Operating System — Install & Optimise

What is an operating system?

• An operating system (OS) is system software that manages computer hardware, manages software resources, and provides common services for computer programs.
• It is the most important software on a computer. Without an OS, a computer is useless.
• The OS is initially loaded into the processor by a boot program. It then manages all other programs, which are called applications or tasks.
• The OS acts as an intermediary between programs and hardware for functions such as input/output and memory allocation. Application code is usually executed directly by hardware, but it frequently makes system calls to an OS function or is interrupted by it.
• OS is found on many devices: cellular phones, video game consoles, web servers, supercomputers.

Figure 1.1 — Functionality

The diagram shows four layers, with arrows going both up and down:

• User (top)
• Application
• Operating System
• Hardware (bottom)

The OS sits between applications and hardware and manages communication both ways. It receives requests from applications and controls hardware, then provides services back to applications.

Purpose of an OS

• Manage computer memory.
• Manage processes.
• Manage the operation of all hardware and software.
• Enable computer hardware to communicate effectively with all other computer software.

Functions of an OS (pages 8–10)

1. Program execution — executes all types of programs, whether user programs or system programs.
2. Handling input/output operations — handles all inputs from keyboard, mouse, desktop, etc., and all interfacing for inputs and outputs.
3. Manipulation of file system — decides how data/files are stored and manipulated on floppy disk, hard disk, pen drive, etc.
4. Error detection and handling — detects errors or bugs during tasks; a well-secured OS also acts as a countermeasure against breaches from external sources.
5. Resource allocation — decides which resource is used, by whom, and for how much time.
6. Accounting — tracks an account of all functionalities taking place at a time; records details such as types of errors.
7. Information and resource protection — uses all information and resources in the most protected way; prevents external resources from damaging data.
8. Security — uses password protection to protect user data; prevents unauthorized access to programs and user data.
9. Control over system performance — monitors overall system health; records response time between service requests and system response to troubleshoot problems.
10. Job accounting — keeps track of time and resources used by various tasks and users.
11. Error detecting aids — constantly monitors the system to detect errors and avoid malfunctioning.
12. Coordination between other software and users — coordinates and assigns interpreters, compilers, assemblers, and other software to users.
13. Memory management — manages primary/main memory: tracks used/free memory, allocates memory when requested, deallocates when a process ends or does I/O, and decides access order in multiprogramming.
14. Processor management — decides order of process access to the processor and how much processing time each gets (called process scheduling). The program that keeps track of process status is called a traffic controller. Allocates and deallocates the CPU.
15. Device management — manages device communication via their respective drivers. The program responsible for every device is the Input/output controller. Decides which process gets access to a device and for how long; allocates and reallocates devices.
16. File management — a file system is organized into directories for efficient navigation. The OS keeps track of where information is stored, user access settings, and status of every file. These facilities are collectively known as the file system.

Batch operating system (page 11)

• Users do not interact directly with the computer.
• Each user prepares a job on an off-line device like punch cards and submits it to the computer operator.
• Jobs with similar needs are batched together and run as a group.
• The operator sorts programs with similar requirements into batches.

Problems with batch systems:

• Lack of interaction between the user and the job.
• CPU is often idle because mechanical I/O devices are slower than the CPU.
• Difficult to provide the desired priority.

Real-time operating system (page 11)

• A real-time system is a data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment.
• The time taken to respond to input and display updated information is called response time. In real-time systems, response time is very small compared to online processing.
• Used when there are rigid time requirements on processor operation or data flow; can be a control device in a dedicated application.
• A real-time OS must have well-defined, fixed time constraints; otherwise the system will fail.
• Examples: scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, air traffic control systems.

Hard real-time systems:

• Guarantee critical tasks complete on time.
• Secondary storage is limited or missing; data is stored in ROM.
• Virtual memory is almost never found.

Soft real-time systems:

• Less restrictive.
• A critical real-time task gets priority over other tasks and retains priority until it completes.
• Limited utility compared with hard real-time.
• Examples: multimedia, virtual reality, advanced scientific projects like undersea exploration and planetary rovers.

Multi-tasking operating system (page 12)

• Means the need to time-share the CPU so things happen in time.
• Fractional slices of a second are allotted to many demands lined up for the CPU.
• In multi-tasking, it is no longer the program sequence that determines what happens next; the operating system controls it.
• Key concepts: tasks, deadlines, priorities.
• A system operating in real time is one that can meet its deadlines. Sophisticated multi-tasking real-time systems require a real-time operating system (RTOS).

