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LESSON 1: OPERATING SYSTEMS What is an Operating System? An Operating System (OS) is the software layer that connects computer hardware and applications. It controls hardware resources and provides a platform for applications. Key Functions An OS manages CPU scheduling, RAM allocation, file storage, security permissions, and input/output devices. Types of Operating Systems Batch OS: Executes similar jobs in grouped batches without real-time user interaction. Common uses include payroll and bank statements. Time-Sharing OS: Divides CPU time among multiple users to support interactive multitasking. Real-Time OS (RTOS): Provides strict, deterministic processing within required time limits. Used in airbags, heart monitors, and industrial robotics. Network OS (NOS): Uses central servers to manage network security, shared data, traffic, and peripherals. It provides access control, encrypted transmission, and centralized authorization. Networked & Distributed OS Distributed OS: Connects autonomous computers so they function as one system. Example: cloud clusters. Network OS: Runs on central servers to manage user security, shared data, network traffic, and peripherals across a local network. Key Security: Enforces access control, encrypted data transmission, and centralized user authorization across networks. Mobile vs. Desktop Platforms Mobile OS: Designed for touchscreens, wireless networks, and battery efficiency. Examples: Android and iOS. Desktop OS: Provides graphical interfaces and full multitasking. Examples: Windows, macOS, and Linux. Global OS Market Distribution Android – 41% Windows – 28% iOS – 17% macOS – 7% Linux/Other – 7% OS Evolution 1950s: Batch systems used punch cards and automated job processing. 1970s: Time-sharing and Unix introduced multi-user scheduling and interactive terminals. 1990s: GUIs and personal computing became widespread. 2000s onward: Mobile and cloud computing expanded, including Android and iOS. LESSON 2: COMPUTER SYSTEMS Computer System – A computer system is the combination of hardware, software, data, and liveware working together to process information. Four Core Components: Hardware: Physical components such as the CPU, RAM, motherboard, storage, and I/O devices. Software: Instructions that control hardware; includes system and application software. Data: Raw facts, numbers, and symbols processed into meaningful information. Liveware: People who operate, develop, maintain, and use computer systems. Hardware and Software Hardware: The physical components of a computer that perform tasks and run software. System Software: Operating systems (Windows, Linux) that manage hardware resources, system operations, and security. Application Software: Programs such as browsers and editors that help users perform specific tasks. Interdependence: Hardware needs software instructions to function, while software needs hardware to execute its instructions. Data and Liveware Data begins as raw facts and becomes meaningful information through processing. Liveware includes administrators, programmers, and end-users who manage systems, create programs, and use results. The Operational Lifecycle Continuous Data Transformation A computer system continuously captures, processes, stores, and outputs data. This four-step cycle is the foundation of all computing systems, from simple microcontrollers to large data centers. THE 4-STAGE WORKFLOW: Information Processing Cycle Input: Captures data and commands through keyboards, mice, sensors, and touchscreens. Processing: The CPU fetches, decodes, and executes instructions. Storage: Keeps active data in RAM and permanent files on SSDs or hard drives. Output: Presents processed results through monitors, printers, speakers, and other output devices. LESSON 3: ESSENTIAL COMPUTER SHORTCUTS Basic Shortcuts Ctrl + A: Select All. Ctrl + C: Copy. Ctrl + X: Cut. Ctrl + V: Paste. Ctrl + Z: Undo. Ctrl + Y: Redo. Ctrl + S: Save. Ctrl + P: Print. Ctrl + F: Find. Formatting & Text Navigation Ctrl + B: Bold or remove bold formatting. Ctrl + I: Italicize or remove italic formatting. Ctrl + U: Underline or remove underline formatting. Home: Move cursor to the beginning of the line. End: Move cursor to the end of the line. Ctrl + Home: Move cursor to the beginning of the document. Ctrl + End: Move cursor to the end of the document. Windows Navigation Shortcuts Alt + Tab: Switch between active applications. Alt + F4: Close the active application. Win + D: Show or hide the desktop. Win + L: Lock the computer. Ctrl + Shift + Esc: Open Task Manager. F2: Rename the selected file or folder. F5: Refresh the current window or page. Web Browser Navigation Ctrl + T: Open a new browser tab. Ctrl + W: Close the active browser tab. Ctrl + Tab: Switch to the next open browser tab. Ctrl + Shift + T: Reopen the last closed tab. Ctrl + D: Bookmark the current webpage. FOR REFERENCE/MORE KEYBOARD SHORTCUTS The General Shortcuts Ctrl + C: Copy. Ctrl + X: Cut. Ctrl + V: Paste. Ctrl + Z: Undo. Shift + Delete: Permanently delete the selected item without sending it to the Recycle Bin. Ctrl + Drag: Copy the selected item while dragging. Ctrl + Shift + Drag: Create a shortcut to the selected item while dragging. F2: Rename the selected item. Ctrl + Right Arrow: Move the cursor to the beginning of the next word. Ctrl + Left Arrow: Move the cursor to the beginning of the previous word. Ctrl + Down Arrow: Move the cursor to the beginning of the next paragraph. Ctrl + Up Arrow: Move the cursor to the beginning of the previous paragraph. Ctrl + Shift + Arrow Key: Highlight text or select multiple items. Ctrl + A: Select all. F3: Search for a file or folder. Alt + Enter: View the properties of the selected item. Alt + F4: Close the active window or program. Alt + Enter: Display the properties of the selected object Alt + Spacebar: Open the shortcut menu for the active window. Ctrl + F4: Close the active document. Alt + Tab: Switch between open applications. Alt + Esc: Cycle through open items in the order they were opened. F6: Cycle through screen elements in a window or on the desktop. Shift + F10: Display the shortcut menu for the selected item. Dialog Box Keyboard Shortcuts Ctrl + Tab: Move forward through the tabs. Ctrl + Shift + Tab: Move backward through the tabs. Tab: Move forward through the options. Shift + Tab: Move backward through the options. Alt + Underlined Letter: Select the corresponding option or command. Enter: Perform the command for the active option or button. Spacebar: Select or clear a check box or select a button. Arrow Keys: Move between options or items. F1: Display Help. Backspace: Open the folder one level up in Save As or Open dialog boxes. Microsoft Natural Keyboard Shortcuts Win: Open or close the Start menu. Win + Break: Open System Properties. Win + D: Show or hide the desktop. Win + M: Minimize all windows. Win + Shift + M: Restore minimized windows. Win + E: Open File Explorer. Win + F: Search for a file or folder. Ctrl + Win + F: Search for computers. Win + F1: Open Windows Help. Win + L: Lock the computer. Win + R: Open the Run dialog box. Win + U: Open Utility Manager. Microsoft Management Console (MMC) Main Window Shortcuts Ctrl + O: Open a console. Ctrl + M: Add or remove a snap-in. Ctrl + N: Open a new console. Ctrl + W: Close the console window. F5 key: Update the content of all console windows. Alt + Spacebar: Display the window menu. Alt + F4: Close the console. Alt + A: Open the Action menu. Alt + V: Open the View menu. Alt + F: Open the File menu. Alt + O: Open the Favorites menu. Internet Explorer Navigation Shortcuts Ctrl + B: Open the Organize Favorites dialog box. Ctrl + F: Open the Find utility. Ctrl + H: Open the History bar. Ctrl + I: Open the Favorites bar. Ctrl + L: Open the Open dialog box. Ctrl + N: Open a new browser window with the same webpage. Ctrl + O: Open the Open dialog box. Ctrl + P: Open the Print dialog box. Ctrl + R: Refresh the current webpage. Ctrl + W: Close the current window.