Functions of Operating Systems V1.0 (22/10/2005)

software Computer cannot operate solely depend on hardware Must use software to “drive” the hardware Software can be categorized as application software and system software

Application software Software decided to help users finish real- world jobs are called application software

System software prerequisite for a computer to operate Commonly known as software that helps computers to run includes tiny programs; each functions differently Control operation of computer system and aid computer / other programs through collaboration between programs Directly control, manage and coordinate hardware Classified as utility program, device driver and operating system

Utility Program Tiny programs with different functions Help users finish specific tasks at low-level Tasks include managing computer, devices and programs Help in tasks that cannot be completed by operating system OR some “powered” features of OS

device driver Protocol between operating system and hardware Aid operating system core to control hardware, provide hardware status, and complete the actual I/O operations Every device should bear with a specific device driver After adding hardware or re-installing operating system, all device drivers should be re-installed Without appropriate driver, the hardware could not operate Modern operating systems already bundled a device driver database After hardware installation (maybe after reboot), OS will install the driver automatically If appropriate driver is found, it will be installed If not found, require manually install the proper driver To fully utilize function and characteristics of hardware, you should use drivers originated from manufacturer

operating system System that composed of programs of different functions Functions and architecture increasing trend User interface between computer hardware and users Users through this to avoid low-level computer operations Controls all computer operations Ensures all components function effectively

Fundamental functions of operating systems : 1. Control Processing 2. Resource Management 3. File System Management 4. User Interface 5. Utility Programs 6. Security

1. Control Processing Execute software Process is every program, including its resources, that runs in the memory When jobs are scheduled in CPU, Process is the basic unit used Manage execution plan by allocating resources to difference processes

2. Resource Management Aid software drives hardware and fetch resources to complete tasks Monitor, control and coordinate all computer system resources, like memory, peripherals and storage devices Monitor hardware and control data I/O Provide proper management and coordinate the resources, optimize when resources allocation Effectively allocate memory for utility software and operating system Control memory modules and allocate memory addresses Ensure all processes have enough memory to run Prohibit memory allocated to one process being accessed by the other Effectively allocate I/O devices to different processes. According to process priority, allocate CPU,memory, and I/O devices When out of resource, allocate resource to higher priority processes

3. File System Management Organize and manage files stored in computer Format and copy disks List files for users to view Check available and used space on disk Copy, rename, delete, move and order Find lost files, restore corrupted files and backup

4. User Interface (UI) Provide UI between user/application software and hardware Users does not need to know operating system internals but must know how to use UI Before Windows, users use textual command to operate computer textual command requires users remember all commands Most modern operating systems use Graphical UI Use mouse to operate computer GUI is more humanistic than command prompt Use multimedia to make UI rich No more text commands No special training GUI aid development of computer a lot in last decade

5. Utility Program Different operating systems provide different utility programs Aid system maintenance and recovery Find root cause of problems

6. Security Register all programs Authenticate all users Maintain basic security Maintain and recover functional errors Error messages Provide fundamental information of processes

Layers in computer systems Users operate through application software in GUI Application software drive hardware through operating system Hardware must be called through driver from operating system Relation of User/application software and hardware is like onion: one wraps the other With the popularity of computer, users will maintain computers by themselves Thus, UI can directly run on operating system Some GUI can drive hardware directly through utility programs Some application software can drive hardware directly

User UI(by operating system) Application software operating system Utility Programs Basic I/O system drivers hardware System software