Comparison table: batch vs real-time vs multi-tasking

Feature	Batch OS	Real-Time OS	Multi-Tasking OS
User interaction	None / not direct	Usually dedicated; limited direct interaction	Interactive; many tasks compete
Response time	Slow; jobs run in batches	Very small / fixed	Time-sliced; depends on scheduling
Main idea	Group similar jobs	Meet rigid time constraints	Time-share CPU among tasks
CPU use	Often idle due slow I/O	Must meet deadlines	OS switches between tasks
Priority	Difficult	Critical tasks prioritized; hard/soft types	Priorities and deadlines important
Examples	Payroll batch, punch-card jobs	Air traffic control, robots, medical imaging	Modern PCs, embedded systems

Microsoft Windows (pages 13–14)

• Created by Microsoft in the mid-1980s. Versions: Windows 10 (2015), Windows 8 (2012), Windows 7 (2009), Windows Vista (2007).
• Comes pre-loaded on most new PCs, making it the most popular OS in the world (more than 80% market share).
• Operability: compared to Linux and macOS, Windows operability is poor, yet it is the most popular OS. Poor features: frequent crashes, slowing down over time, virus, error codes, memory leak, blue screen of death, black screen, WiFi issues, battery problems, apps suddenly stopping.
• Features: shows available physical memory, cached OS code, allocated pool-paged-resident and pool-nonpaged memory, CPU time on user/system processes; Start menu, tablet mode in Windows 10, game center connected with XBOX, multiple desktops and task views, Cortana assistant manager, unified settings and action center.
• Strength: good GUI, easy to learn, lots of productivity apps, good gaming functionality and support, app store, decent diagnostic and administrative tools, easier setup than Linux, large support base.
• Weakness: costly; some services require paid subscriptions; less secure than Linux and macOS; can slow over time; requires frequent updates which sometimes fail.
• Competitive edge: based on Office and cloud products, Morningstar gives Microsoft a significant economic moat. Three divisions: more personal computing, intelligent clouds, productivity and business processes.

macOS (pages 15–16)

• Previously called OS X; created by Apple; preloaded on all Macintosh computers/Macs.
• Versions: Mojave (2018), High Sierra (2017), Sierra (2016).
• Market share: less than 10% of global OS. One reason: Apple computers tend to be more expensive.
• Operability: more operable than Windows because it is proprietary. Apple develops both hardware and OS, so fewer issues. Consistent performance, security and support. Quality user experience is a top priority.
• Features: proprietary hardware; completely integrated system where hardware and software interact flawlessly; iCloud lets Mac apps communicate with iOS devices.
• Strength: fewer virus attacks than Windows, good customer support, consistent GUI for all products, great speed and availability, superior hardware provides long life, supports Windows file system and can run Windows.
• Weakness: most expensive, less software than Windows, poor support for gaming, no hardware customization, no cloud or server services like Windows and Linux.
• Competitive edge: security, ease of use, hardware-software harmony, superior hardware quality. “With Apple, you are in control.”

Linux (pages 16–18)

• A family of open-source operating systems. Open source means they can be modified and distributed by anyone around the world.
• Advantages: free; many distributions/versions.
• Market share: less than 2% of global OS. However, most servers run Linux because it is relatively easy to customize.
• Operability: easily defeats Windows in speed; reduces “bogging” with many processes; Ext4 file system maintains device efficiency; no longer supports defragmentation; benefits from privacy; built-in cutting-edge encryption; safer than Windows; open-source technology lets anyone review vulnerabilities. Emphasizes uptime, process control and system security.
• Components: boot loader, kernel, init system, daemons, graphical server, desktop environment, various applications.
• Features: shows total system memory used, cached, buffered, or free; CPU time on system/user duties; stealing jobs from virtual OS; waiting for I/O; processing nice tasks; amount of work like Windows/macOS; growth/reduction in disk space used; disk utilization, queuing, latency, throughput.
• Strength: less battle with viruses, malware, slowdowns, crashes, costly repairs, licensing fees; open source (flexible, easy changes, shared/updated); many versions for every user type; almost all distributions free to download, burn, install on as many machines as you like.
• Weakness: some device drivers unavailable; hardware manufacturers prefer Windows/Mac; beginners find Linux challenging; CLI requires learning; finding new software can be challenging; troubleshooting difficult; fewer experts; few software alternatives (Photoshop, Microsoft Office not on Linux; games typically for Windows).
• Competitive edge: appeals to customers who prioritize security, speed, cost and ease of maintenance; subscription-based pricing; no fees for version upgrades; compact footprint; cost reduction opportunities; IBM server benefits such as dynamic memory upgrade on mainframes and live partition mobility on Power Systems.

