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What are the major high-level components of a computer system according to the document?
What are the major high-level components of a computer system according to the document?
Hardware, Operating system, Applications programs, Users
What are some of the main issues involved in executing executable programs on a computer system?
What are some of the main issues involved in executing executable programs on a computer system?
An operating system serves as an intermediary between a user and computer hardware.
An operating system serves as an intermediary between a user and computer hardware.
True
In a single-user system, a computer system that allows only 1 user to use the computer at a given time.
In a single-user system, a computer system that allows only 1 user to use the computer at a given time.
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Match the following system types with their descriptions:
Match the following system types with their descriptions:
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What type of systems are executed in a 'batch' one after the other?
What type of systems are executed in a 'batch' one after the other?
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In a batch system, the CPU is often idle due to mechanical I/O devices being slower than electronic devices.
In a batch system, the CPU is often idle due to mechanical I/O devices being slower than electronic devices.
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What is the major task of an operating system in a batch system?
What is the major task of an operating system in a batch system?
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Multi-programming increases CPU utilization by organizing jobs so that the CPU always has one to ______.
Multi-programming increases CPU utilization by organizing jobs so that the CPU always has one to ______.
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Match the following system types with their descriptions:
Match the following system types with their descriptions:
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What is the purpose of the base register in memory protection?
What is the purpose of the base register in memory protection?
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What are some responsibilities of an operating system in memory management?
What are some responsibilities of an operating system in memory management?
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A timer is used in CPU protection to prevent a program from running too short.
A timer is used in CPU protection to prevent a program from running too short.
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A _______ interrupt is generated that transfers control from the current process to the next scheduled process.
A _______ interrupt is generated that transfers control from the current process to the next scheduled process.
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What are the four events that cause execution of a piece of code in the kernel?
What are the four events that cause execution of a piece of code in the kernel?
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What are system calls?
What are system calls?
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The bottom layer in a typical OS layered structure is ____________.
The bottom layer in a typical OS layered structure is ____________.
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Match the following categories with their descriptions:
Match the following categories with their descriptions:
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The microkernel approach removes all non-essential components from the kernel.
The microkernel approach removes all non-essential components from the kernel.
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What is the significance of the root directory in a Linux file system?
What is the significance of the root directory in a Linux file system?
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Which command is used to display the contents of a directory in Linux?
Which command is used to display the contents of a directory in Linux?
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Hidden files in Linux are also known as dot files.
Hidden files in Linux are also known as dot files.
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In Linux, the ________ directory stores system boot files including the kernel image.
In Linux, the ________ directory stores system boot files including the kernel image.
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Match the Linux directory with its purpose:
Match the Linux directory with its purpose:
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What is the primary role of the short-term scheduler in an operating system?
What is the primary role of the short-term scheduler in an operating system?
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Why must the short-term scheduler be fast?
Why must the short-term scheduler be fast?
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What is the primary role of the long-term scheduler?
What is the primary role of the long-term scheduler?
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The long-term scheduler executes more frequently than the short-term scheduler.
The long-term scheduler executes more frequently than the short-term scheduler.
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A medium-term scheduler may remove processes from memory to reduce the ____________.
A medium-term scheduler may remove processes from memory to reduce the ____________.
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What is the command to display the absolute pathname of your working directory?
What is the command to display the absolute pathname of your working directory?
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Which command is used to copy a file named file1 to another file named file2?
Which command is used to copy a file named file1 to another file named file2?
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What is the command to move a file named file1 to another file named file2?
What is the command to move a file named file1 to another file named file2?
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How do you remove a file named file1 using the command line?
How do you remove a file named file1 using the command line?
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Which states can a process be in according to the process state diagram?
Which states can a process be in according to the process state diagram?
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Context switching is the process of saving the context of the current process and loading the state of a new process.
Context switching is the process of saving the context of the current process and loading the state of a new process.
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What is a zombie process?
What is a zombie process?
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What does the execlp() system call do?
What does the execlp() system call do?
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The fork() system call creates a new process by copying the current process.
The fork() system call creates a new process by copying the current process.
