ops102_1_1.pdf

Introduction OPS102 Week 1 Class 1 Tiayyba Riaz/Chris Tyler May 5, 2024 Seneca Polytechnic Outline Introduction and How This Course Works What is an Operating System? Components of an Operating System User Interfaces A Bit of History OPS102 W1C1 - Introduction...

Introduction OPS102 Week 1 Class 1 Tiayyba Riaz/Chris Tyler May 5, 2024 Seneca Polytechnic Outline Introduction and How This Course Works What is an Operating System? Components of an Operating System User Interfaces A Bit of History OPS102 W1C1 - Introduction 1/27 Introduction and How This Course Works Welcome to OPS102 OPS102 – Operating Systems for Programmers An introduction to Linux and Windows For software developers First offered Fall 2023, replacing ULI101 for SDDS students See the official OPS102 course outline OPS102 W1C1 - Introduction 2/27 Course and Mark Breakdown Labs – 20% 10 labs throughout the term Quizzes – 25% 7 quizzes throughout the term, top 5 results are used Mid-Term Test – 25% Week 7, just before the study break Final Test – 30% Final week of the term OPS102 W1C1 - Introduction 3/27 Swapping Weeks 1 and 2 For OPS102 sections ZBB and NCC In calendar week one, I’ll present course week two material In calendar week two, I’ll present course week one material Why? Because I think the week two topics will help you in your other courses (e.g. IPC C Programming) OPS102 W1C1 - Introduction 4/27 What is an Operating System? What is an Operating System? Software that does “what it says on the tin”: it operates the computer system. Simple computers don’t need much of an operating system, if any: Early computers that ran only one program at a time Embedded systems, such as the computer (microcontroller) in a basic microwave oven, because it also runs only one simple program, doesn’t manage any sensitive information, and has no communication capability But for most contemporary computer systems, the operating system is a crucial component. OPS102 W1C1 - Introduction 5/27 What Does an OS Do? Four key things that an OS does: 1. Resource Management and Separation 2. Security Enforcement 3. Hardware Abstraction 4. Maintaining the Programming Model OPS102 W1C1 - Introduction 6/27 1. Resource Management A computer has finite resources – a certain amount of CPU capability, memory, storage, network bandwidth, and peripheral devices. The operating system is responsible for allocating these resources in a standardized manner to prevent conflicts. Examples: Ensuring that each program has its own unique area of memory so they don’t crash each other Preventing multiple programs from simultaneously sending output to the same peripheral, such as a printer, garbling the output OPS102 W1C1 - Introduction 7/27 2. Security Enforcement Information must be kept private in some contexts, but shared in others. The OS is responsible for enforcing security rules for both privacy and sharing. Examples: A social media app should not be able to access data from your banking app! One customer of a cloud server shouldn’t be able to access another customer’s data However, multiple smartphone apps might be permitted to access a single photo album OPS102 W1C1 - Introduction 8/27 3. Hardware Abstraction There are many hardware details that vary from system to system, such as the brand of GPU, size of the screen, and whether the keyboard is connected via USB or Bluetooth connection. The OS hides the details of the hardware so that application software can deal with the hardware in a consistent manner. Examples: A program can request input from the keyboard without knowing how the keyboard is connected An application can send data to the network in the same way regardless of whether the connection uses wired ethernet, WiFi, or 5G. OPS102 W1C1 - Introduction 9/27 4. Maintaining the Programming Model Programmers (Software Developers) need a single conceptual framework when creating software. The OS controls the hardware (and works with tools such as the compiler) to consistently maintain the illusion of the programmer’s model. Example: Multiple programs may be written to work in the same region of memory. The operating system will use the hardware virtual memory system to load those programs into different regions of physical memory but create the illusion that each one is in the same portion of memory, so that they can operate simultaneously without conflict. OPS102 W1C1 - Introduction 10/27 Components of an Operating System Components of an Operating System The four key components of an operating system are: 1. The Kernel 2. System Libraries 3. Services 4. User Interface(s) 5. Utilities and Applications OPS102 W1C1 - Introduction 11/27 1. The Kernel This is the heart of the Operating System – the main program Operates in a special Privileged Mode, which enables it to manage resources and security settings for all other software Loaded by the computer’s firmware (built-in software) Starts by setting up (initializing) the computer’s hardware and resources before starting the services and user interface(s) in non- privileged mode, programming the hardware to enforce the privilege level OPS102 W1C1 - Introduction 12/27 2. System Libraries Many programs perform the same operations: drawing on the screen, accessing the network, playing sound Libraries provide a common set of software routines (aka methods, procedures, subroutines, or functions) which programs access to perform these common operations This eliminates the need for each program to contain duplicate code for these common operations Although other libraries may be installed on the computer, the system libraries provided as part of the OS