What is Operating System(OS)?
OS is a class of program known as system software; it is a software that provides facilities that simplifies the operation of computer system and provides and environment for execution of other programs. other programs on the OS gain access to the computer system. In a simply term, Operating System manages the entire resources of a computer.
TYPES OF OPERATING SYSTEM
Single User Operating system: As the name/ implies, this OS is designed to manage the computer so that one user can effectively do one thing at a time i.e. the user assign the whole machine to himself e.g. MS DOS, PC DOS. The set back in this type of OS is that the CPU is poorly utilized, Memory management is poor because the whole memory is allocated to a single user, No competition for the use of I/O devices.
Batch Processing
In batch processing, a program loader was introduced to all for continuous series of job to be loaded automatically from input device. In this case the jobs are not processed until fully input. The jobs are entered and stored on a disk in a batch queue and run one or more at a time. In this system, user has to wait for days or hours to have their jobs executed. The problems here are that, A single error like comma will abort a job, Correction is done off line and when the job is resubmitted the user has to wait again for days or hours for another execution.
Multi Tasking Operating System.
This operating system allow multiple jobs in the min memory at once and the processor is switched from one job to another in order to keep several job executing while at the same time keeping the peripheral devices in use. This is made possible because some jobs are CPU limited and other are I/O (input/output) limited.
I/O limited jobs are jobs whose execution is dependent on peripherals. e.g. most database management system spent much time on the I/O operations.
CPU limited jobs or CPU bound. This operation takes more of the CPU time e.g. scientific calculations. The OS has to manage memory space by preventing one task or process being run into the memory space of another tasks.
Multiple processing Operating System
This types of OS manages computer with two or more CPUs. Therefore the OS divides the workload among CPUs. This OS support simultaneous execution of processors.
Real Time Operating System.
Real time Operating system manages the resources of the computer so that a particular operation executes in the exact amount of time. The primary concern of Real Time Operation System is to provide quick response to meet schedule. It is expected to process interrupts without missing any event. It is used to tackle external events like. Telephone switching, heart beat monitoring system etc.
Distributed Operating System
A distributed operating system is an autonomous computer system capable of communicating to one another via interconnection. The operating system that manage this computer is called distributed operating system. Distributed Operating system provides wide sharing of resources such as processors, file and I/O devices without being aware of where the service could be found. Another example of distributed operating system is Network OS.
Functions of Operating System
OS is the manager of all the computer resources. Some examples of computer resources are: Main Memory, Device Drivers, I/O devices, processor, Files, Processes and Communication devices.
Function
Memory Management: The OS must manage the allocation of memory to process and ensure that one process cannot run into the memory space of another process.
Virtual management: The OS is capable of transforming a raw memory into a virtual memory in the hard disc of a computer at run time for the economy of memory space in the main memory. i.e. The OS can provide a memory, other than the actual memory.
File Management: The OS manages a number of transactions on files. Such as file creation, file destruction, open, close and append.
- In file creation, the OS assign physical storage space and creates the directory entry.
- File destruction; OS can create a file so, OS can destroy a file from storage and release its space. So, the removal of a file from a storage and release its space is known as the file destruction.
- Open: is the command that tells the OS to locate a file and read the directory information.
- Close: Close informs the OS that the file is no longer needed.
- Append: Append operations tells the OS to add records to the end of an existing file.
Process Management:
The Operating System (OS) provides supervisory calls for managing processes and must manage the allocation of resources to a process.
Device Management: OS manages hardware devices that are not of the motherboard through drivers e.g. Drivers take data that the OS had defined as files and translates them into bits, which are placed in storage devices or a series of laser pulses in a printer.
OS Manage Input and Output:
Managing input and output is largely a matter of managing queues and buffers. Queues and buffers. Queues and buffers are special storage facilities that hold data in I/O operations for effective utilization of CPU. The need for buffer arises as a result of differences in the speed between the I/O Devices and the processor.
Provision of User Interface: OS provides structure to the interaction between a user and the computer. Some OS like MS windows, Linux provide graphical user interface.
Resources Sharing: OS has the facility that enables a set of people share a computer resources effectively. The OS allows user to share resources such as a processor, memory, and peripheral Devices, A resource is shared because it may be too expensive to dedicate a resource to a single user.
Scheduling: Is the allocation of processor time to the various jobs in such a way as to optimize the computer system performance.