Lesson 5: Introduction to Operating Systems
Chapter 5 study guide: quick notes, multiple-choice check, and short written answers.
1. Quick notes
Annotate and print
Use the tool bar at the bottom of the screen to highlight text, draw, and add sticky notes or text on top of these notes. Then save a PDF with or without your marks.
In the print window, choose "Save as PDF" as the destination. Chrome or Edge gives the best result.
Computer System Components
A computer system can be divided into four main components:
- Hardware: Provides basic computing resources (CPU, Memory, HDD).
- Operating System (OS): Software that controls and coordinates hardware use among apps and users.
- Application Programs: Software that utilizes resources to perform specific tasks (Word, Games).
- Users: The entities interacting with the computer.
The Role of the OS
The Operating System acts as an intermediary between the user and the hardware. It makes controlling the hardware friendly for the user.
Operating System Functions
The OS offers many core functions to help manage and run the computer:
- File Management: Manages how files are saved, organized, copied, and protected on storage drives.
- Device Management: Controls and coordinates hardware devices (Wi-Fi, printers, Bluetooth, monitors). Ensures fair allocation among applications.
- Security: Sets security rules, permissions, and access controls for the computer and apps.
- Networking Management: Oversees the interaction between the computer and network, ensuring secure data exchange and resource sharing.
- Process Management: Handles running programs, ensures fair allocation of CPU time, and avoids conflicts.
- Memory Management: Handles allocation and deallocation of RAM to running programs.
Process & Thread
- Process: An instance of a program being executed. Every time you open an app (or a new Chrome tab), a unique Process ID (PID) is created, and resources are allocated.
- Thread: The smallest unit of execution within a process. A single process can have multiple threads (multithreading) running simultaneously (e.g., in Word: typing, auto-saving, spell check).
- Multitasking: A single-core CPU does not run tasks simultaneously; it switches between them very rapidly. Multi-core CPUs can truly handle tasks simultaneously.
Process States
A process goes through different states:
- New: Being created and set up.
- Ready: Waiting to be assigned CPU time.
- Running: Currently executing on the CPU.
- Waiting: Waiting for I/O or other events (like a printer to finish).
- Terminated: Completed execution.
Memory Management & Allocation
Every spot in the RAM has a Physical Address known only to the OS and hardware. When a program runs, the OS assigns it a Logical (Virtual) Address. The OS translates logical to physical addresses, ensuring a program only accesses its own memory zone.
- Static Allocation: Fixed size assigned before running. Fast but not flexible.
- Dynamic Allocation: Assigned while running, can grow or shrink. Flexible but slightly slower.
Virtual Memory & Swapping: If RAM is full, the OS uses part of the hard disk as extra "Virtual Memory". Active apps stay in RAM, while inactive apps are "swapped" to the disk. This slows performance but prevents crashing.
Memory Hierarchy
OS Types
- GUI (Graphical User Interface): Uses visual presentations (icons, menus, mouse). E.g., Windows, macOS, Android.
- CLI (Command-Line Interface): Text-based interface relying on typed commands. E.g., Linux, UNIX.
Updates vs. Upgrades
- OS Update: Small software fix (patch) for bugs or security. Cumulative updates include all previous patches.
- OS Upgrade: A entirely new version of an OS with significant improvements (e.g., Windows 10 to Windows 11).
Architecture & Server OS
- 32-bit vs 64-bit: Older 32-bit CPUs address less memory (max 4GB RAM). Newer 64-bit CPUs handle significantly more data/memory. A 64-bit OS can run both 64-bit and 32-bit apps, but a 32-bit OS cannot run 64-bit apps.
- Server OS: Specialized OS (like Windows Server or Linux/UNIX) designed for multi-user, mission-critical, stable, and secure environments.
2. Multiple-choice check
Pick an answer to see right or wrong straight away, with a short explanation.
3. Short written questions
Try to answer in your own words first, then open the model answer.