Operating System II: Advanced Features

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Questions and Answers

A computer system needs ______ to store data and instructions for processing.

memory

The access time between the CPU registers and the main memory is typically low.

False (B)

What are the two primary operations performed on memory?

  • Execute and Process
  • Read and Write (correct)
  • Store and Retrieve
  • Input and Output

What is the purpose of memory hierarchy design?

<p>To minimize access time.</p> Signup and view all the answers

Match the following memory concepts with their descriptions:

<p>Memory Management = Techniques for allocating and managing computer memory. Memory Hierarchy = A layered structure of memory with varying speeds and capacities. Virtual Memory = A technique that allows a computer system to use secondary storage as if it were main memory.</p> Signup and view all the answers

Which of the following is NOT a characteristic feature of the memory hierarchy?

<p>Frequency (E)</p> Signup and view all the answers

Cache memory is faster than main memory.

<p>True (A)</p> Signup and view all the answers

What are the two main types of memory within the memory hierarchy?

<p>Internal memory and External memory</p> Signup and view all the answers

The type of memory that stores data permanently is called ______ memory.

<p>non-volatile</p> Signup and view all the answers

Match the types of main memory with their respective characteristics:

<p>RAM = Read only, stores data permanently ROM = Read and write, stores data temporarily while working Volatile memory = Data is lost when power is turned off Non-volatile memory = Data is retained even when power is turned off</p> Signup and view all the answers

What is the purpose of using cache memory?

<p>To provide faster access to frequently used data (B)</p> Signup and view all the answers

Why is it important to have a memory hierarchy?

<p>To balance the trade-offs between speed, cost, and capacity of different types of memory.</p> Signup and view all the answers

The ______ is a memory storage mechanism that allows a computer to use more memory than it physically has.

<p>virtual memory</p> Signup and view all the answers

Which of the following is NOT a characteristic of Cache Memory?

<p>It is cheaper than main memory (A)</p> Signup and view all the answers

Secondary storage is typically faster and more expensive than main memory.

<p>False (B)</p> Signup and view all the answers

What is the main purpose of cache memory in a computer system?

<p>To reduce the access time for data and instructions used by the CPU.</p> Signup and view all the answers

Match the following memory types with their corresponding characteristics:

<p>Main Memory = Slower than cache memory, but faster than secondary memory Cache Memory = Stores data currently being executed or frequently accessed Secondary Memory = Permanent storage for data and programs Virtual Memory = Allows the computer to use more memory than physically available</p> Signup and view all the answers

Why is data from secondary storage first transferred to main memory before being processed by the CPU?

<p>The CPU can only directly access data stored in main memory (D)</p> Signup and view all the answers

The main memory stores data or instructions that are not currently being executed by the CPU.

<p>False (B)</p> Signup and view all the answers

What is the relationship between the CPU, main memory, and secondary storage in a computer system?

<p>The CPU processes data stored in main memory. Data is transferred from secondary storage to main memory before being processed by the CPU, and back to secondary storage for long-term storage.</p> Signup and view all the answers

The speed at which the CPU can execute instructions is affected by the ______ time.

<p>access</p> Signup and view all the answers

A technique where only necessary parts of processes are loaded from secondary storage into main memory is called ______.

<p>paging</p> Signup and view all the answers

The primary goal of the OS protection is to ensure proper data backup and recovery in case of system failure.

<p>False (B)</p> Signup and view all the answers

What fundamental principle is used to minimize potential harm from system errors or malicious actions?

<p>Principle of least privilege (B)</p> Signup and view all the answers

Match the following protection principles with their respective descriptions:

<p>Principle of least privilege = Users are given only the minimum permissions required to perform their tasks. Principle of separation of concerns = Dividing system functionalities into distinct, independent modules. Principle of data integrity = Ensuring that data remains accurate and consistent throughout its lifecycle. Principle of modularity = Building systems with loosely coupled, independent components. Principle of security = Protecting system resources from unauthorized access and modification. Principle of integrity = Preserving the accuracy and reliability of data. Principle of availability = Ensuring that resources are accessible to authorized users when needed.</p> Signup and view all the answers

Explain what is meant by "the principle of least privilege" in the context of operating systems.

<p>The principle of least privilege suggests that users or processes should be granted only the minimum privileges necessary to perform their assigned tasks. This helps to minimize potential harm caused by errors or malicious actions, as restricted access limits the impact of any unauthorized behavior.</p> Signup and view all the answers

What is one of the main goals of the OS protection mechanism?

<p>To prevent erroneous programs from accessing unauthorized resources. (A)</p> Signup and view all the answers

The ______ is a data structure used to represent the permissions of objects and subjects in an operating system.

