Operating Systems - Unit 05

Operating Systems - Unit 05

• Operating System Classification:

  • Single user - single task: One user, one task at a time.
  • Single user - multi-task: One user, multiple tasks simultaneously.
  • Multi-user - multi-task: Multiple users, multiple tasks simultaneously.
  • Multi-threading: Improves application performance by allowing parallel execution of sub-processes.
  • Real-time: Designed for highly reliable applications requiring precise timing, crucial in safety-critical situations.
  • Time-sharing: Enables multiple programs/users to share the processor (CPU) time, ensuring fast response times and reducing CPU idleness.
  • Multiprogramming: Allows multiple programs to be loaded into memory and executed concurrently by sharing CPU time.
  • Multitasking: Enables concurrent execution of multiple tasks.

• File Systems:

  • FAT (File Allocation Table): Supports various devices and includes features like encryption, recovery, and compression.
  • NTFS (New Technology File System): Supports advanced features such as encryption, recovery, and compression.
  • Fragmentation (Internal/External): Issues that arise when allocated disk space is not completely contiguous for the file. Internal fragmentation is when the allocated space has unused portions, and external fragmentation is when sufficient contiguous space exists but isn't available.

• Storage Allocation:

  • Contiguous Allocation: Allocates disk space in contiguous blocks, simple but susceptible to fragmentation and doesn't easily extend files.
  • Linked Allocation: Each block in a file points to the next, allowing easy file growth but requiring multiple seeks to access the file.
  • Indexed Allocation: Uses a table of pointers (index block) for fast access, eliminating external fragmentation.

• Disk Formatting:

  • Low-level Formatting: Low-level formatting physically marks the cylinders and tracks of a hard disk.
  • Partitioning: Divides the hard disk into regions (partitions) for better organization and management.
  • High-level Formatting: Creates and configures a file system on a hard disk partition.

• Process Management:

  • Process Control Block (PCB): A data structure maintained by the OS for each process, containing essential information like Process ID (PID), state, CPU registers, I/O status, and memory management details.
  • Process States: Processes go through different states (new, ready, running, wait/blocked, terminated, suspend/wait, suspend/ready) during execution.

• Scheduling Policies:

  • Non-preemptive: A running process continues until it terminates, blocks, or changes to another state.
  • Preemptive: A running process may be interrupted by the OS for certain reasons, like timing or priority.

• Context Switching:

  • Used by the OS to switch between processes.

• Interrupts: Events that cause a change in the order of process execution.

• Process Scheduling:

  • Long-term Scheduling (Job Scheduling): Controls the process rate admitted into the system.
  • Medium-term Scheduling: Handles swapping of processes between memory and storage when needed.
  • Short-term Scheduling (CPU Scheduling): Selects and allocates the CPU to a ready process.

• Times Related (Processes):

  • Waiting Time: Time a process waits in a queue to get the CPU.
  • Arrival Time: When a process enters the ready queue.
  • Burst Time: Time needed to execute a process in the CPU.
  • Completion Time: Time a process finishes.
  • Turnaround Time: Total time from submission to completion of a process.
  • Response Time: Time taken between arrival and obtaining the CPU.
  • Throughput: Number of processes completed in a unit of time.

Memory Management

• Memory Management Unit (MMU): Converts virtual addresses to physical addresses.
• Paging: Divides memory into fixed-size blocks (pages) for efficient allocation and management.
• Logical Address: Address of a data element as seen by a program.
• Physical Address: Actual address in RAM.
• Page Table: A table that maps virtual pages to physical frames.
• Virtual Memory: Allows running programs larger than available physical memory, using secondary storage for parts.
• Page Fault: An event when a program tries to access a page not in RAM, requiring retrieval from secondary storage.

Device Management

• Spooling: A technique to buffer I/O operations to improve performance.
• Buffering: A technique to store data temporarily before processing or transferring.
• Caching: A fast access storage to reduce access time.
• Device Drivers: Software that enables interaction between the computer and peripheral devices.

Explore the key concepts of operating systems in Unit 05, including classifications such as single user and multi-user systems, multitasking, and real-time operations. Additionally, gain insights into various file systems like FAT and their functionalities. Test your knowledge and comprehension of these vital topics within operating systems.