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What are the advantages of cooperating processes? Information sharing: Since several users may be interested in the same piece of information, we must provide an environment to allow concurrent users to access these types of resources. Computation speedup: If we want a particular task to run faster, we must break it into ____________.
What are the advantages of cooperating processes? Information sharing: Since several users may be interested in the same piece of information, we must provide an environment to allow concurrent users to access these types of resources. Computation speedup: If we want a particular task to run faster, we must break it into ____________.
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Match the following communication characteristics with their descriptions:
Match the following communication characteristics with their descriptions:
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Study Notes
Introduction to Operating Systems
- An operating system is a program that acts as an intermediary between a user and the computer hardware.
- It manages hardware and software resources, provides services to users, and controls the execution of programs.
Organization of a Computer System
- A computer system consists of:
- Hardware: provides basic computing resources (CPU, memory, I/O devices)
- Operating system: manages the use of hardware among application programs and provides a simple interface for users
- Application programs: define the ways in which system resources are used to solve computing problems
- Users: people, machines, or other computers
Purpose of a Computer System
- The primary purpose of a computer system is to execute programs efficiently and allow users to solve problems.
- The operating system provides services to achieve this purpose, including:
- Managing secondary storage devices
- Managing primary storage (memory)
- Managing processes
- Providing file management
- Providing security and integrity of data
Types of Operating Systems
- Single-user systems: allow only one user to use the computer at a time, maximizing user convenience and responsiveness.
- Batch systems: execute jobs in batches, where a job consists of a program, data, and control information.
- Multi-programmed systems: keep multiple jobs in memory simultaneously, increasing CPU utilization and throughput.
- Time-sharing systems: allow multiple users to use the computer simultaneously, with each user interacting with their processes.
- Real-time systems: have rigid time requirements, used in dedicated applications such as scientific experiments, medical imaging, and industrial control.
Interrupts, Traps, and Software Interrupts
- Interrupts: signals generated by hardware devices to get the CPU's attention.
- Traps (or exceptions): software-generated interrupts caused by errors or user requests for operating system services.
- Signals: events generated to get the attention of a process, such as SIGINT (Interrupt signal).### Hardware Protection
- To ensure proper operation, we must protect the operating system and other programs from malfunctioning programs.
- Issues of hardware protection include I/O protection, memory protection, and CPU protection.
Dual-Mode Operation
- To differentiate between a user process and the operating system code, we need two separate modes of operation: user mode and monitor mode (also called supervisor mode, system mode, or privileged mode).
- A bit, called the mode bit, is added to the hardware of the computer to indicate the current mode.
I/O Protection
- To prevent users from performing illegal I/O, all I/O instructions are defined as privileged instructions.
- Users cannot issue I/O instructions directly; they must do it through the operating system.
- I/O protection is complete if a user program can never gain control of the computer in monitor mode.
Memory Protection
- Memory protection is ensured by using two CPU registers: base register and limit register.
- Base register holds the smallest legal physical memory address for a process.
- Limit register contains the size of the process.
- The CPU checks that every address generated by the process falls within the memory range defined by the values stored in the base and limit registers.
CPU Protection
- To maintain control, we must ensure that the operating system maintains control.
- A timer is used to prevent a program from running too long.
- The timer period may be variable or fixed.
