Operating System (OS)

OS 

The operating system (OS) is defined as a set of software, which is the link between the user and the computer. It is also defined as the main operator of the computer and the coordinator between the hardware. software; That is, he is responsible for managing the computer; Where the operating system is considered as a translator or means of communication between the user and the computer. The operating system is defined as a set of basic programs that manage the computer, organize all the tasks that it performs, and make it easier for the user to benefit from the equipment and accessories that make up the device, as well as enable him to benefit from various application programs. Such as: word processing software, or mathematical business software The operating system can also be defined as the main program for any computer device; He is responsible for the operation of the device and the work of the rest of the programs properly; When the computer is turned on, the device copies the operating system files from the hard disk to the memory. So that the central processing unit (CPU) can execute device commands without having to know the details of the operations inside the computer, and the operating system requires programmers at the highest level to write, develop, and maintain it, and these programmers are called operating system programmers.

operating system tasks

The tasks of each operating system differ according to the type of computer; Large computers whose work requires connecting to other devices, or allowing more than one person to use them at the same time, need an operating system that helps them deal with computer units and peripherals. As for personal computers, their operating system is simpler; Because it deals with one user and simple operations Data path control: The operating system manages the flow and path of data. By controlling its transmission between computer units Controlling the input and output units: This is done by controlling the process of entering data into the computer through the input units, such as the keyboard or mouse, monitoring the processing operations, and then displaying the data on the output units such as the monitor or printer. Fault detection: The system runs special software when a specific malfunction occurs, which is concerned with fault detection and giving a report on the fault. Control of the main memory unit: Some operating systems have the ability to run more than one program at the same time, and some allow more than one user to work on the device at the same time. The role of the operating system here is to distribute the main memory to more than one user. If more than one user is connected to the account Communication with the user: The operating system is a means of communication between the computer and the user. It acts as a translator between the user and the computer; It helps the computer user to follow up on the software and commands that have been executed by displaying them on the command issuance screen. To direct the computer properly, and this is done by showing the user interfaces (User Interface). Downloading application software: Here lies the role of the operating system in transferring application software from the storage media to the main memory, and then to the central processing unit to be executed.

How operating systems work

The operating system follows a flow chart of operations; To carry out the tasks entrusted to him, and passes through several stages, which are: Operation: The operating system reads and executes the instructions stored in the Read Only Memory (ROM - Read Only Memory) when the computer is turned on.

. Check: The operating system checks input units and output units. to ensure its safety.

Loading the system: After ensuring the integrity of the input and output units, the operating system is loaded from the soft and hard disks.

Receiving orders: this is by taking orders from the computer user; to be executed by the operating system. Operation of the system: It is the most important stage. As the system starts executing the user's orders immediately after completing the download process and receiving the orders, and that is through the application software.

The end of the process and its repetition: at the last stage, the operating system returns to the first step, and remains waiting for new commands to be issued by the user, to start executing them in the same way again.

Types of operating systems

Operating systems according to the number of programs The operating system is divided in terms of its ability to run more than one program for the same user into two parts: Multi-tasking system: Here the user is allowed to deal with more than one program at the same time. Single-Tasking System: This system does not allow the user to run more than one program at the same time.

Operating systems according to the number of users: Operating systems are divided in terms of the number of users into two parts: MultiUser: It is the system that allows software to be run on a computer by more than one user at the same time. Single-User System: A system that does not allow more than one user to run the software on the computer at the same time. 
 

Operating systems according to the number of users and programs From the above, it is concluded that the types of operating systems are summarized as follows: Single-User-Single-Task System: Allows one user to work on the device; That is, one user and only one task at the same time, and this type is known as one of the weakest types of operating systems, and it was used in old computers, and an example of it (Ms-Dos). Single user-multitasking system: This type is common in personal computers. Where this system is used to execute a set of commands for one user, and one of its advantages is its ability to perform multiple tasks, and examples of it (Windows, Mac)

Multi-user system - single task: It provides the opportunity for users to work at the same time on the computer, but only one program is required for each of them; This is because it lacks the multi-execution feature, which is common on server computers.

Multi-user - multi-tasking: It is one of the most powerful systems, and is used in mainframe computers. It allows a group of users to work on the same computer together, and perform different tasks at the same time, allowing each user to deal with the computer as if they were using it alone.

 :Operating system version

Among the most important versions of the operating system:

Windows operating system:

Windows operating system (Windows) produced by Microsoft, which is one of the most common systems; Because of its ease of use and learning; This is due to its dependence on the graphical user interface (Graphical User Interface), and its versions (windows 95 xp, windows 98, window)

 DOS operating system:

Disk Operating System - DOS means the disk operating system, and it is a single-function system for operating the personal computer, and it is considered one of the first generation operating systems, back in 1981 AD, and it is produced by (IBM), and it was developed by Microsoft to produce a version (MS- Dos), and it is mentioned that this system is compatible with (INTEL) processor.

Macintosh operating system:

Macintosh operating system (MAC) from Apple Macintosh, the first company to use graphical interfaces in 1984 AD, and developed the operating system until the Macintosh became in most devices that use texts and edit files; This is due to the ease of dealing with the system, and the system is suitable for commonly used applications, provides the Arabic language, and allows for multitasking, and despite the advantages and ease of use of these devices, they are less widespread than the devices compatible with the personal computer (IBM).

Unix operating system:

The UNIX operating system was established by AT&T in 1969, and developed in 1973. It is used to operate server computers, and it is worth noting that it can be used with all types of computers. Because of the ease of writing commands, running its applications and programs, and its multitasking, and among its advantages is the protection of documents from viewing them, and the possibility of making its versions on all types of computers. This system has two methods of dealing: the linear interface method, and the graphical interface method. Among the systems produced by the Unix system is the Linux system .

The operating system call feature

The operating system call feature is defined as a way to interact with the computer by requesting a service from the operating system on which it is running. Call the system in assembly language or a high-level language like (C) or (Pascal), and there are many situations in which you need to call the operating system, such as; A request to create a file, delete it, read or write a file, in addition to accessing devices connected to the computer, such as a printer, scanner, etc.