<p>access matrix</p> Signup and view all the answers

File permissions control the access to individual files but not directories.

<p>False (B)</p> Signup and view all the answers

Briefly describe how file permissions work to control access to system resources.

<p>File permissions are settings assigned to files and directories that determine which users or groups can access them and what actions they can perform (e.g., read, write, execute). These permissions are typically set by the file owner or system administrator and provide a robust mechanism for controlling access to sensitive data and resources.</p> Signup and view all the answers

What is the primary goal of the OS protection mechanism?

<p>To prevent unauthorized access to system resources. (B)</p> Signup and view all the answers

Which of these is NOT a main goal of OS protection?

<p>Protect the system from administrators and users. (C)</p> Signup and view all the answers

Which of the following principles is used to minimize potential harm from system errors or malicious actions?

<p>Principle of least privilege (D)</p> Signup and view all the answers

What does the "principle of least privilege" mean in the context of operating systems?

<p>Users and systems are given the minimum number of privileges needed to perform their tasks. (B)</p> Signup and view all the answers

When is a part of secondary storage treated as main memory?

<p>When the CPU needs to access data that is not in main memory. (A)</p> Signup and view all the answers

What is the technique called where only the required parts of processes are loaded from secondary storage into main memory?

<p>Virtual Memory (B)</p> Signup and view all the answers

What is the data structure used to represent the permissions of objects and subjects in an operating system?

<p>Access Control List (B)</p> Signup and view all the answers

What control mechanism used by the OS allows a user to run an executable file?

<p>File Permissions (B)</p> Signup and view all the answers

Which of the following is NOT a principle of protection used in operating systems?

<p>Principle of user authentication (B)</p> Signup and view all the answers

What are the main access control mechanisms used by an OS, as discussed in the content?

<p>File Permissions and Access Matrix (D)</p> Signup and view all the answers

What are Trojan Horses primarily known for?

<p>Serving as a security trap for user credentials (C)</p> Signup and view all the answers

What characteristic defines a Logic Bomb?

<p>Requires specific conditions to activate (A)</p> Signup and view all the answers

What is the main function of a Worm in the context of system threats?

<p>Generating multiple copies to overwhelm system resources (B)</p> Signup and view all the answers

Which of the following best describes Denial of Service attacks?

<p>They prevent legitimate users from accessing network resources (C)</p> Signup and view all the answers

What does the term 'Trap Door' refer to in computer security?

<p>A hidden vulnerability exploited by attackers (C)</p> Signup and view all the answers

What is the primary purpose of memory management in an operating system?

<p>To manage data storage and retrieval efficiently. (C)</p> Signup and view all the answers

Which of the following best defines virtual memory?

<p>A technique that allows running applications without sufficient physical memory. (D)</p> Signup and view all the answers

What is the function of the memory hierarchy in a computer system?

<p>To minimize the time required for data access. (A)</p> Signup and view all the answers

Which type of memory holds data in binary format for processing tasks?

<p>Physical memory (B)</p> Signup and view all the answers

What is a significant drawback of having high access time between the CPU and main memory?

<p>It slows down the overall processing speed. (D)</p> Signup and view all the answers

Which address type refers to the actual location in memory hardware?

<p>Physical address (A)</p> Signup and view all the answers

What is a characteristic feature of cache memory?

<p>It has a low access time. (B)</p> Signup and view all the answers

Which type of memory is considered volatile?

<p>Random Access Memory (RAM) (B)</p> Signup and view all the answers

What is the primary role of secondary memory in the memory hierarchy?

<p>To store data permanently. (A)</p> Signup and view all the answers

How is virtual memory different from other types of memory?

<p>It allows the use of more memory than is physically available. (D)</p> Signup and view all the answers

Which of the following is true about primary memory?

<p>It offers fast access times for currently used data. (D)</p> Signup and view all the answers

What distinguishes RAM from ROM?

<p>RAM is volatile while ROM is non-volatile. (C)</p> Signup and view all the answers

Which level of memory is directly accessible by the processor?

<p>Primary Memory (A)</p> Signup and view all the answers

Why is cache memory vital for system performance?

<p>It reduces the access time for frequently used data. (C)</p> Signup and view all the answers

What is a Man-in-the-middle attack?

<p>An attack that imitates both ends of a communication conversation. (C)</p> Signup and view all the answers

Which of the following is NOT a method of security violation?

<p>Data encryption (B)</p> Signup and view all the answers

What is the main function of ROM in the memory hierarchy?

<p>To store critical system firmware permanently. (D)</p> Signup and view all the answers

What type of attack deliberately overwhelms a network to prevent legitimate access?

<p>Denial of service (C)</p> Signup and view all the answers

Which security level focuses on protecting physical infrastructure?

