Operating System Fundamentals

Operating System Basics

• Operating systems serve as an interface between users and computer hardware.
• Recommended books for studying operating systems include "Galin" and "Tanenbaum".
• Software consists of tested programs and documentation (user manuals).
• Software can be categorized into application software and system software.
• Application software is designed for specific tasks (e.g., VLC, MS Office).
• System software operates computer hardware and provides a platform for application software.
• Operating systems are classified as system software.
• System software examples include Linkers, loaders, and debuggers.
• Users interact with application software, which relies on system software to interact with hardware.
• Interfaces simplify hardware access, as demonstrated by a light switch example.

User Interaction and Resource Management

• Without an operating system, users would need to write complete programs to access hardware.
• Operating systems enable users to specify actions, handling background details.
• Operating systems manage hardware access, preventing conflicts between users.
• Operating systems act as an authority, allocating hardware to users as needed.
• Operating systems are resource managers or allocators, managing resources like CPU, memory, and I/O devices.
• Operating systems allocate resources to different processes or users.
• Operating systems manage CPU allocation through processor management or process management.
• Process scheduling is employed to determine which process gets CPU time.

Memory and I/O Management

• Memory management, primarily concerned with RAM (main memory), is a core OS function.
• Programs must be allocated space in main memory to execute.
• When programs are executed, they become processes, requiring main memory allocation.
• Operating systems determine which processes reside in main memory and for how long.
• Operating systems handle swapping processes between main memory and secondary storage.
• I/O device management involves managing devices like keyboards, mice, printers, and scanners.
• Operating systems manage access to I/O devices, ensuring that only one user accesses a printer at a time.

Storage and Security in Operating Systems

• Storage management pertains to the hard disk or secondary memory and how data is stored.
• Operating systems use file systems (NTFS, FAT) to manage data storage in directories, subdirectories, and files.
• File systems determine how data is stored and accessed on secondary memory.
• Security in operating systems involves protecting the system from unauthorized access.
• Operating systems manage user passwords and verify them for system access.
• Operating systems ensure the password entered matches the saved password.
• Security is enforced at the process level, preventing processes from interfering with each other.
• Each process operates in its own working space (PCB), isolated from others, handled by the OS.

Goals and Interface Types

• Operating systems have two key goals: convenience and efficiency.
• Convenience emphasizes ease of use and user-friendliness.
• The widespread adoption of Windows OS was due to its user convenience.
• Efficiency is a primary goal for supercomputers and mainframes, often operated by experts.
• User-friendliness is more important to average users, while experts value efficiency.
• Two main types of interfaces: GUI (graphical user interface) and CUI (character user interface).
• GUIs use images and icons for interaction, while CUIs require command-line input.
• System calls and system commands represent alternative interface types.
• DOS (Disk Operating System) is an example of a command-line-based system, while modern Windows uses a GUI.