Subject:Software. Operating Systems.
Questions:
Software.Types of software, targets and characteristics.
Basic concepts of OS. The evolution of operating systems.
Classification of operating systems, including for mobile devices.
Classification of desktop applications.
Modern general-purpose computers, including personal computers and mainframes, have an operating system to run other programs, such as application software. Examples of operating systems for personal computers include Microsoft Windows, Mac OS (and Darwin), Unix, and Linux.
The lowest level of any operating system is its kernel. This is the first layer of software loaded into memory when a system boots or starts up. The kernel provides access to various common core services to all other system and application programs. These services include, but are not limited to: disk access, memory management, task scheduling, and access to other hardware devices.
As well as the kernel, an operating system is often distributed with tools for programs to display and manage a graphical user interface (although Windows and the Macintosh have these tools built into the operating system), as well as utility programs for tasks such as managing files and configuring the operating system. They are also often distributed with application software that does not relate directly to the operating system's core function, but which the operating system
distributor finds advantageous to supply with the operating system.
Operating systems are used on most, but not all, computer systems. The simplest computers, including the smallest embedded systems and many of the first computers did not have operating systems. Instead, they relied on the application programs to manage the minimal hardware themselves, perhaps with the aid of libraries developed for the purpose.
Definition of Operating System
An operating system (OS) is a software program that manages the hardware and software resources of a computer. The OS performs basic tasks, such as controlling and allocating memory, prioritizing the processing of instructions, controlling input and output devices, facilitating networking, and managing files.
In other word, OS is the most important program that runs on your computer. It manages all other programs on the machine. Every PC has to have one to run other applications or programs. It’s the first thing “loaded”.
OS performs basic tasks, such as:
· Recognizing input from the keyboard or mouse;
· Sending output to the monitor;
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· Keeping track of files and directories on the disk
· Controlling peripheral devices such as disk drives and printers.
Classification of operating systems.Types of operating systems.
Generally, there are four types, based on the type of computer they control and the sort of applications they support.
Single-user, single task
This type manages the computer so that one user can effectively do one thing at a time. This type of operating system is specifically designed to run this one application efficiently for that one user. An example of this would be a mobile phone (not smart phone) where there is only going to be a running one application at any given time whilst they use the phone. An example of an OS that is single user single process is the OS know as Palm OS which was used on mobile phones and PDAs.
Multi-user, multi-task
Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users. An example is a Unix server where multiple remote users have access (such as via Secure Shell) to the Unix shell prompt at the same time. Another example uses multiple X Window sessions spread across multiple terminals powered by a single machine - this is an example of the use of thin client. Similar functions were also available under MP/M, Concurrent DOS, Multiuser DOS and FlexOS.
Real Time Operating Systems (RTOS)
A real-time operating system is an operating system that guarantees to process events or data by a specific moment in time.
A real-time operating system may be single- or multi-tasking, but when multitasking, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.
RTOS are used to control machinery, scientific instruments, and industrial systems. There is typically very little userinterface capability. Resources are managed so that a particular operation executes precisely the same every time.
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Single-user, Multi-tasking
A single-user multitasking operating system is an operating system that allows a single user to simultaneously run multiple applications on a computer.
This is the type of operating system most desktops and laptops use today. Microsoft’s Windows and Apple’s MacOS are both examples of operating systems that will let a single user have several programs in operation at the same time.
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