operating systems Flashcards
(28 cards)
What are the key services an operating system provides?
• User Interface (CLI, GUI, Batch)
• Program execution
• I/O operations
• File-system manipulation
• Communication
• Error detection
• Resource allocation
• Accounting
• Protection and Security
What types of user interfaces do operating systems typically offer?
• Command-Line Interface (CLI)
• Batch interface
• Graphical User Interface (GUI)
What is program execution in the context of OS services?
• The ability to load and run programs in memory
• Handle normal and abnormal termination
• Manage resources for execution
What does the operating system do in terms of I/O operations?
• Provides an interface to I/O devices
• Facilitates data exchange with files and peripherals
• Prevents direct device manipulation by users
How does an OS facilitate file-system manipulation?
• Allows creation, deletion, reading, and writing of files
• Manages directories and permissions
• Provides search and metadata access
Describe how OS handles communication between processes.
• Shared memory or message passing
• Inter-process or inter-system communication
• Handled via OS for data integrity and synchronization
What is error detection in operating systems?
• Identifying and handling hardware/software errors
• Includes power failure, memory issues, invalid instructions
• OS may terminate or recover processes
What is resource allocation in OS?
• Distribution of CPU time, memory, and I/O devices
• Done for concurrent users/processes
• May involve specific or general allocation algorithms
What is the role of the command interpreter or shell?
• Accepts user commands and executes them
• May be part of the kernel or user-level system program
• Examples include BASH, cmd.exe
How do batch files relate to OS?
• Scripts containing CLI commands
• Automate tasks
• Used in system diagnostics, automation, etc.
Describe the three major APIs for system calls.
• Win32 API (Windows)
• POSIX API (UNIX-based)
• Java API (Java VM)
How are system calls typically invoked?
• Programs use API functions
• System call number passed to OS kernel
• Kernel executes the call and returns status/result
What are some common types of system calls?
• Process control
• File manipulation
• Device management
• Information maintenance
• Communication
What are system programs?
• Utilities that provide a programming environment
• Examples: File managers, compilers, loaders, device drivers
What is a process in operating systems?
• A program in execution
• Needs resources like memory, CPU, files
• Can be user or system process
What is a process composed of?
• Text: Program code
• Stack: Temporary data
• Data: Global variables
• Heap: Dynamically allocated memory
What are the different states of a process?
• New
• Running
• Waiting
• Ready
• Terminated
What is the Process Control Block (PCB)?
• Data structure storing information about a process:
- Process state, program counter, CPU registers
- Scheduling info, memory info, I/O status
When is the PCB updated?
• Whenever a process changes state
• During interrupts, scheduling, or completion of tasks
What are the three major process scheduling queues?
• Job queue: All processes in system
• Ready queue: Processes in memory ready to execute
• Device queue: Processes waiting for I/O devices
What does the short-term scheduler do?
• Chooses next process to run
• Runs frequently (e.g., every few ms)
• Allocates CPU to processes
What is the role of the long-term scheduler?
• Decides which processes to bring into ready queue
• Runs less frequently
• Controls multiprogramming level
Differentiate between I/O-bound and CPU-bound processes.
• I/O-bound: More time in I/O, short CPU bursts
• CPU-bound: Long CPU usage, few I/O operations
Where does the operating system sit in the architecture?
Between system/application programs and computer hardware