<p>Physical security (A)</p> Signup and view all the answers

What is dumpster diving in the context of security attacks?

<p>Searching trash for sensitive information. (B)</p> Signup and view all the answers

Which of the following threats involves an attacker impersonating a legitimate user?

<p>Session hijacking (A)</p> Signup and view all the answers

What type of attack seeks to exploit personal data gleaned from email or social networks?

<p>Phishing (C)</p> Signup and view all the answers

Which of the following best describes a replay attack?

<p>Repeating valid data transmissions to gain access. (C)</p> Signup and view all the answers

What type of attack focuses on exploiting weaknesses in software to bypass authentication?

<p>Session hijacking (C)</p> Signup and view all the answers

Which of the following is a method to gain unauthorized access by breaking passwords?

<p>Password cracking (D)</p> Signup and view all the answers

Flashcards

Memory Management

The process of handling memory usage in a computer system to store data and instructions efficiently.

Virtual Memory Management

A technique that uses disk space to extend the apparent available memory of a computer system.

Symbolic Memory Address

An abstract representation used by programs to access memory locations, typically a name or label.

Physical Memory Address

The actual hardware address in memory where data is stored, as seen by the computer's hardware.

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Memory Hierarchy

A structured arrangement of different types of memory, optimized to minimize access time.

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Cache Memory

A small, fast memory located inside the CPU that stores frequently accessed data.

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Purpose of Cache Memory

To decrease access time and speed up CPU execution.

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Main Memory

Primary storage that loads programs and data for processing by the CPU.

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Secondary Memory

Long-term storage that retains data permanently, but is slower than main memory.

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Virtual Memory

A memory storage mechanism that allows a computer to use hard drive space as additional RAM.

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Data Transfer Process

Data from secondary storage is transferred to main memory before being processed.

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Characteristics of Cache Memory

Faster access, expensive, limited capacity, stores frequently accessed data.

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Non-volatile Memory

Memory that retains data without power, like secondary memory.

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Examples of Secondary Memory

Includes SSDs, HDDs, CDs/DVDs, and USB drives.

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Paging

The process of loading only required pages from secondary memory into main memory for execution.

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Segmentation

A memory management technique that divides processes into segments, which can be loaded into memory as needed.

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Protection Goals

The main objectives to ensure the integrity and availability of shared resources in an OS.

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Principle of Least Privilege

A security principle stating that users and systems should have the minimum privileges necessary to perform their tasks.

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Access Control Mechanisms

Methods used by an OS to control access to its resources and to protect information.

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Access Matrix

A table that defines permissions for users and system entities regarding various resources in an OS.

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File Permissions

Settings that control who can read, write, or execute files and directories in an OS.

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Error Recovery

Mechanisms within an OS that help to recover from erroneous programs or system failures.

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Internal Memory

Also known as primary memory, it consists of memory directly accessible by the CPU.

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External Memory

Also referred to as secondary memory, it is accessed by the processor through I/O modules.

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RAM

Random Access Memory, a type of volatile memory used for temporary data storage while working.

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ROM

Read Only Memory, a type of non-volatile memory used for permanent data storage.

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Volatile vs Non-Volatile

Volatile memory loses data when power is off; non-volatile retains data without power.

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Memory Hierarchy Level

Different levels of memory defined by response time, complexity, cost, and capacity.

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Types of Memory

Memory types are categorized as internal (primary) and external (secondary) memory.

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Main Memory vs Secondary Memory

Main memory is temporary storage accessible by the CPU; secondary memory is long-term storage.

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Volatile Memory

Type of memory (e.g., RAM) that loses its data when power is turned off.

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Cache Memory Purpose

Designed to decrease access time to data by storing frequently accessed information.

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Program Threats

Malicious tasks performed by user programs on systems.

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Trojan Horse

A program that misleads users by pretending to be a legitimate application.

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Logic Bomb

A program that activates destructive actions under specified conditions.

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Denial of Service

An attack preventing users from accessing legitimate network services.

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When to use virtual memory?

When processes need more storage than available main memory.

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Technique for memory management

Loading only required pages from secondary memory to main memory for execution.

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Goals of Protection in OS

To ensure integrity and availability of shared resources and protect against erroneous programs.

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Access Matrix Purpose

Defines permissions for users regarding various resources in an OS.

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Segmentation Technique

Divides processes into segments for loading them as needed.

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Paging Functionality

Loads specific pages from secondary memory into main memory for execution.

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Erroneous Program Recovery

Mechanisms in an OS that help recover from system failures caused by errors.

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Memory Purpose

Memory is used to store data and instructions for processing in a computer system.

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Binary Data Storage

Data in a memory is stored as binaries, represented by 0's and 1's.