Virtual memory (page 19)

• Virtual memory is a technique that allows the execution of processes which are not completely available in memory.
• Main visible advantage: programs can be larger than physical memory.
• Virtual memory is the separation of user logical memory from physical memory. This separation allows an extremely large virtual memory to be provided for programmers when only a smaller physical memory is available.

Situations when the entire program is not required to be loaded fully in main memory:

1. User-written error handling routines are used only when an error occurs in data or computation.
2. Certain options and features of a program may be used rarely.
3. Many tables are assigned a fixed amount of address space even though only a small amount is actually used.
4. The ability to execute a program that is only partially in memory would counter many benefits.
5. Less I/O would be needed to load or swap each user program into memory.
6. A program would no longer be constrained by the amount of physical memory available.
7. Each user program could take less physical memory; more programs could run at the same time; CPU utilization and throughput increase.

Figure 1.5 — Virtual Memory: The diagram shows Virtual Memory (Page 0, Page 1, Page 2, … Page n) on the left, a Memory Map in the middle, Physical Memory (frames/slots), and Backing Store (disk storage) on the right. Arrows show pages being mapped from virtual memory to physical memory and backing store. Meaning: not all pages of a program need to be in physical RAM at once; some pages can be stored in backing store and loaded when needed.

Technical requirements (page 23)

• Technical requirements (also called technical specifications or specs) refer to the implemented solutions professionals use to resolve technical problems and issues involving software.
• They describe the technical aspects and issues you need to address for a project or software to work and execute successfully. They can refer to performance-related concerns, reliability of software, and accessibility.
• Technical requirements function as solutions to technical issues.
• Example: You create online word processing software that only works for a specific web browser because of an important integration system. In this scenario, “must use a specific browser” is the technical requirement.

Why technical requirements are important:

• They describe how software should function and what its behavior should be.
• They help developers and users understand the best way to use the software.
• A document of clearly defined specifications helps create a project/software with a proper process for implementation.
• Developers and technicians refer to this as technical requirement documentation.
• The universal goal is to ensure software owners and developers have an established understanding of future details and project estimations.
• Project estimations include cost estimates, resource allocating, and the duration of development. Knowing technical requirements helps determine these factors more precisely.

The 17 technical requirements (pages 24–26)

#	Technical requirement	Meaning / example
1	Accessibility	Makes service/software/technology accessible to all users. Example: closed captions for deaf/hard-of-hearing users.
2	Authentication and authorization	System must abide by authentication and authorization policies. Authentication assesses data as valid; authorization gives clearance for access.
3	Availability	Metric tracking time as a percentage; verifies how long software/resource is available for users.
4	Data quality	Data/information must be of a certain quality; ideally high-quality for operations and decision-making.
5	Human error	Software detects when people input inaccurate information, notifies user, advises fix.
6	Information security	Encryption and security of user credentials and personal private information in online storage or transit; includes encrypting highly classified information.
7	Internal controls	Only certain users can access decryption keys for encrypted user and highly classified data. These individuals are called data stewards; they can access data only when a higher official allows.
8	Interoperability	Software must offer comprehensive compatibility: work on all major OS, web browsers, technical devices. May depend on customer technology needs.
9	Maintainability	Software must maintain integrity; system needs to identify and resolve technical problems in a set timeframe. Most repairs need to resolve in only an hour.
10	Performance	Determines average wait times and how long software/page takes to load. Best practice: load times should not exceed two seconds.
11	Privacy	Protects customer’s sensitive data from internal data professionals and employees. Example: employees may not view a customer’s social security number.
12	Productivity	Processes that let users be more productive. Example: system auto-generates data so users skip inputting data multiple times.
13	Reliability	Average time a system/software operates between downtimes or failures; metric averaging time for critical applications/services.
14	Serviceability	Systems must not completely shut down when software upgrades or changes occur.
15	Standards	System/software must follow and comply with security and architectural requirements; design/structure for flexibility, reusability, feasibility.
16	System errors	When system has an error, an error code communicates the discrepancy with the user; documented in a help database; helps service the incident to a swift resolution.
17	Vendor lock-in	Textbook definition: software/system is open-sourced; not owned by a proprietary/private company; available to be manipulated with custom code by any user.

