Module 5: Operating Systems

Computers run two general types of software (SW):

• systems SW

• application SW.

Systems SW

•  consists of the programs (operating system and utility tools) that allow you to manage, control and operate your computer--and allow it to run application SW. 

  • Most system SW programs are preinstalled on your computer when you purchase it.

Application SW

• normally must be purchased, allows users to perform specific hobby or business-related tasks–

  • such as writing a letter, playing a game or printing payroll checks.

System SW

• usually divided into two categories: the operating system (OS) and utility tools (programs).

An OS is the main collection of programs that manages a computer’s activities. 

• The primary tasks: management and control. 

• It manages application SW instructions and acts as a middle-man between the user and the computer and between application programs and the computer hardware.

  • Without an OS, a computer cannot run.

The primary functions of an OS are:

• Booting up the computer and starting programs

• Interfacing with users

•  Managing programs

• Managing memory

• Coordinating tasks

• Configuring devices and loading device drivers

•  Monitoring performance

• Establishing an Internet connection

• Updating OS software

• Controlling a network

• Administering Security

Booting up the computer and starting programs

• loading parts of the OS (called the kernel) and loading startup programs (such as an antivirus) into RAM.

• Manual (power button) or automatic shutdown of the computer

Interfacing with users

• translating user instructions into a form the computer understands and vice versa. 

  • Most computers use a graphical user interface (GUI) that enables the user to give commands to the computer by clicking on icons with a mouse or using a touch screen monitor to press on icons with a finger. Some Linux and Unix operating systems (and the PC command prompt window) use a command-line interface that requires the user to enter specific commands to perform functions.

 Managing programs

• more than one program is simultaneously open the OS manages what program is in the foreground (visible on the monitor) and which are running in the background. The OS also enables users to install and uninstall programs.

Managing memory

• The OS keeps track of how much RAM has been used and how much RAM space is available.

• If RAM gets full the OS automatically allocates part of the hard drive to function as "virtual memory".

• The OS then swaps "pages" (chunks of data or programs) back and forth between RAM and virtual memory until virtual memory is no longer needed.

• Data retrieved from virtual memory takes longer to process than data retrieved from RAM.

Coordinating tasks

• The OS determines the order in which tasks are processed.

  • Tasks such as receiving data from an input device, processing instructions, sending information to an output device and transferring data from storage to memory and from memory to storage.

    • also manages print jobs sent to the printer.

Configuring devices and loading device drivers

• that enable the OS to communicate with attached hardware devices. 

  • When a new hardware device is connected to the computer, the OS automatically locates the device driver for that device and sends it to RAM.

  • This process is often referred to as "Plug and Play"

Monitoring performance

• Most OS's include a performance monitor program that assesses and reports information about various computer resources and devices (CPU, hard drives, memory, network).

• The information in performance reports helps identify a problem with system resources.

Establishing an Internet connection

• OS's typically provide ways to connect to the Internet using both wired (cable, DSL) and wireless (WIFI) technologies

Updating OS software

• Most OS's have an automatic update feature that regularly provides new features or corrections to the OS and provides security updates

Controlling a network

• Network operating systems (NOS's) installed on server computers enable the server to share network resources (Internet, programs, files, storage, RAM, CPU) with multiple users.

Administering Security

• The OS keeps track of usernames, passwords and biometric characteristics to restrict who has access to the computer and its resources. 

  • include built-in firewalls and/or antivirus programs to protect against hacker attacks.

Know the functions of the utility tools

• Multitasking

• Multithreading

• Multiprocessing

Multitasking

• provides process and memory management services that allow two or more tasks, jobs, or programs to run simultaneously.

Multithreading

• Within a single program, it allows multiple commands, or threads, to run simultaneously.

• For example, one thread for a spreadsheet program might be waiting for input from the user while other threads perform a long calculation in the background.

  • can speed up performance on single- or multiple-processor devices.

Multiprocessing

• Many digital devices include multi-core processors or multiple processors.

• An operating system's multiprocessing capability supports a division of labor among all the processing units.

The OS works closely with the CPU to perform four different processing techniques. Not every OS is capable of all four.

• Multitasking

• Multithreading

• Multiprocessing

• Parallel processing

Multitasking

• the ability of an OS to have more than one program open at a time.

• Without multitasking ability, an OS would require the user to close one program or document before opening another.

• Computers multitask by using a time-sharing technique in which the CPU spends a fixed amount of time on each program.

Multithreading

• A thread is a sequence of instructions within a program that is separate from other threads.

