Operating System

Operating System

1. An operating system is a collection (or suite) of programs that manages and controls the computer.

   • Example operating systems include:
     • Microsoft Windows Apple OS X Linux Android IOS
   • Operating systems have many functions:
     • controlling hardware components
     • providing a platform for software to run on
     • providing a user interface
     • managing processes
     • managing the computer's memory
     • managing security
     • managing applications
     • managing input and output devices

2. User Interfaces

   • A user interface is a program, or suite of programs that allows a user to interact with a computer. There are three types of interface to be considered.
   • A graphical user interface is familiar to most users of PCs and laptops. GUIs feature a desktop where everything is displayed. Applications run in Windows, and all objects (apps, hardware and files) are represented by icons. Application features are accessible through the use of menus. Users interact with the interface by using a mouse and on-screen pointer.

3. Processor Management

   • Multitasking means to be able to run more than one program simultaneously. These programs perform processes. In the past, computers with CLIs were unable to multitask - the operating systems of the day only allowed one program to run at a time.
   • Multitasking is possible only if:
     • the operating system can support multitasking
     • the computer has enough memory to hold more than one program in primary memory at the same time

4. Memory Management

   • Computer memory must be managed to ensure that:
     • more than one program can run at the same time
     • more than one document can be opened at the same time
   • When a program is run, it is loaded into memory. The operating system determines how much memory the program requires, and allocates enough pages to hold it and its documents. When the program is closed, the allocated pages are freed up for use by other programs.

5. Input/output devices management

   • Input and output devices, which are also known as peripherals, are hardware devices connected to a computer, such as a screen, printer, keyboard or camera.
   • To operate a peripheral, the operating system uses a program called a device driver. Device drivers contain instructions on how to control a device. Each connected device has its own driver.
   • Using device drivers brings two advantages:
     • drivers can be updated, usually to give better performance or to remove a bug
     • any device can be used with the operating system, as long as a driver is available for it

6. Applications management

   • Application programs and hardware can communicate through an interface provided by the operating system. This is known as the application programs interface (API).

7. Security Management

   • Operating systems also manage security. They allow:
     • auditing (keeping a log) of files a user creates, accesses, edits and deletes
     • access levels to be given to users, such as administrator rights or standard user rights
     • individual users to be created and deleted

8. Hardware and software

   • Computer systems consist of hardware and software. Hardware is the physical components of the computer, such as the central processing unit (CPU), hard disk, monitor, keyboard and mouse. Software is the programs that run on a computer.