Operating System II PDF

Chapter 1: Operating System II Section 1: Advanced features of OS Academic year: 2024-2025 Objectives Illustrate the purpose of memory management. Illustrate the virtual memory management technique. Define symbolic and physical memory addresses....

Chapter 1: Operating System II Section 1: Advanced features of OS Academic year: 2024-2025 Objectives Illustrate the purpose of memory management. Illustrate the virtual memory management technique. Define symbolic and physical memory addresses. 2 Keywords 3  Memory Management  A computer system needs memory to store data and instructions for processing.  A computer system data is stored as binaries (0's and 1's) in the memory. 4  Memory Hierarchy  The operations of the memory are Read and Write. 5  Memory Hierarchy  The access time between the CPU registers and the main memory was high.  Memory hierarchy design  minimizes the access time. Memory hierarchy differentiates in each level based on response/access complexity cost capacity time 6 Memory Hierarchy Memory Hierarchy Design types Internal External Memory or Memory or Primary Secondary Memory Memory accessible by Accessible by the processor Consist of Consist of the processor through I/O module cache 7 magnetic main memory CPU registers magnetic disk optical disk memory tape 8 Memory Hierarchy 9 Characteristic Features of Memory Systems Memory system Main Cache Secondary Virtual Memory memory memory memory 10 Characteristic Features of Memory Systems Memory system Main Cache Secondary Virtual Memory memory memory memory Known as Fast , Less Limited “Primary access Types capacity memory” time 11 RAM ROM Systems Characteristic Features of Memory Main memory types RAM ROM Name Random Access Memory Read Only Memory Function Read and write Read only Storing Type Storing temporarily while Storing permanently working Memory type 12 volatile memory (unsaved non-volatile memory work is lost) Characteristic Features of Memory Systems Memory system Main Cache Secondary Virtual Memory memory memory memory 13 14  Characteristic Features of Memory Systems  Why cache memory? Main memory loads the Processer in the CPU The program you data of the program will process the data opened 15  Characteristic Features of Memory Systems  Why cache memory? More data CPU execution Data from speed secondary storage Main memory loads Processor in CPU The program transferred first to the data of the will process the you opened main memory program data Characteristic Features of Memory Systems Cache memory is inside CPU but Main memory comes before the processor. Cache memory Decreases the access time Faster than the main memory Expensive Capacity is limited Store the data currently being executed or frequently accessed temporary data or data which may be executed within a short period 17 of time Characteristic Features of Memory Systems Memory system Cache Secondary Virtual Main Memory memory memory memory Permanently Slower and store the High storage cheaper than non-volatile Examples data or capacity the main instructions memory SSD Hard HDD (Hard USB flash Memory card CD / DVD Drive Desk Drive) drive 18  Characteristic Features of Memory Systems Data from Processor in CPU Main memory loads The program secondary storage will process the the data of the you opened transferred first to data program main memory 19 Characteristic Features of Memory Systems Memory system Main Cache Secondary Virtual Memory memory memory memory 20 Virtual Memory Definition A memory storage mechanism. When is it used? When a user works on processes that require more storage than the available main memory, a part of secondary storage will be treated as the main memory. 21 What is the technique? only required pages or parts of processes are loaded from the secondary memory into the main memory for execution and that is done by paging and segmentation system 22 Chapter 1: Operating System II Section 1: Advanced features of OS Academic year: 2024-2025 25 Objectives Construct two access control mechanisms used by an OS. Use protection and security principles in OS. 26 Keywords 27 Security and Protection  Protection - Goals of protection The shared resource Main goals of OS protection are to ensure Erroneous programs that: Administrators and users 28 Security and Protection  Protection - Principles of protection To protect the OS, we use principle of protection. What “principle of least privilege” means? Principle of least privilege users and systems are given enough privileges to perform their tasks. Therefore, in case of any failures least harm is done to the system. 29 Security and Protection  Protection – Access Matrix 30 Security and Protection  Protection – File Permissions Operating systems control file access by setting permissions for files and directories. allows a user to run an executable file. allows a user to open Certain files are allows a user to open allows a user to the file or directory, executable files, and read a file or delete the file or make changes, and usually directory directory save those changes ending in.exe or.com  Security and Protection  Protection – Access Control Definition A security technique that regulates who can view or use resources in a computing environment. Limit access to campus, Physical Access Control rooms, buildings and physical IT assets Access control types Limits connection to Logical Access Control computer network, system files and data  Security and Protection  Security Security deals with protecting systems from deliberate attacks, These attacks intentionally attempting to either internal or external. deliberately cause damage steal information disturbances to the information organization  Security and Protection  Security - Security violation methods Methods Attacker Man-in-the-middle Replay attack Session hijacking pretending attack The attacker attacker imitates The attackers capture pretend to be an Repeating a valid both ends of the an already-established authorized user to transmission conversation to session to bypass authentication, escalate privileges two targets  Security and Protection  Security - Standard security attacks Levels to protect the system Operating Physical Human Network System  Security and Protection  Security - Standard security attacks Levels to protect the system Operating Physical Human Network System Physical Data centers servers component  Security and Protection  Security - Standard security attacks Levels to protect the system Physical Human Operating System Network Phishing Dumpster Diving Password Cracking  Security and Protection  Security - Standard security attacks Levels to protect the system Operating Physical Human Network System denial of memory-access service violations  Security and Protection  Security - Standard security attacks Levels to protect the system Operating Physical Human Network System wireless portable communicatio devices ns  Security and Protection  Security – Program Threats o The operating system's processes do the designated task as instructed. o If a user program made these processes do malicious tasks, then it is known as Program Threats. Program threats Trojan Horse Trap Door Logic Bomb Virus program replicate themselves program has a on the computer traps user login misbehaves only security hole in its system. They are credentials and when certain code and performs highly dangerous and stores them conditions are met can modify/delete user illegal action (hard to predict) files, crash systems  Security and Protection  Security – System Threats Definition Is the misuse of system services and network connections. System threats Port Denial Worm scannin of g service Process that a mechanism by Denial of service Prevents other generates multiple which a hacker can attacks prevent users processes from Can shut down the copies each copy detect system from making getting the required network uses system vulnerabilities to legitimate use of the resources. resources make an attack system Create poster  System threats Port Denial Worm scannin of g service a mechanism by Denial of service Process that Prevents other which a hacker attacks prevent generates processes from Can shut down can detect users from multiple copies getting the the network system making each copy uses required vulnerabilities to legitimate use of system resources resources. make an attack the system Levels to protect the system Levels to protect the system Physical Human Operating System Network Operating Physical Human Network System Phishing Dumpster Diving Password Cracking