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What is an operating system?
An interface between user applications and computer hardware to develop and execute programs.
What is the primary goal of an operating system?
Which of the following is a function of an operating system? (Select all that apply)
What type of operating system executes jobs one at a time?
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The secondary goal of an operating system is to provide an easy-to-use environment.
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What is a key characteristic of a multi-programmed/multi-tasking operating system?
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Which of the following statements best describes a real-time operating system?
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Which operating system type is characterized by resource sharing across multiple networked processors?
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What is the primary purpose of dual mode operations in an operating system?
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Which of the following is NOT typically a factor that influences the efficiency of an operating system?
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What is indicated by a mode bit value of 0?
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What does the fork() system call return to the parent process upon successful creation of a child process?
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Which of the following statements is true about process execution in user mode?
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What happens to the number of child processes created when 'n' fork() system calls are executed?
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Which of the following examples represents a non-privileged instruction typically allowed in user mode?
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Study Notes
What is an Operating System?
- An interface between user applications and computer hardware, facilitating program development and execution.
Goals of an Operating System
- Primary goal: Provide a user-friendly environment.
- Secondary goal: Efficient utilization of system resources.
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Other goals:
- Modularity
- Abstraction
- Ease of debugging
Functions of an Operating System
- Process Management
- Memory Management
- Resource Allocation
- File System Management
- Protection and Security
Types of Operating Systems
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Batch Operating System:
- Groups jobs with similar requirements into batches.
- Executes jobs sequentially on the CPU, one at a time.
- Issues: Increased CPU idleness and decreased system throughput.
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Multi-programmed/Multi-tasking Operating System:
- Allows multiple programs to reside in main memory for execution.
- The operating system selects and executes one of these programs on the CPU.
- If the job in execution needs an I/O operation, the operating system switches to another job.
- Benefits: Improved CPU utilization and faster overall system performance.
What is an Operating System?
- An operating system acts as an interface between user applications and computer hardware.
- It facilitates the development and execution of programs.
Goals of an Operating System
- Primary goal: Provide a user-friendly environment for users.
- Secondary goal: Ensure efficient utilization of computer resources.
- Operating systems are also known as resource allocators.
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Other goals:
- Modularity
- Abstraction
- Ease of debugging
Functions of an Operating System
- Process Management: Handles the creation, scheduling, and termination of processes.
- Memory Management: Manages the allocation and deallocation of memory to processes.
- Resource Allocation: Allots resources like CPU time, printers, and files to processes.
- File Systems Management: Organizes and manages files and directories on storage devices.
- Protection and Security: Protects the system and its resources from unauthorized access.
Types of Operating Systems
Batch Operating System
- Groups similar jobs together to execute on the CPU in batches.
- Jobs are executed sequentially, with one job completing before the next one starts.
- This can lead to increased CPU idleness and decreased system throughput.
Multi-programmed/ Multi-tasking Operating System
- Allows multiple jobs/programs to reside in main memory concurrently.
- The operating system selects and executes jobs on the CPU in a time-sharing manner.
- When a job requires I/O, the OS schedules another ready job onto the CPU.
- This significantly increases CPU utilization and system throughput.
- Multi-tasking is a logical extension of multi-programming, enabling multiple processes to share CPU time for better response times.
Real-time Operating System
- Characterized by strict time constraints for processing.
- Programs must be executed within defined time limits, otherwise, the system fails.
- Two categories: Hard real-time and Soft real-time.
- Critical for applications requiring immediate and predictable responses, like industrial control systems and medical devices.
Distributed Operating System
- Manages jobs executed by multiple processors interconnected through a network.
- Also referred to as loosely coupled systems.
- Advantages include:
- Resource sharing
- Faster computation speeds
- Improved reliability
Dual-Mode Operations
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Processors support two instruction execution modes:
- User mode/ Non-privileged mode: Restricted access to system resources.
- Kernel mode/ Privileged mode/ Monitor mode: Full access to hardware and machine instruction set.
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Purpose: Provide protection and security for both user applications and the OS from unauthorized users.
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The "mode bit" (0 for kernel mode, 1 for user mode) determines the execution mode of an instruction.
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Process in Kernel mode:
- Direct access to hardware.
- Full access to the machine instruction set.
- The operating system always operates in kernel mode.
- Examples of privileged instructions: I/O operations, context-switching, clearing the memory map.
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Process in User mode:
- No direct access to hardware.
- Limited access to the machine instruction set.
- Examples of non-privileged instructions: Reading the system clock, reading processor status, generating traps (interrupts).
System Calls
- System calls provide user applications with access to operating system services.
- They act as entry points into the kernel system.
Fork() System Call
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The
fork()system call is used to create child processes. -
Returns 0 to the newly created child process.
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Returns the process ID (PID) of the child process to the parent process upon successful creation.
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Returns a negative value to the parent process if child process creation fails.
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If a program has
nfork()system calls, the number of child processes created would be 2ⁿ - 1.
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Description
This quiz explores the fundamentals of Operating Systems, including their goals, functions, and various types. Understand the critical role an OS plays in facilitating user applications and managing system resources effectively.
