OS is responsible for the interface displayed to users. An interface can be:

USER INTERFACE________________________________

COMMAND LINE VS GUI______________________________________

CLASSIFICATION 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.

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.