File Concepts and Student Marks
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Questions and Answers

What is a directory structure primarily used for?

  • To increase the speed of file creation
  • To organize many files in the file system (correct)
  • To encrypt files for security
  • To improve file duplication

Which operation allows you to remove a file from the directory?

  • Search for a file
  • Delete a file (correct)
  • Rename a file
  • List a directory

What is a drawback of a single-level directory structure?

  • It is too complex for users
  • It requires too much storage space
  • It allows easy file retrieval
  • File name conflicts can occur (correct)

In a two-level directory system, what is the role of the root directory?

<p>It acts as the first-level directory (B)</p> Signup and view all the answers

How does a tree-structured directory solve the issues present in two-level directories?

<p>By creating subdirectories to manage large numbers of files (A)</p> Signup and view all the answers

Which operation allows you to change the name of a file within a directory?

<p>Rename a file (A)</p> Signup and view all the answers

What is a major advantage of a two-level directory system compared to a single-level directory?

<p>Elimination of file name conflicts among users (D)</p> Signup and view all the answers

Which of the following best describes the purpose of traversing the file system?

<p>To access every directory and file within the structure (B)</p> Signup and view all the answers

What happens to the read pointer after a read operation is completed?

<p>It is updated to the next read location. (A)</p> Signup and view all the answers

Which operation is referred to as 'file seek'?

<p>Repositioning the current file position pointer. (D)</p> Signup and view all the answers

When truncating a file, what remains after the operation?

<p>The file attributes. (C)</p> Signup and view all the answers

What file extension is commonly associated with executable files?

<p>.exe (D)</p> Signup and view all the answers

What does the operating system require to load an executable file?

<p>A defined internal file structure. (C)</p> Signup and view all the answers

In UNIX OS, how are all files defined?

<p>As streams of bytes. (C)</p> Signup and view all the answers

What is the logical record size of files in UNIX?

<p>1 byte. (B)</p> Signup and view all the answers

What is one consequence of an OS supporting multiple file structures?

<p>It increases the size of the OS. (B)</p> Signup and view all the answers

What does a free block contain in a linked free space list?

<p>Pointer to the next free block (A)</p> Signup and view all the answers

What is the main advantage of the grouping approach in linked free space lists?

<p>It allows easy access to multiple free blocks at once. (C)</p> Signup and view all the answers

What is a significant drawback of the linear list implementation in directory management?

<p>Searching for unique file names can be time-consuming. (D)</p> Signup and view all the answers

How does the hash table enhance the directory management process compared to a linear list?

<p>By allowing random access to directory entries. (C)</p> Signup and view all the answers

In the counting approach of free space management, what information is stored in the entries?

<p>Address of the first free block and the count of following free blocks (B)</p> Signup and view all the answers

What must happen when a new file is created in a linear list directory implementation?

<p>The entire list is checked for unique file names. (A)</p> Signup and view all the answers

What role does the hash function play in directory management using hash tables?

<p>To generate keys for efficient searching. (B)</p> Signup and view all the answers

What happens during the process of file deletion in a linear list directory?

<p>The whole list needs to be traversed. (C)</p> Signup and view all the answers

What characterizes synchronous I/O operations?

<p>CPU execution halts while I/O operations are performed. (A)</p> Signup and view all the answers

Which I/O communication method allows for data transfer without CPU intervention after setup?

<p>Direct Memory Access (DMA) (D)</p> Signup and view all the answers

In memory-mapped I/O, which of the following is true?

<p>Memory addresses are used both by memory and I/O devices. (B)</p> Signup and view all the answers

What is the main benefit of using Direct Memory Access (DMA) with fast devices?

<p>It minimizes the CPU's time spent handling interrupts. (C)</p> Signup and view all the answers

Which of the following best describes Special Instruction I/O?

<p>It utilizes specific CPU instructions tailored for I/O control. (B)</p> Signup and view all the answers

What information does the file control block (FCB) contain?

<p>File ownership, permissions, and location of file contents (D)</p> Signup and view all the answers

What is typically a limitation of memory-mapped I/O?