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Memory Operations

The two main operations of memory are Read and Write.

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Access Time

The time it takes for the CPU to access data from memory.

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High Access Time

The delay in data access between CPU registers and main memory was significant.

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Memory Hierarchy Design

A structure designed to minimize access time by organizing different memory types.

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Memory Management Skills

The ability to handle and optimize memory usage in a computer.

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Man-in-the-middle attack

An attack where the attacker secretly intercepts and relays messages between two parties.

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Replay attack

A malicious act of capturing valid data transmissions and retransmitting them.

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Session hijacking

An attack where the attacker takes over a session between two parties to steal information.

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Phishing

A method of tricking individuals into providing sensitive information through deceptive emails or websites.

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Denial of Service (DoS)

A cyber attack meant to make a computer or network resource unavailable to its intended users.

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Password Cracking

The process of attempting to gain unauthorized access to a system by guessing or using software to brute-force passwords.

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Dumpster Diving

Searching for discarded documents or electronic files that contain sensitive information.

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Memory-access violations

Errors that occur when a program attempts to access memory that it's not allowed to.

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Operating System Threats

Potential vulnerabilities and attack techniques that target the OS’s processes and operations.

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Wireless Communication Threats

Security risks associated with wireless technology that can expose information to unauthorized parties.

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Study Notes

Chapter 1: Operating System II, Section 1: Advanced Features of OS

  • This section covers advanced features of operating systems.
  • The objectives are to illustrate memory management, virtual memory management techniques, and define symbolic and physical memory addresses.

Keywords

  • Memory hierarchy: A hierarchical arrangement of computer storage based on access time, cost, capacity, and access mode.
  • Cache memory: A very fast, expensive memory type that acts as a buffer between main memory (RAM) and the CPU.
  • Virtual memory: A storage mechanism that allows a part of secondary memory to be used as primary memory.
  • Virtual Memory Management (VMM): Manages the extra storage needed for a program in the main memory.
  • Memory Manager Unit (MMU): Hardware that maps logical addresses to physical addresses in main memory.

Memory Management

  • Computer systems use memory to store data and instructions for processing.
  • Data is stored in binary format (0s and 1s).
  • The table shows the units of measurement for digital data (bits, bytes, kilobytes, etc.).

Memory Hierarchy

  • The operations of memory are read and write.
  • Access mode: How easily the memory can retrieve the required information.
  • Access time: The average time to reach a storage location.
  • Transfer rate: The number of characters/words a device can transfer per second.
  • Capacity: The maximum data that can be stored.
  • Memory hierarchy minimizes access time for different memory levels based on factors like response/access time, complexity, cost, and capacity.
  • Memory hierarchy differentiates in each level based on the factors: response/access time, complexity, cost, capacity.
  • Levels (from top to bottom of the hierarchy): CPU registers, cache memory, main memory, magnetic disk, optical disk, and magnetic tape.
  • Internal memory: Accessible by the processor (RAM, main memory, cache).
  • External memory: Accessible through an I/O module (magnetic disk, optical disk, magnetic tape).
  • RAM: Random Access Memory (main memory), used for reading and writing (volatile).
  • ROM: Read-Only Memory, used for read-only operations (non-volatile).

Cache Memory

  • Cache memory is inside the CPU.
  • Decreases access time.
  • Faster than main memory.
  • Expensive.
  • Limited capacity.
  • Stores data being executed or frequently accessed within a short time period.

Secondary Memory

  • Secondary memory has high storage capacity.
  • Examples: SSD, HDD, USB Drives, memory cards, optical disks, magnetic tape

Virtual Memory

  • A memory storage mechanism.
  • Used when a user needs more storage than available main memory. A part of secondary storage is treated as main memory.
  • The technique involves paging and segmentation

Access Control

  • A security technique to regulate who can access resources in a computing environment.
  • Physical Access Control: Limits access to physical locations (e.g., data centers, servers).
  • Logical Access Control: Limits access to computer systems (e.g., network, files, data).

Security and Protection

  • Deals with protecting systems from deliberate attacks (internal or external).
  • Includes protecting data and resources.
  • Common attacks: physical attacks (phishing, dumpster diving), software attacks that target the operating system (password cracking), network attacks (denial of service attacks, wireless communication hacking, memory access violations, data center attacks).

Program Threats

  • Malicious tasks performed by user programs are called program threats.
  • Example threats: Trojan horse, trap door, logic bomb, virus

System Threats

  • Misuse of system services and network connections for malicious purposes.
  • System threats include worms, port scanning, denial of service attacks.
  • Additional threats like denial of service, phishing, dumpster diving, password cracking, and network-related issues (e.g., wireless communication attacks, memory access violations).

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