Operating System Components
- Process management:
- Creating and terminating processes
- Suspending and resuming processes
- Providing mechanisms for process synchronization and communication
- Main memory management:
- Keeping track of free memory space
- Keeping track of which parts of memory are currently being used and by whom
- Deciding which processes are to be loaded into memory when memory space becomes available
- Secondary storage management:
- Free-space management
- Storage allocation and deallocation
- Disk scheduling
- I/O system management:
- A memory management component
- A general device-driver interface
- Drivers for specific hardware devices
- File management:
- Creating and deleting files
- Creating and deleting directories
- Supporting primitives for manipulating files and directories
- Protection system:
- Controlling access of programs, processes, or users to the resources defined by a computer system
- Networking:
- Message routing and connection strategies
- Contention and security
- Command-line interpreter (shells):
- Reading user commands and executing them
- Providing an interface between the user and the operating system
Operating System Services
- Program execution:
- Loading a program into memory
- Running the program
- Ending the program's execution
- I/O operations:
- Reading and writing files
- I/O device management
- File system manipulation:
- Creating and deleting files
- Creating and deleting directories
- Communications:
- Exchanging information between processes
- Communication via shared memory or message passing
- Error detection:
- Detecting errors in the CPU and memory hardware
- Detecting errors in I/O devices and user programs
- Resource allocation:
- Scheduling jobs
- Allocating plotters, modems, and other peripheral devices
- Accounting:
- Keeping track of which users use how many and which kinds of computer resources
- Protection:
- Controlling access to system resources
- Ensuring that all access to system resources is controlled### Operating System Structures
- Simple/Monolithic Structure: no structure, written for functionality and efficiency; examples are DOS and UNIX.
- In UNIX, the kernel is separated into interfaces and device drivers, providing OS functions through system calls.
- The kernel is difficult to enhance due to its enormous functionality.
Layered Approach
- Breaks the OS into layers or levels, each built on top of the lower layer.
- The bottom layer is the hardware, and the highest layer is the user interface.
- Each layer consists of data structures and routines that can be invoked by higher-level layers.
- Advantages: modularity, simplified debugging, and system verification.
- Disadvantages: careful definition of layers, added overhead, and longer system calls.
Micro Kernels
- Structures the OS by removing non-essential components from the kernel and implementing them as system and user-level programs.
- Provides a smaller kernel with minimum process and memory management, and a communication facility.
- Advantages: ease of extending the OS, fewer modifications, easier porting, more security, and reliability.
- Examples: Mach, MacOS X Server, QNX, OS/2, and Windows NT.
Virtual Machines
- Conceptually, a computer system is made up of layers, with the kernel using hardware instructions to create system calls.
- System programs use either system calls or hardware instructions, and application programs view everything under them as part of the machine.
- Virtual machine (VM) approach: creates an illusion of a process having its own memory and virtual machine.
- Advantages: provides a robust level of security and allows system development without disrupting normal system operation.
- Examples: IBM VM operating system, Java Virtual Machine (JVM), and VMWare.
System Design and Implementation
- Design goals: user goals (easy to use, reliable, safe, and fast) and system goals (easy to design, implement, and maintain).
- Separation of mechanisms and policies: mechanisms determine how to do something, and policies determine what will be done.
- Implementation: traditionally written in assembly language, now in higher-level languages like C/C++ for faster development, compactness, and ease of understanding.
UNIX/Linux Directory Structure
- Hierarchical file system structure with a root directory (/) and other directories and files beneath it.
- Directories and files are represented by paths and filenames.
- Pathname: a list of directories separated by slashes (/).
- The last component of a path may be a file or directory.
- Types of pathnames: absolute (starts with the root directory), relative (starts with the home directory, current directory, or parent directory).
Directory Structure
- Important directories in the Linux directory hierarchy:
- /: The root directory.
- /bin: Essential binary executable files.
- /boot: System boot files.
- /dev: Devices available to Linux.
- /etc: System configuration files.
- /home: Personal directories for users.
- /lib: Shared libraries and kernel modules.
- /lost+found: Files restored after a crash or improper shutdown.
- /mnt: Temporary file systems.
- /opt: Large application packages.
- /proc: Virtual directory for system processes.
- /root: Home directory for the superuser.
- /sbin: System administration utilities.
- /tmp: Temporary files.
- /usr: Shareable, read-only directory for user applications.
- /var: Variable data files.
Browsing UNIX/Linux Directory Structure
- Commands for browsing the directory structure:
- ls: Displays the contents of a directory.
- ls -a: Displays all files in a directory, including hidden files.
- ls -l: Displays the long listing for the contents of a directory.
- Understanding the UNIX/Linux directory structure is essential for working with the system.
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Description
This quiz covers the concepts and topics related to operating systems, covering the basics, process management, memory management, and more. It is designed for CS604 students at Virtual University of Pakistan.
