In this chapter, you will learn about the general structure of functionalities and properties that the operating system provides for a typical computer system. A computer system may be organized in a number of different ways, which you can categorize roughly according to the number of general-purpose processors used.
You will learn about these properties one by one given below:
Single Processor Systems
Most systems at least contain a single processor. The variation of single-processor systems may be unexpected, but since these systems can range from PDA's to mainframe computers. On a single-processor system, there is one main CPU able to execute a general-purpose instruction layout, including different instructions from users and then process them. Almost every system has special-purpose processors within them. They may come in the appearance of device-specific processors, such as disks, keyboards, graphics controllers, etc.; or on mainframes, they may come in the form of more general-purpose processors.
Batch Processing
Batch processing is a method where an operating system gathers different programs along with the data together in a batch before starting the process. An operating system does the below-mentioned activities to perform batch related processing:
- The operating system identifies a job or sets of jobs that are further assigned to a sequence of commands, programs, and data within a single unit.
- The operating system maintains the lists of number jobs in memory. It then executes them one by one based on some scheduling algorithm.
- Most of the jobs In operating system are processed in the order they have been submitted, i.e., first come first serve [FCFS] manner.
Multiprogramming Property of Operating System
Multi-programmed structure or mechanism provides an environment where a variety of system resources like memory, CPU, and various peripheral devices gets utilized efficiently, but they do not offer for user interaction with the computer system. Time-sharing which is also called multitasking is a logical extension or enhancement of the term multiprogramming.
In time-sharing systems, the processor is given multiple tasks by switching among them, but the switches take place so frequently that the users can work together with each and every program while it is running and it seems that all of the programs are running simultaneously. Time-sharing needs an interactive computer structure that allows direct communication between the user and the system.
Multiprogramming in Operating System
A single user cannot keep either the processor or the Input / Output devices busy every time. The concept of multiprogramming is implemented to amplify CPU utilization by managing jobs so that the CPU always has at least one job to execute.
Sharing the processor, when multiple programs reside in memory at a single time, is termed as multi-programming. Multi-programming takes for granted a single shared processor for one or more tasks.
Clustered Systems in OS
Another type of multiple - CPU concept is the clustered structured system. Like multi-processing, clustered systems collect together several CPUs to achieve the better computational job. Clustered systems vary from multiprocessor systems, but in the same time, they are composed of two or multiple individual systems that are coupled as a single unit.
There are various important tasks that operating system handle, these tasks are called as operating system properties. It is a technique in which operating system collects a programs and data together in a batch before starting the execution or processing. In this system operating system defines a job with predefined sequence of commands, data and program as a single unit. Without any manual information operating system executes several jobs because operating system keeps various numbers of jobs in memory. The processing of jobs depends on
the sequence in which they are submitted like first come first serve. The memory is released when the execution of a job is completed and job’s output gets copied into an output spool for later printing process. Multiple tasks are executed simultaneously by CPU; they are done by switching the processes between them. In this case switching arises so frequently that the users can interact with each program while it is running.
In multitasking user directly gives the instruction to the program or operating system and gets an instantaneous response. This system is also known as time sharing system. Each and every user can have at least one separate job in memory.Batch Processing
Multitasking
Multiprogramming
Sharing the processor in case when there are two or more processes resides in memory is called as multiprogramming. Multiprogramming is used to increase the proper utilization of CPU by organizing the jobs in such a manner that CPU always has one to execute. In multiprogramming it is assumes that a single shared processor. Operating system keeps a set of several jobs in memory. CPU executes one job at a time which is loaded from main memory. In this system operating system monitors all the state of system resources and active programs using memory management programs to make sure that the CPU is never idle except there are no job.
Interactivity
Interactivity is simply defined as the user is capable to interact with computer system. An interface is provided by operating system to interact with system. Operating system manages input and output devices. There must be very short response time.
Real Time System
Usually dedicated embedded systems are represented as real time system. In this system operating system reads from and react to the sensor data. It must assurance response to events with fixed period of time to make sure the correct performance.
Distributive Environment
Multiple independed processors or CPUs in a computer system are referred as distributive environment. Operating system distributes computation logics among different physical processors. Each processor has its own local memory rather than sharing the memory or clock. Communication between processors are managed by operating system.
Spooling
It denotes to pushing data of various I/O jobs in buffer. It is basically simultaneous peripheral operation on line. In this process operating system handles I/O device data spooling as device have diverse data access rate. Operating system maintains the spooling buffer.
Operating System Services
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