<p>It relies heavily on CPU involvement for data transfer. (B)</p> Signup and view all the answers

Which statement accurately reflects how DMA operates?

<p>DMA requires CPU intervention only during the transfer. (C)</p> Signup and view all the answers

What does the Boot Control Block do?

<p>Contains information needed to boot an OS from a specific volume (C)</p> Signup and view all the answers

When a file is opened, what does the open() call do first?

<p>Searches the system-wide open file table for the file (C)</p> Signup and view all the answers

Which of the following is NOT an approach to communicate with the CPU and I/O devices?

<p>Control Port I/O (B)</p> Signup and view all the answers

What happens when a process closes a file?

<p>The per-process table entry is removed and the open count is decremented (C)</p> Signup and view all the answers

Which of the following accurately describes the Volume Control Block?

<p>It provides details about the number of blocks and free block count for a volume (C)</p> Signup and view all the answers

What information is copied into the system-wide open file table during the open process?

<p>An existing FCB and tracking details for the open file (D)</p> Signup and view all the answers

What is an essential function of the directory structure in a file system?

<p>To provide a mechanism for organizing files within the system (D)</p> Signup and view all the answers

What occurs after all processes that opened a file close it?

<p>Metadata is updated and FCB entry is removed from the system-wide open file table (B)</p> Signup and view all the answers

What is the primary role of the DMA controller during a data transfer process?

<p>To transfer bytes to the buffer continuously until a counter reaches zero (D)</p> Signup and view all the answers

Which layer of I/O software provides a direct interface for user programs?

<p>User Level Libraries (A)</p> Signup and view all the answers

What characterizes device-independent I/O software?

<p>It enables programs to interact with multiple devices without modification (B)</p> Signup and view all the answers

What is a primary responsibility of device drivers within an operating system?

<p>To encapsulate device-specific code and provide a standard interface (B)</p> Signup and view all the answers

When a DMA transfer is complete, what action does the DMA controller take?

<p>It interrupts the CPU to signal the completion (D)</p> Signup and view all the answers

Which statement about device drivers is accurate?

<p>They handle communication between device-independent software and device controllers (C)</p> Signup and view all the answers

What happens to counter C during a DMA transfer?

<p>It decreases with each byte transferred until it reaches zero (B)</p> Signup and view all the answers

Which of the following is NOT a task performed by device drivers?

<p>Initiate CPU scheduling for concurrent processes (D)</p> Signup and view all the answers

Flashcards

Directory Structure

A collection of files grouped together in a hierarchical structure to organize and manage them.

Single-Level Directory

A single directory that acts as the root or starting point for all files.

Two-Level Directory

A directory system with two levels: a root directory and user-specific directories.

Tree-Structured Directory

A hierarchical directory structure where each directory can have subdirectories, creating branches like a tree.

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Search for a file

Finding a specific file within a directory structure.

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Create a file

Adding a new file to a directory.

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Delete a file

Removing a file from a directory.

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List a directory

Displaying the list of files and subdirectories within a directory.

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Read Pointer

The position within a file where the next read or write operation will occur.

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File Seek

The process of moving the read pointer to a specific location within a file.

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Truncating a File

The process of removing the contents of a file while keeping the file metadata (name, permissions, etc.) intact.

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Logical Record

A portion of a file that is considered a single unit of data.

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Physical Disk Block

The physical storage unit on a disk, which can hold a certain number of bytes.

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File Structure

The way in which data is organized and stored within a file.

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Executable File

A file containing machine instructions that can be executed directly by the computer.

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Source Code File

A file that contains the source code of a program written in a programming language.

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Linked Free Space List on Disk

A method for managing free disk blocks where each free block contains a pointer to the next free block. The starting block's address is stored separately on disk and in memory.

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Grouping (Linked Free Space List)

A variation of the linked free space list where the first free block stores pointers to the n-1 following free blocks, along with a pointer to the next block containing free block pointers.

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Counting Free Space

A simple approach where free space is managed by keeping track of the first free block and the number of subsequent free blocks.