Boot methods (page 27)

• USB — use a USB drive as boot media when no CD/DVD. Must create a bootable USB using programs, then copy the OS to the USB flash drive. Advantage: can update information on the flash drive, useful when installing many computers.
• CD-ROM — Windows installation media is often stored on CD-ROM. The computer must have a built-in CD-ROM reader or an external reader.
• DVD — similar to CD-ROM. The computer must have a DVD-ROM reader. If the reader is absent, you cannot install an OS stored on that media.
• PXE (Preboot Execution Environment) — capability present in most computers that allows automatic installation of an OS whose files are on a network drive. Physical media is not required.

Mnemonic: U-C-D-P = USB, CD-ROM, DVD, PXE.

Types of installations (pages 27–28)

1. Creating image — installer creates a Windows OS that is a clone by taking an existing OS version and making sector copies of everything on the computer.
2. Unattended installation — common in large organizations. The IT expert/installer does not need to be present to respond to prompts. Create an unattend.xml file with all answers to questions and responses to prompts; customize the XML file in the Windows installation media; installation runs by itself.
3. Upgrade — in-place upgrade. Installation begins with the previous OS present. Once it identifies the existing OS, it automatically upgrades to the latest version without altering applications or files.
4. Clean install — different from in-place upgrade. Erases every file on the computer. Requires backup of important files (external hard disk or cloud). Erases all documents and configured personal settings. Move items to a separate drive before installation to avoid losing them.
5. Repair installation — used when OS files are corrupted/damaged due to bad hard drive section, virus, Trojan, etc. Windows installation shows repair options. Reinstalls OS files again without configuration changes or hard drive modifications. Simply repairs OS files on the Windows version.
6. Multi boot — also called dual boot. Install a new OS without removing the old OS. Two different OS on two distinct hard drive partitions. On start-up, a prompt asks which OS to run. Example: Windows 7 and Windows 8 on one computer. To switch, restart the computer.
7. Remote network installation — no physical media required. Put Windows installation files and configurations on a network drive. PXE lets the system run onto the network and access installation files. Need a single centralized server to undertake the installation.
8. Image deployment — cloning the OS image to another PC when the machine needs to be deployed. On start-up, Windows information is similar to the old system; no need to go through the installation program when bringing the computer onto the network.

Partitioning (page 28)

• Hard drive partitioning is a prompt during Windows installation, especially first-time installation.
• Master Boot Record (MBR) partition table — supports four partitions on one hard disk.
• Globally Unique Identifier (GUID) partition table — supports 128 partitions.

Dynamic disk partition: has the capability to deny addition of any new drive in addition to spanning data from the basic partition into the newly installed drive. Supported by several Windows operating systems.

Basic disk partition: an idea of Microsoft. It has a Disk Operating System or Windows installed on it. It can bear primary and logical partitions, with logical drives included.

Module basics

• Module code: EIS HNS2 M02 1221
• Nominal duration: 40 hours
• Prepared by: Ministry of Labour and Skill, August 2022, Addis Ababa
• Four units: Function of OS; Obtain OS; Install/configure/optimize OS; New software requirements
• Acronyms: OS = Operating System; FAT = File Allocation Table; NTFS = New Technology File System; CDFS = Compact Disk File System

OS definition and purpose

• OS: system software that manages hardware, manages software resources, provides common services for programs.
• OS loaded by: boot program.
• Other programs are called: applications or tasks.
• OS acts as: intermediary between programs and hardware for I/O and memory allocation.
• Without OS: computer is useless.
• Figure 1.1 layers (top to bottom): User → Application → Operating System → Hardware.
• Main purpose: manage memory, processes, operation of all hardware and software.

OS functions (know all 16)

1. Program execution — executes user and system programs
2. Handling input/output operations — keyboard, mouse, etc.
3. Manipulation of file system — decides how data/files stored
4. Error detection and handling — detects bugs; countermeasure against breaches
5. Resource allocation — which resource, by whom, for how long
6. Accounting — tracks all functionalities; records error types
7. Information and resource protection — protects data from external damage
8. Security — password protection; prevents unauthorized access
9. Control over system performance — monitors health; records response time
10. Job accounting — tracks time and resources used by tasks/users
11. Error detecting aids — constantly monitors for errors
12. Coordination between other software and users — assigns interpreters, compilers, assemblers
13. Memory management — manages primary/main memory; allocates/deallocates; tracks used/free
14. Processor management — process scheduling; traffic controller; allocates/deallocates CPU
15. Device management — via drivers; I/O controller; allocates/reallocates devices
16. File management — directories; tracks storage, access settings, file status; file system

• Traffic controller: program that keeps track of process status.
• I/O controller: program responsible for every device.
• Process scheduling: OS decides order of process access to processor and time each gets.

