The Operating System | Computer for GCSE/IGCSE - Year 11 PDF Download

What does the Operating System do? 

File Manager

• The file manager is responsible for overseeing all types of files on a system, including text, graphic, and program files. It manages file permissions, such as viewing, opening, writing, and deleting files, aiming to organize and control files for user convenience. Additionally, it serves to safeguard users from inadvertent errors.

Handling Interrupts

• An interrupt serves as a signal from a device or software to the processor, causing it to temporarily halt its current operations. This pause allows the processor to address the incoming request promptly.
• Interrupts can manifest in various forms:
  • Software errors, such as encountering missing files or unresponsive software applications.
  • Users triggering actions like Ctrl+Alt+Delete to perform functions like locking the system or logging off.
  • Instances where copying files is halted because a file with the same name already exists in the destination folder.
• When an interrupt is received by the CPU, it can either continue or complete the desired action. 
• The status of the current task is saved to the interrupt service routine when an interrupt is initiated. 
• After the interruption is handled, the system resumes its normal operation seamlessly.

User Interface Importance

• Operating systems require users to engage via a user interface, which translates user inputs into computer-readable formats and vice versa.
• Numerous computer or database operating systems employ intricate programming languages that are not user-friendly.
• User interfaces are developed to simplify operating system control for users. An effective interface prioritizes ease of use.
• For example, uniform menu layouts and consistent operations, such as right-click functions, contribute to a user-friendly interface.

Managing Peripherals and Drivers

• The primary purpose is to manage all connected devices within the computer system, encompassing input devices like keyboards and mice, as well as output devices like monitors and printers.
• Communication with these devices occurs through software known as drivers, which translate instructions from the device manager into formats understandable by the devices. Peripherals such as mice, keyboards, and printers all require drivers for effective communication with software.

Memory Management

• Memory management oversees the Random Access Memory (RAM), which programs utilize extensively during operation. While some programs are large and intricate, utilizing RAM extensively, others are smaller and require less RAM.
• Memory management validates and allocates requests from programs, ensuring their legitimacy. It also deallocates space and transfers data to virtual memory when necessary, facilitating the simultaneous operation of multiple programs.

Multi-tasking Efficiency

• Multitasking enables concurrent execution of software tasks, ensuring simultaneous completion of multiple elements. It employs a system called time slicing, which divides different tasks into smaller segments.
• These tasks can be sequentially executed, providing the illusion of simultaneous completion, rather than waiting for one operation to finish before proceeding to the next task.

Application Program Interface (API)

• Application programs and hardware interact via an interface within the operating system known as an Application Programming Interface (API).
• This API acts as a library interface, facilitating data exchange between software components to enable processing.
• When an application is installed on the system, the operating system takes charge of this process. It allocates memory space, regulates access to the application's data and devices, and manages user access.

Ensuring System Security

System security pertains to safeguarding the operating system, ensuring vigilant monitoring and proactive measures to maintain its integrity. Key areas of focus include:

• User management, involving the creation and deletion of system users.
• Granting access level privileges, such as administrator rights for system modification or file access, contrasting with standard user rights for software and file utilization.
• Auditing, entailing the logging of file modifications, deletions, and creations.
• Defense against threats like viruses, worms, malware, and remote hacker intrusions.
• Regular security updates to rectify vulnerabilities in the operating system through patches.

Managing User Accounts

• Every user is assigned an account to access the system, receiving a username and required to establish a password adhering to preset rules.
• Accounts are then allocated varying access levels, tailored to individual requirements and security protocols. This includes monitoring login activity and implementing automatic logouts for inactive sessions.

Hardware, Firmware & the OS

• Application Software communicates with the operating system to interact with hardware.
• The hardware processes and transmits information to the operating system, which communicates back to application software in a loop.

Firmware

• Firmware plays a crucial role in ensuring hardware components function properly.
• When a computer boots up, it first looks into the ROM for initial boot-up instructions stored in a Bootstrap loader.
• The basic input/output system (BIOS), acting as firmware, manages this initial process, providing low-level control for all devices.
• After BIOS completes its tasks, the instructions are transferred to RAM for processing by the operating system.
• This additional layer ensures that hardware devices like keyboards are accessible and can directly communicate with the operating system.
• For instance, When typing on a word processing document, the software first communicates with the operating system to request key presses. It then checks with the firmware to ensure the availability of the keyboard. Once the connection with the hardware is confirmed, the software communicates directly with the keyboard through the firmware. Key instructions are then relayed back to the operating system and ultimately displayed on the word processing software.