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Linear List Directory

A directory implementation where files are stored as a singly linked list. Each file contains pointers to its data blocks and the next file in the directory.

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Linear List: Search Inefficiency

A disadvantage of the linear list directory where searching for a file requires traversing the entire list, which can be inefficient for large directories.

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Hash Table Directory

An alternative to linear lists that utilizes a hash table to store key-value pairs for each file. The key is generated by a hash function applied to the file name, and the value points to the file's location.

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Hash Table: Efficient Search

In a hash table directory, searching for files is efficient because the hash function allows direct access to the relevant file entry, eliminating the need to traverse the entire list.

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Hash Table: Key-Value Pair

The key-value pairs used in a hash table directory are generated by applying a hash function to the file name, which maps to the corresponding file's location in the directory.

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File Control Block (FCB)

A data structure within a file system that contains information about a file. It stores details like file size, ownership, permissions, and location of file contents.

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System-Wide Open File Table

A table in memory that stores information about open files (FCBs) and tracks the number of processes accessing each file. It enables efficient file sharing and access control.

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Per-Process Open File Table

A table specific to each process, maintaining a pointer to the system-wide open file table entry for a file and additional file-specific details like current position and access mode.

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Opening a File

The process of preparing a file for reading or writing operations. Involves searching the file system to locate the file, creating a system-wide open file table entry, and establishing a per-process open file table entry.

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Closing a File

The action of releasing a previously open file, removing its entry from the per-process open file table and decrementing the count in the system-wide open file table. If no processes have the file open, any updated metadata is written back to the disk.

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Volume Control Block (VCB)

A special block on a disk that stores information about the volume, including size, block size, free space counters, and pointers to free blocks.

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Boot Control Block

A data structure that stores details about a volume, including the information needed to boot an operating system from it. If the volume doesn't contain an operating system, it can be empty.

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Synchronous I/O

The CPU waits for I/O operations to complete before resuming execution.

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Asynchronous I/O

I/O operations happen concurrently with CPU execution, allowing the CPU to continue working while data is transferred.

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Special Instruction I/O

This method uses specialized CPU instructions to send and receive data between the CPU and I/O devices.

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Memory-mapped I/O

I/O devices share the same address space as memory, allowing direct data transfers without CPU involvement.

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Direct Memory Access (DMA)

This method involves transferring data directly between memory and the I/O device without the need for CPU intervention.

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DMA Controller (DMAC)

This hardware component manages the transfer of data between the I/O device and memory during Direct Memory Access (DMA).

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Interrupt

The way a device informs the CPU that it has completed an operation.

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Buffer

A temporary storage area in memory used during data transfers between an I/O device and the CPU.

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Device Driver

A device driver is a software module that interacts directly with the device hardware. It translates requests from the operating system (OS) into commands that the specific hardware understands.

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DMA (Direct Memory Access)

DMA (Direct Memory Access) is a hardware mechanism that allows devices to communicate with the main memory directly, without involving the CPU. This offloads the CPU from handling data transfers, improving efficiency.

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DMA Controller

The DMA controller manages data transfer between devices and memory. It handles the transfer process and ensures efficient data flow, making the process faster and more efficient.

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Kernel Level Modules

The kernel-level modules are responsible for interacting with specific hardware devices. These modules function as bridges between the device drivers and the operating system, ensuring smooth and efficient communication.

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Device-Independent I/O Modules

Device-independent I/O modules ensure that applications can interact with various devices using a standardized interface. This removes the need to write specific code for each device, increasing code reusability and flexibility.

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User-Level Libraries

The user-level libraries provide a simple interface for applications to perform I/O operations. They abstract the complexities of device communication, simplifying the code for user programs.

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DMA Interrupt

When the DMA transfer is complete, the DMA controller interrupts the CPU, alerting it that the data has been successfully moved. This signals to the CPU that it can proceed with the next operation.

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Study Notes

File Concept

  • Computers store information on various media (magnetic disks, tapes, optical disks).
  • The operating system converts physical storage into logical storage units called files.
  • A file is a collection of similar records.
  • A record is a collection of related fields.
  • A field holds a single data value.
  • A database is a collection of related data.