Batch OS

• Users: do not interact directly with computer.
• Jobs prepared on: punch cards (off-line device).
• Jobs with similar needs: batched together and run as group.
• Problems (3): lack of interaction; CPU often idle (slow mechanical I/O); difficult to provide desired priority.

Real-time OS

• Definition: data processing system where time interval to process/respond is so small it controls the environment.
• Response time: time to respond to input and display updated information.
• Must have: well-defined, fixed time constraints (otherwise system fails).
• Examples (6): scientific experiments; medical imaging; industrial control; weapon systems; robots; air traffic control.
• Hard real-time: guarantees critical tasks complete on time; secondary storage limited/missing; data stored in ROM; virtual memory almost never found.
• Soft real-time: less restrictive; critical task gets priority and retains it until completion; limited utility; examples: multimedia, virtual reality, undersea exploration, planetary rovers.

Multi-tasking OS

• Means: time-share the CPU so things happen in time.
• Fractional slices of a second allotted to many demands.
• OS controls what happens next (not program sequence).
• Key concepts (3): tasks, deadlines, priorities.
• Sophisticated multi-tasking real-time systems require: real-time operating system (RTOS).

Windows

• Created by Microsoft: mid-1980s.
• Versions: Windows 10 (2015), 8 (2012), 7 (2009), Vista (2007).
• Market share: more than 80% (most popular).
• Operability: poor compared to Linux/macOS (frequent crashes, slowing, virus, error codes, memory leak, blue screen, black screen, WiFi issues, battery problems, apps stopping).
• Features: Start menu; tablet mode in Win 10; game center with XBOX; multiple desktops/task views; Cortana; unified settings/action center.
• Strength: good GUI, easy to learn, lots of productivity apps, good gaming, app store, diagnostic/admin tools, easier setup than Linux, large support base.
• Weakness: costly/paid subscriptions; less secure than Linux/macOS; slows over time; frequent updates that sometimes fail.
• Competitive edge: Office and cloud products; Morningstar economic moat; three divisions: more personal computing, intelligent clouds, productivity and business processes.

macOS

• Created by: Apple (previously OS X).
• Versions: Mojave (2018), High Sierra (2017), Sierra (2016).
• Market share: less than 10%.
• Reason for lower share: Apple computers more expensive.
• Operability: more operable than Windows because proprietary (Apple makes both hardware and OS); consistent performance, security, support.
• Features: proprietary hardware; integrated system; iCloud connects Mac apps with iOS devices.
• Strength: fewer viruses than Windows; good customer support; consistent GUI; great speed/availability; long life; supports Windows file system and can run Windows.
• Weakness: most expensive; less software than Windows; poor gaming; no hardware customization; no cloud/server services like Windows/Linux.
• Competitive edge: security, ease of use, hardware-software harmony, superior hardware quality.

Linux

• Definition: family of open-source operating systems (can be modified/distributed by anyone).
• Market share: less than 2%.
• Servers: most servers run Linux because relatively easy to customize.
• Operability: faster than Windows; reduces bogging; Ext4 file system; no defragmentation support; privacy; built-in encryption; safer than Windows; open-source review of vulnerabilities; emphasizes uptime, process control, security.
• Components (7): boot loader, kernel, init system, daemons, graphical server, desktop environment, applications.
• Features: shows total memory used/cached/buffered/free; CPU time; stealing jobs; waiting for I/O; nice tasks; disk utilization; queuing; latency; throughput.
• Strength: fewer viruses/malware/slowdowns/crashes; open source; flexible; many versions; free distributions.
• Weakness: some device drivers unavailable; hardware makers prefer Windows/Mac; challenging for beginners; CLI learning curve; software hard to find; troubleshooting difficult; fewer experts; few software alternatives (Photoshop, Microsoft Office, games).
• Competitive edge: security, speed, cost, ease of maintenance; subscription-based pricing; no version upgrade fees; compact footprint; IBM server benefits.

Virtual memory

• Definition: technique allowing execution of processes not completely available in memory.
• Main advantage: programs can be larger than physical memory.
• Separates: user logical memory from physical memory.

