Muhammad Sufiyan

  SDLC Models in Detail: 1. Waterfall Model: - This is the basic/classic SDLC model - The phases happen in a strict linear sequence - requirements, design, implementation, testing, deployment, maintenance - Each phase must be completed fully before moving to the next phase - It is like a "waterfall" of progress flowing steadily downwards - Easy to understand and use, but very rigid and no room for revisions once a phase is over 2. Iterative Waterfall Model:  - Provides a feedback path to previous phases to allow changes/revisions - For example, if an issue is found in testing, you can loop back and rework the design - More flexible than the basic waterfall, but still quite rigid and sequential 3. Incremental Model: - The product is built and delivered in incremental releases - For example, an email app may release basic emailing first, then add calendaring, contacts, etc. in later increments   - Each increment goes through the full SDLC cycles - Allows faster delivery of core

A2 Q-1. **Advantages and disadvantages of threads compared to processes:**    - *Advantages*: Threads share resources, such as memory, more efficiently than processes. They are lighter-weight, as they share the same address space, which reduces overhead. Threads can communicate more easily since they share memory.    - *Disadvantages*: Threads can lead to synchronization issues, such as race conditions and deadlocks. They are also harder to debug due to shared memory. Q-2. **Priority scheduling:**    - Priority scheduling assigns priorities to tasks, with higher-priority tasks being executed first. Potential drawbacks include the possibility of starvation for lower-priority tasks and the potential for priority inversion.    - Drawbacks can be mitigated by implementing techniques such as aging (increasing the priority of tasks over time) and priority boosting (temporarily raising the priority of certain tasks). Q-3. **First Come First Served (FCFS) scheduling:**    - FCFS scheduling is

1. **Synchronization Hardware:**    - Imagine you have a group project where each team member needs to work on a specific part simultaneously. Synchronization hardware ensures that everyone knows when to start and finish their task, preventing chaos and ensuring smooth collaboration. 2. **Atomic Operations:**    - Think of atomic operations as a "do not disturb" sign on a door when someone is inside doing something important. It guarantees that either the entire task is completed successfully, or none of it happens at all, avoiding halfway-done tasks and maintaining consistency. 3. **Memory Barriers and Fences:**    - Picture a bulletin board where everyone posts updates and announcements. Memory barriers and fences act like moderators, making sure that everyone sees the updates in the correct order and preventing misunderstandings or outdated information. 4. **Cache Coherence Protocols:**    - Imagine you and your friends have copies of the same book to study. Cache coherenc

 Certainly, let's explain each CPU scheduling algorithm in a more formal manner: ### First Come, First Served (FCFS) - **Description**: FCFS is a non-preemptive CPU scheduling algorithm where processes are executed in the order they arrive in the ready queue. - **Operation**: Upon arrival, processes are added to the end of the ready queue. The CPU is allocated to the first process in the queue, which continues execution until it completes its CPU burst or enters an I/O wait state. Subsequent processes are selected for execution based on their arrival order. - **Characteristics**:   - **Advantages**: Simple implementation, fair execution order.   - **Disadvantages**: Potential for poor response time and inefficient CPU utilization, especially with long-running processes. ### Shortest Job First (SJF) - **Description**: SJF is a CPU scheduling algorithm that selects the process with the shortest expected CPU burst time for execution. - **Operation**: Processes are selected for executi

### CPU Scheduling Overview: Imagine you're a teacher assigning tasks to your students during class time. Your goal is to make sure everyone gets a fair chance to contribute while keeping the class productive and engaged. ### CPU Scheduling Functions: 1. **Process Management:** This is like managing a queue of tasks. You decide which student (process) gets to speak (execute) next.     2. **Resource Allocation:** You ensure each student (process) gets a fair share of speaking time (CPU time).     3. **Performance Optimization:** You aim to keep the class running smoothly by minimizing disruptions (context switches) and maximizing participation (CPU utilization). ### CPU Scheduling Operation: You manage the class by: 1. **Process Arrival:** When a student is ready to speak, they join the queue.     2. **Scheduling Decision:** You choose which student speaks next based on various factors like importance (priority) or task difficulty (CPU burst time).     3. **CPU Execution:** The chos

1. **Threads:**    - Definition: Threads are the smallest sequence of programmed instructions that can be managed independently by a scheduler within a process. They share the same memory space, allowing them to execute concurrently.    - Benefits:      - Concurrency: Enables multiple tasks to run concurrently within a single process, improving performance and responsiveness.      - Resource Sharing: Threads within the same process share resources, making communication and data sharing faster.      - Lightweight: Threads are faster to create and switch between compared to processes since they share resources within the same process. 2. **Types of Threads:**    - User Threads: Managed entirely by a user-level thread library, not visible to the operating system.    - Kernel Threads: Managed by the operating system kernel, visible to the scheduler. 3. **Thread States:**    - Common states: running, ready, blocked, or terminated. The scheduler manages state transitions and determines which

Let's break down and simplify the key topics from the lecture: ### Process Concepts - **Process**: In a multitasking system, a task or job is submitted as a process. Operating systems handle multiple processes on a single processor, allowing for multitasking behavior. - **Abstraction**: An operating system represents hardware resources as abstractions, hiding unnecessary details from users and programmers. - **Process as a Unit**: A process is an abstract model of a sequential program in execution, which the operating system can schedule as a unit of work. ### Process Control Blocks (PCB) - **Definition**: PCB is a data structure that holds all information about a process, created by the operating system to manage processes. - **Contents**: PCB includes process name, priority, state, hardware state, scheduling info, memory management info, I/O status, file management info, and accounting info. - **Purpose**: PCB helps the operating system manage and track processes during their lif

 Operating System Services: 1. **Program Execution**:    - The OS provides an environment for users to conveniently run programs.    - Handles memory allocation, CPU scheduling, etc., so users don't need to worry about them.     2. **I/O Operations**:    - OS hides hardware details for Input/Output (I/O) operations, making it easier for users.    - Ensures efficient and protected I/O operations, not controlled by user-level programs.     3. **File System Manipulation**:    - OS manages reading/writing to files, relieving users from secondary storage management.    - Simplifies tasks for user programs by handling file operations.     4. **Communications**:    - OS facilitates communication between processes, whether on the same or different computers.    - Relieves users from managing message passing between processes.     5. **Error Detection**:    - Constantly monitors the system to detect errors, preventing system-wide malfunctions.    - Relieves users from worrying about errors