Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Overview of the Linux & UNIX Operating Systems Instructor: Joseph DiVerdi, Ph.D., MBA

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Computer Usage Computer is a Tool for Solving Problems –For Most of Us When Running a Word Processor –A Tool for Arranging Words & Ideas When Running a Spreadsheet –A Financial Planning Tool When Connected to an Electronic Network –Tool in a Powerful Communications System Computers Are Very Different Than Other Tools...

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Need for Software What's the Difference Between –A Gas-Powered Weed Whacker & –A Desktop Computer Or Perhaps –A Gas-Powered Weed Whacker & –A Computer-Controlled Gas-Powered Weed Whacker In Both Cases One Is Useless Without Software –Perhaps Useless With Software

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Need for Software Non-computer-controlled Devices –Have Their Total Functionality Established at Birth –Require No Additional Information to Accomplish Their Missions Maybe Not So for Their Users Computer-controlled Devices –Have Their Basic Functionality Established at Birth –Require Additional Information to Accomplish Their Missions Programming Instructions –Software

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Need for Software Consider the Utility a Desktop Computer –Without Any BIOS Boot ROM, Etc. –With an Absolutely Empty Disk Useful As an Anchor or Room Heater

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Need for Software Software Provides Functionality to Computers –And All Computer-controlled Devices That's Nice... –Functionality Is Not Fixed at Birth It Can Be Increased at Later Times That's Bad... –Expectations Cause Humans to Create Software With Problems Bugs (or Features)

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Kinds of Software Software Can Be Broken Up Into Bits –Operating System –Applications All Can Be Called Programs

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Operating System At the Heart of Every Computer –A Master Set of Programs Called Operating System –Controls Input/Output Systems Keyboard, Disk, Network Interface –Defines Set of Mechanisms & Policies Control Sharing of System Resources –Provides Tools for Common Operations File Access

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Operating System Parts Kernel –Services Which Interact Directly With Hardware File System –Logical Method for Organizing & Accessing Info Shell –Prime User Interface Utilities –Extensible Tool Set for Common Operations Applications –Extensible Tool Set for Performing Work

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC OS - Kernel Large Program Loaded Into Memory When Turned On –Booting Interacts Directly With Hardware –So Others Don't Have To Creating Hardware Interface Software Is –Difficult –Situation-specific –A Real Pain –Others Benefit From Hardware-independent Access Same Program Works on Different Hardware

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC OS - Kernel Major Functions –Manage Computer Memory –Control Computer Access –Maintain File System –Handle Events Through Interrupt System –Handle Errors –Perform Input/output –Allocate System Resources Among Processes Memory, CPU Time

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC OS - File System Logical Method for Organizing, Storing, Retrieving, Manipulating, & Managing Info Basic Unit of Information Is File Files Are Organized Into –Hierarchical File System –Files Grouped Together Into Directories Also Physical Devices Are Treated As Files –Important Simplifying Feature –Same Commands Work for Files & Devices

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC OS - Shell Reads User Commands –Interprets Each As Request to Execute a Program –Called Command Interpreter –Also Called Command Line Interpreter (CLI) Acts As Programming Language –Permits Commands to Be Connected Together Very Different From – Graphical User Interface (GUI) –Used in Desktop Oss Windows, Macos, Etc.

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC OS - Utilities Several Hundred Programs –Generally Small Programs Carry Out a Single Function –Some Are Quite Large Carry Out Several Functions –Also Known As Tools –Can Be Used Separately –Can Be Put Together To Carry Out Useful Tasks –Integral Part of UNIX Philosophy

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC OS - Applications User Interacting Programs –Utilize Underlying Utilities & Tools –Some Are Part of OS Supplied With Installation Software –Some Are Third-party Added Functionality After-the-fact

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC UNIX Philosophy A Powerful & Complex Computer System –Should Still Be Simple, General, & Extensible Provides Benefits for Both Users & Developers Learn It Once - Use It Everywhere Small Is Beautiful Single File System Model –Directories, Ordinary Files, Devices Are Viewed The Same Way Printer, Disk, Keyboard, Terminal Screen, Network –Underlying Hardware Details Are Hidden Get Information From Anywhere The Same Way

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC UNIX Philosophy Large Collection of Utility Programs –Each Designed to Perform a Specific Function All Designed to Work Together Instead of a Few Large Programs –Each Trying to Accomplish Many Functions Which Don't Interact Effectively –Thought of As Set of Modular Tools

Linux & UNIX OS Overview Fort Collins, CO Copyright © XTR Systems, LLC Operating System Parts Kernel –Services Which Interact Directly With Hardware File System –Logical Method for Organizing & Accessing Info Shell –Prime User Interface Utilities –Extensible Tool Set for Common Operations Applications –Extensible Tool Set for Performing Work