Seven situations entire program not needed in main memory:

1. Error handling routines used only when error occurs
2. Rarely used options/features
3. Tables assigned fixed address space but only small part used
4. Partially in-memory execution counters many benefits
5. Less I/O to load/swap each user program
6. Program no longer constrained by physical memory amount
7. Each program takes less physical memory; more programs run; CPU utilization/throughput increase

• Figure 1.5 components: Virtual Memory (Page 0…n) → Memory Map → Physical Memory → Backing Store.
• Hard real-time: virtual memory almost never found.

Technical requirements

• Definition: implemented solutions professionals use to resolve technical problems/issues involving software; also called technical specifications or specs.
• Describe: technical aspects/issues to address for project/software to work successfully (performance, reliability, accessibility).
• Function as: solutions to technical issues.
• Why important: describe how software should function/behave; help developers/users understand use; proper implementation process; technical requirement documentation.
• Universal goal: ensure owners/developers understand future details and project estimations.
• Project estimations include: cost estimates, resource allocating, duration of development.

The 17 technical requirements (name + one key fact)

1. Accessibility — accessible to all users (e.g., closed captions)
2. Authentication and authorization — authentication = valid data; authorization = clearance
3. Availability — metric tracking time as percentage
4. Data quality — high-quality data for operations/decision-making
5. Human error — detects inaccurate input; notifies user
6. Information security — encryption of credentials/private info
7. Internal controls — data stewards access decryption keys only with higher official approval
8. Interoperability — works on all major OS, browsers, devices
9. Maintainability — resolve problems in set timeframe (most repairs in 1 hour)
10. Performance — load times should not exceed 2 seconds
11. Privacy — protects customer data from internal employees
12. Productivity — lets users be more productive (e.g., auto-generate data)
13. Reliability — average time between downtimes/failures
14. Serviceability — system must not completely shut down during upgrades
15. Standards — comply with security and architectural requirements
16. System errors — error code communicates discrepancy; documented in help database
17. Vendor lock-in — textbook: open-sourced, not proprietary, can be manipulated with custom code by any user

Boot methods

• USB: bootable USB created with programs; copy OS to flash drive; can update info; good for many computers.
• CD-ROM: Windows install media often on CD; computer needs built-in/external CD-ROM reader.
• DVD: similar to CD-ROM; needs DVD-ROM reader.
• PXE: Preboot Execution Environment; automatic installation from network drive; no physical media required.
• Mnemonic: U-C-D-P.

Installation types (8)

1. Creating image — clone existing OS; sector copies of everything
2. Unattended installation — uses unattend.xml; no installer present; common in large organizations
3. Upgrade — in-place; begins with previous OS present; keeps applications/files
4. Clean install — erases every file; requires backup; erases documents/settings
5. Repair installation — reinstalls OS files; no configuration/hard drive changes; for corrupted files/virus/Trojan
6. Multi boot (dual boot) — two OS on two distinct partitions; start-up prompt; e.g., Win 7 + Win 8
7. Remote network installation — no physical media; files on network drive; PXE; single centralized server
8. Image deployment — clone OS image to another PC; no installation program needed

Partitioning

• MBR (Master Boot Record): supports 4 partitions.
• GUID (Globally Unique Identifier): supports 128 partitions.
• Dynamic disk partition: can deny adding new drive; can span data from basic partition into new drive; supported by several Windows OS.
• Basic disk partition: Microsoft idea; has DOS or Windows installed; can bear primary and logical partitions with logical drives.

Numbers to memorize

Fact	Number
Module duration	40 hours
Windows market share	more than 80%
macOS market share	less than 10%
Linux market share	less than 2%
Boot methods	4
Installation types	8
Technical requirements	17
OS functions	16
Linux components	7
MBR partitions	4
GUID partitions	128
Performance load time	≤ 2 seconds
Maintainability repair time	1 hour
Virtual memory situations	7
Batch problems	3

Quick self-test (cover answers)

• OS loaded by? → boot program
• Traffic controller? → tracks process status
• I/O controller? → responsible for every device
• Hard real-time virtual memory? → almost never found
• macOS market share? → less than 10%
• Linux servers reason? → easy to customize
• Virtual memory advantage? → programs larger than physical memory
• Unattended install file? → unattend.xml
• PXE full name? → Preboot Execution Environment
• MBR partitions? → 4
• GUID partitions? → 128
• 17th technical requirement? → vendor lock-in (textbook: open-sourced)