JB

User Interfaces for Operating Systems

User Interfaces for Operating Systems

Objectives

  • Explore different kinds of user interfaces for operating systems.
  • Focus on command line interface (CLI) and graphical desktop environments (GUI).
  • Emphasize the importance of the command line interface for automation.

User Interfaces to Operating Systems

  • Users cannot directly interact with the kernel; all interactions create new processes.
  • Types of user interfaces:
    • Command Line Interface (CLI)
    • Batch system
    • Graphical User Interfaces (GUI)
    • Text-Based User Interface (TUI): similar to CLI, uses keystrokes for actions

Dominance of User Interfaces

  • Traditional OS (Windows, macOS, Android, Chrome OS, iOS): GUI is dominant.
  • Linux: Choice between CLI and GUI (desktop environments).
  • Servers: CLI is often the default due to resource efficiency.

CLI vs. GUI

  • CLI can appear scary but becomes easy with practice.
  • Advantages and disadvantages exist for both, choice depends on the task.

CLI

  • Powerful for automation.
  • Requires memorization of commands (hundreds or thousands, but only about 20 are used daily)
  • More precise (e.g., typing a number is more exact than using a slider).
  • Less forgiving (syntax errors cause errors).

GUI

  • More user-friendly and easy to learn.
  • More forgiving (lenient with mouse clicks, etc.).
  • Can represent more than just text (images, videos, sounds).
  • Designers try to cater to all possible uses, but inherently less power than CLI

Efficiency and Resources

  • Experienced CLI users are faster than GUI users.
  • GUI offers a richer experience in terms of communication.
  • GUI requires more resources, making CLI preferable for servers.

Shell and Terminal

  • CLI involves running a program (shell) that communicates with the kernel.
  • Shell: Application that takes typed commands and executes them via system calls.
  • Shells are appearing in GUI-oriented OS like Windows.

POSIX Systems Shells

  • Born shell
  • C shell
  • Born Again Shell (Bash): most common, to be used in the course
  • K Shell
  • Z Shell: Default on macOS, can switch to other POSIX shells

Microsoft Windows Shells

  • PowerShell: Similar to bash, different syntax, used for Windows system administration

Shell Functionality

  • Shell interprets commands, defines environment with variables.
  • Enables shell scripts for automation (repetitive tasks, system checks, combining commands).

Demo of Shell

  • Windows Terminal (PowerShell):

    • ls: Lists files in the current directory.
    • pwd: Shows the current directory.
    • whoami: Shows the current user.

  • Secure Shell (SSH) to remote Linux machine (Bash shell):

    • Uses password for secure connection.
    • NeoFetch tool to show Linux distribution info.

Common Commands

  • man: Manual pages for command documentation.
  • ls: List directory contents.
  • cd: Change directories.
  • rm: Remove files.
  • cp: Copy files.
  • mv: Move files.
  • pwd: Present working directory.
  • Commands to show the contents of a text file.

Batch Interface

  • Used in high-performance computing for automating long-running applications.
  • Batch scheduler manages jobs based on resource availability.

Graphical User Interface (GUI)

  • Familiar to most users (Windows, macOS).
  • Uses a desktop metaphor with icons.
  • Mouse, keyboard, and touchscreen control actions.

GUI Processes

  • Background desktop and icons are managed separately.
  • Panels (start menu, taskbar) are separate processes.
  • Window manager: Manages resizing, moving, and hiding windows.
  • Applications control what is displayed inside their windows.

POSIX GUI System - X Window Environment (X)

  • XServer: Controls graphics cards, keyboard, and mouse input.
  • XClients: Applications (word processor, etc.) making draw requests to the XServer.
  • Window manager: Special XClient that manages windows.

Window Managers

  • Choice of window manager in Linux affects window operations and animations.
  • Customizable buttons (close, maximize, minimize).
  • Tiling support: Some window managers offer tiling for efficient window arrangement.

Tiling Window Manager Example

  • Linux virtual machine (PopOS) with tiling window manager.
  • Applications automatically take up available screen space.
  • Efficient for workflows like programming, especially with keyboard shortcuts.
  • Workspaces: Ability to have multiple activities on different workspaces.

Desktop Environments

  • Suite of XClients and a window manager providing an integrated desktop experience.
  • Examples: GNOME, KDE, Mate.
  • Can install multiple desktop environments and choose which to use.

Desktop Environment Considerations

  • Resource usage: KDE and GNOME require more resources.
  • Special effects: Some offer more visual effects.
  • Window management: Tiling vs. traditional.

Key Takeaways

  • Familiarity with terminal applications and shells (PowerShell, BashShell, Z Shell) is crucial.
  • Understanding different desktop environments allows for customization based on needs and resources.