• An OS that supports multithreading has the ability to rotate time between multiple threads which optimizes program performance

Multiprocessing

• is using multiple CPUs (or two or more cores on a single CPU) to perform work on different jobs at the same time.

• Server computers often perform multiprocessing when handling simultaneous requests for multiple resources (such as printing, email retrieval, and programs)

Parallel processing

• is using two or more CPUs located on one computer to work on a single program at the same time in order to complete the program quicker. Parallel processing is used most often with supercomputers

• Types of operating systems:

•  Command line interface OS

• Graphical user interface (GUI) OS

•  A desktop OS

• A network OS (NOS)

 Command line interface OS

• require the user to type commands using the keyboard in order to give instructions to the computer (some versions of UNIX and Linux)

Graphical user interface (GUI) OS

•  allows the user to issue commands by selecting icons, buttons, and other graphical objects with a mouse, finger, or stylus pen.

 A desktop OS

• is designed to be used by one person on a single computer. 

  • Computers with a desktop OS are sometimes called client computers.

A network OS (NOS)

• is installed on a server computer. The NOS provides client computers access to network resources (programs, files, storage, printers, etc.) located on (or connected to) the server computer.

Common desktop operating systems are:

• Microsoft Windows

• Apple macOS is the proprietary OS for computers

•  Linux is similar to UNIX

• Google Chrome OS is a Linux-based OS

Microsoft Windows

• Windows is the most common desktop OS.

• Many computer vendors (Hewlett Packard, Dell, Acer, etc.) use Windows as their default OS. Computers with a Windows OS are often called personal computers (PCs).

• PCs have Edge as the default browser and use OneDrive as its cloud server. Windows 11 is the most recent version of Windows.

Apple macOS is the proprietary OS for computers

• made by Apple Corporation. It enables a Mac computer to communicate with other Apple devices such as phones and watches.

• Mac computers use Safari as the default browser and iCloud as its cloud server. Monterey (also known as Mac OS 12) is the most recent version of macOS.

 Linux is similar to UNIX

• However, unlike other desktop OS's, it is an open source OS, which means no company owns the rights to the operating system code.

• Thus, there are many different versions of Linux (Ubuntu, Mint, Fedora, Debian, Kali, etc.).

• Many versions of Linux can be downloaded and installed for free.

• While some versions of Linux use a command-line interface, most have a GUI.

Google Chrome OS is a Linux-based OS

• that runs on the Google Chromebook laptop. Chrome OS was created to work mostly with web apps that are available through the Chrome Web Store.

• Chrome OS uses Chrome as its default browser and Google Drive as its cloud server.

Users who want to have multiple OS's on the same computer can do so by

• by partitioning the hard drive or by using a Virtualization program to create multiple virtual machines.

• Each virtual machine can have a different OS.

• A virtual machine is a file that, when opened, acts like a physical computer.

• Because it is a file, a computer can have many different virtual machines. 

virtual machine (VM)

• allows one computer to simulate the hardware and software of another.

• Each virtual machine has its own simulated processor, RAM, video card, input and output ports, and operating system.

• Each machine can run most software that's compatible with the virtual OS platform.

Popular virtual machine software such as VMware Workstation and Parallels Desktop

• can run on most computers with Intel microprocessors, including Intel Macs. PCs, and generic Linux computers.

• The computer boots into its native OS, such as macOS, but users can then launch a virtual machine running guest operating systems, such as Windows.

• The virtual machine's desktop appears in a window on the host desktop

Common network OS's (also called server OS's) are:

• Microsoft Windows Server

• Oracle UNIX

• Linux is an open-source NOS

Microsoft Windows Server

• Is the most widely used NOS. It has a similar GUI and is highly compatible with Windows desktop operating systems.

• The current version is Windows Server 2022.

Oracle UNIX

•  is not as popular as the Windows and Linux NOSs. 

  • It is mostly used to run web servers.

Linux is an open-source NOS

• that is similar to Unix. Linux’s free, stable, secure, open-source SW has made it a popular alternative to Windows and UNIX as an NOS. 

  • Linux is often used by web servers and supercomputers.

Mobile devices require their own specialized operating systems.

• The three most common mobile OS’s are listed below.

• Android is a Linux-based OS

• iOS is the Apple OS

• Windows (Mobile Edition)

 Android is a Linux-based OS

• designed by Google and used by many mobile phone manufacturers

iOS is the Apple OS

• designed for Apple iPhones and iPads

Windows (Mobile Edition)

• is Microsoft’s OS for smartphones. It is not near as popular as Android and iO