provide the most broadly-used routines, required by nearly every program OPS102 W1C1 - Introduction 13/27 3. Services These are programs that run continuously in the background, providing services such as WiFi authentication, print management, and file sharing. Unlike the kernel, these programs do not operate with full system privilege, and are subject to the same types of resource and security management as regular programs. They also use the system libraries. OPS102 W1C1 - Introduction 14/27 4. The User Interface(s) The user interface is the software enables the user to interact with the system. Most operating systems provide at least two types of user interfaces: A text-based user interface that enables the user to enter commands, view the output from those commands, and interact with full-screen text interfaces such as file editors and file managers. These may be referred to as text user interfaces (TUI) or command-line interfaces (CLI). A graphical user interface (GUI) that typically enables the user to interact with multiple application windows, typically using a keyboard and a pointing device such as a mouse/trackpad/touchscreen OPS102 W1C1 - Introduction 15/27 5. Utilities and Applications Most operating systems provide a set of tools to enable users to perform setup, configuration, and maintenance tasks. Utilities may use the GUI or CLI. Most operating systems also provide a set of basic starter applications, such as a text editor, clock, a few games, and sometimes a web browser. OPS102 W1C1 - Introduction 16/27 User Interfaces Command Line Interfaces: Windows, Linux OPS102 W1C1 - Introduction 17/27 Command Line Interfaces: Android OPS102 W1C1 - Introduction 18/27 Graphical User Interfaces: Windows OPS102 W1C1 - Introduction 19/27 Graphical User Interfaces: Linux OPS102 W1C1 - Introduction 20/27 GUI vs CLI: Strength and Weaknesses GUIs are well-suited to graphical tasks, such as editing images and documents. However, they may require excessive repetitive actions in some situations. CLIs are well-suited to automation, such as mass-conversion of thousands of images. However, they’re not well suited to occassional tasks. GUIs require far more data than CLIs. A typical CLI display contains about 2 kilobytes of data; a typical HD GUI display contains about 6 megabytes (6000 kilobytes) of data. Therefore, CLIs are often used over remote connections. OPS102 W1C1 - Introduction 21/27 Text User Interfaces A text user interface employs the same display technology as a CLI, but presents a full- screen interface rather than the scrolling command-and- response output used in a CLI. Before Microsoft Windows and the Apple Macintosh existed, this was the dominant form of interface on personal computers. Very common (still) in traditional business applications (e.g. your bank). OPS102 W1C1 - Introduction 22/27 Text User Interfaces OPS102 W1C1 - Introduction 23/27 A Bit of History A Bit of History In the very early days of computing, nothing was standardized – in fact, standardization was impossible, because many of the computers were one-of-a-kind! Many concepts in modern operating systems trace their roots to Multics, an OS developed at MIT starting around 1965. Bell Labs was involved with the Multics project, but withdrew early in its development. Two Bell employees who participated in Multics, Dennis Ritchie and Ken Thompson, went on to develop a smaller operating system using some of the same concepts, which they named Unix. OPS102 W1C1 - Introduction 24/27 Unix Unix was originally written for just one type of computer (as were most early operating systems) but was soon altered to be portable (useful on multiple, different types of computers) Unix was popular with the many different hardware vendors that existed at that time, because it eliminated the need for them to each develop their own operating system. Unix was also very popular in academia because the source code was widely available for study. Microsoft licensed the Unix operating system from Bell Labs and created a derivative called Xenix for small computer systems. OPS102 W1C1 - Introduction 25/27 CP/M and PC-DOS / MS-DOS Another popular operating system was CP/M (originally the Control Program/Monitor, later Control Program for Microcomputers) When IBM entered the microcomputer market in 1981, it contracted Microsoft to provide an operating system. Microsoft in turn licensed and later purchased 86-DOS from another company, renaming it PC-DOS (the IBM version) and MS-DOS (the version directly available from Microsoft). The design and internal structure of these operating systems was largely based on CP/M. Unlike Unix, DOS was a single-tasking system and did not have a heirarchical filesystem (nested folders or directories to organize large numbers of files). OPS102 W1C1 - Introduction 26/27 MS-DOS takes on Xenix Features As the IBM PC models – and compatible systems from other manufacturers – grew in their capabilities, it became necessary to extend DOS to take advantage of these mew features. Microsoft introduced features from Xenix (their version of Unix) into DOS starting with version 2.0 in 1983. Thus, DOS had a unique combination of Unix-like features, with some differences originating from its original CP/M-like heritage. For example, DOS couldn’t use the forward-slash in filenames, because that character was already being used for another purpose, so DOS pathnames used the backward-slash character (which was basically unknown before that time!). OPS102 W1C1 - Introduction 27/27 End of Class One! Lots of new ideas and concepts to digest Lots more to come! OPS102 W1C1 - Introduction 28/27