Student Marks

  • Example data: KUMA (marks 85, 86, Pass), LAKSH (marks 93, 92, Pass)
  • Each row of data represents a record (e.g., LAKSH, 93, 92, P).
  • A collection of such records is a data file.

File Attributes

  • Name: A descriptive name for the file (e.g., report.txt).
  • Identifier: A unique tag used to identify files in the file system.
  • Type: Based on file extension (.exe, .obj, .src for executable, object, and source files respectively).
  • Location: Pointer to a device and the file location on it.
  • Size: File size in bytes, words or blocks.
  • Protection: Access control information (read, write, execute).
  • Time, Date, User ID: Created, last modified and last accessed information, and user details.

File Operations

  • Creating: Two steps - verify space availability and make an entry for the new file in the directory.
  • Writing: Requires file name and data to be written. The system locates the file and uses a write pointer to position data.
  • Reading: Locates the file in the directory and uses a read pointer to read data, updating it after each read.
  • Repositioning: Moving the file position pointer to a specific value (file seek).
  • Deleting: Locating the file, releasing file space and erasing the directory entry.
  • Truncating: Removing the file's contents without changing attributes.

File Types and Extensions

  • File types are determined by their extensions (e.g., .exe, .txt, .pdf).
  • Extensions determine the purpose of the file.

File Structure

  • Files are structured as a series of blocks.
  • File sizes and structure are determined by operating system.

File Access Methods

  • Sequential Access: Processing records sequentially (one after the other), often used with magnetic tapes.
  • Direct (or Relative) Access: Random access to any record without any specific order (used for disk-based files).
  • Indexed Sequential Access: Files are organized in a sequence based on a key field, making accessing faster (often used in combination with indexes).

Directory Structure

  • Method of organizing files in the file system, grouping files to make them easier to manage.
  • Single-level directory: One directory for all files.
  • Two-level directory: Separate directories for each user, avoiding file naming collisions.
  • Tree-structured directory: Directories organized in a hierarchical tree structure (subdirectories and sub-subdirectories).
  • Acyclic graph directory: Shared directories used in collaborative projects.

File System Structure

  • Disk is the primary storage for files.
  • Key characteristics enable efficient storage: rewriting in place and direct access to blocks.

Internal File Structure

  • UNIX defines files as byte streams with each byte addressable by offset.
  • Blocks: Physical file blocks contain multiple logical records or bytes
  • Internal fragmentation: wasted space in a block due to difference between physical and logical file sizes
  • File access and storage methods are defined by the OS.

I/O Control

  • The I/O subsystem acts as an interface for device drivers to communicate with memory and disk devices.
  • Device drivers implement specific interactions with I/O devices, enabling data transfer to/from storage.

Synchronous/Asynchronous I/O

  • Synchronous I/O stops CPU execution while waiting for I/O operations.
  • Asynchronous I/O performs I/O operations concurrently with CPU execution.

Communication with I/O Devices

  • CPU communicates with I/O devices through various methods.
  • I/O special instructions, memory mapped I/O and DMA are part of the methods to communicate.

Device Controllers

  • Interfaces between devices and the I/O subsystem.
  • Handle complex communication with I/O devices efficiently.

Allocation Methods

  • Contiguous: Stores files in a continuous set of blocks, potentially leading to fragmentation (external).
  • Linked: Files stored as a linked list of blocks.
  • Indexed: Files with an index block holding pointers to data blocks.

Free Space Management

  • File system manages free space efficiently using various techniques.
  • Linked free lists and bitmaps are methods.

Directory Implementation

  • Linear List: File directory implemented as a singly linked list.
  • Hash table: More efficient implementation of directories.

Efficiency and Performance

  • Disk allocation and directory algorithms impact performance.
  • Disk cache and read/write techniques improve performance.

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Chapter 7 PDF - File Concepts

Description

This quiz explores the concepts of files in computer systems, focusing on how data is organized and represented. You'll learn about file attributes, data records, and how information is stored in files. Brush up on your knowledge of file systems and database records with this engaging quiz.

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