In the FIFO (First-In-First-Out) page replacement algorithm, the oldest page is chosen for replacement. This means that the page that has been in memory the longest (i.e., the one that was loaded first) will be replaced when a page fault occurs and a new page needs to be brought into memory. Therefore, the correct option is 1. oldest page is chosen.

From the given options, the correct choice for a unique tag that identifies the file within the file system is 1. File identifier. The file identifier, commonly known as the inode number, serves as a unique identifier for a file within a file system. It is assigned to each file's corresponding inode and is used by the operating system to locate and manage the file's data. The file name and file type, on the other hand, are attributes associated with the file but do not necessarily provide a unique identification within the file system.

To create a file in a file system, both options (a) and (b) are correct:

1. Allocate the space in the file system: When creating a file, the file system needs to allocate space on the storage media to store the file's data. This involves reserving a portion of the disk or other storage device to hold the contents of the file.

2. Make an entry for the new file in the directory: The file system also needs to keep track of the file's existence and location. This is done by making an entry in the directory, which is a data structure that organizes and maintains a list of file names along with their corresponding metadata, such as the file's inode number and location.

Therefore, the correct answer is option 3. both (a) and (b).

The correct answer is option 4. all of the mentioned.

By using system calls, you can perform all of the mentioned operations:

1. Open the file: The `open()` system call is used to open a file, creating a file descriptor that allows subsequent operations on the file.

2. Read the file: The `read()` system call is used to read data from a file. It takes the file descriptor, buffer, and the number of bytes to read as parameters.

3. Write into the file: The `write()` system call is used to write data into a file. It takes the file descriptor, buffer containing the data to be written, and the number of bytes to write as parameters.

Therefore, all of the mentioned options can be accomplished using specific system calls.

File types can be represented by file extensions. A file extension is a suffix added to the end of a filename, separated by a period (.) character. It is typically composed of a few characters that indicate the file's format or type. For example:

- .txt represents a text file.
- .jpg or .jpeg represents an image file in JPEG format.
- .mp3 represents an audio file in the MP3 format.
- .docx represents a Microsoft Word document file.

File extensions help both the operating system and users identify the type of content contained within a file and determine which application or program should be used to open or process it.

The mapping of files is managed by the file system. The file system is responsible for organizing and managing files on storage devices such as hard drives or solid-state drives. It provides a structure and set of operations for creating, storing, retrieving, and managing files and directories.

The file system manages the mapping of files by maintaining data structures, such as directories, inodes (index nodes), allocation tables, or other metadata that store information about the location, size, and attributes of

File system fragmentation occurs when unused space or single files are not contiguous.

Option A. "Unused space or single file are not contiguous" accurately describes file system fragmentation. It refers to situations where free space or individual files are scattered in non-contiguous blocks on the storage media.

Fragmentation can occur in two forms:

1. External Fragmentation: This type of fragmentation happens when free space is broken up into small non-contiguous chunks, making it challenging to allocate contiguous blocks for new files.

2. Internal Fragmentation: Internal fragmentation occurs when the allocated blocks for a file are larger than the actual file size, resulting in wasted space within the allocated blocks.

Both forms of fragmentation can lead to decreased performance and inefficiencies in file storage and retrieval.

Therefore, the correct option is A. "Unused space or single file are not contiguous."

If one or more devices use a common set of wires to communicate with the computer system, the connection is called a "bus."

A bus is a communication pathway or channel that allows data and control signals to transfer between various components and devices within a computer system. It serves as a shared connection or medium through which multiple devices can exchange information with the central processing unit (CPU) or other components.

The bus can be internal, connecting components within the computer system, or external, connecting devices outside the computer system. Examples of buses include the system bus, such as the front-side bus (FSB) connecting the CPU to the main memory, or peripheral buses like USB (Universal Serial Bus) connecting external devices to the computer.

Therefore, the correct term for this type of connection is a "bus."

A "controller" is a collection of electronics that can operate a port, a bus, or a device.

A controller is a hardware component or integrated circuit that manages the communication and operation of a specific port, bus, or device within a computer system. It is responsible for controlling the flow of data, managing protocols, handling data transfers, and coordinating the interaction between the connected devices.

Controllers exist for various purposes and interfaces, such as disk controllers for managing data transfer between the computer's storage devices (e.g., hard drives or solid-state drives) and the rest of the system, USB controllers for managing USB ports and devices, network controllers for handling network communications, and so on.

In summary, a controller is a collection of electronics that provides the necessary functionality and control to operate a port, a bus, or a device within a computer system.

The correct option for the missing terms in the given statement would be D. input, output.

An I/O port typically consists of four registers: status, control, data, and input/output (I/O) registers.

1. Status Register: This register provides information about the current status or condition of the I/O port.
2. Control Register: This register is used to configure or control the behavior of the I/O port.
3. Data Register: This register is responsible for the actual transfer of data between the I/O port and the processor.
4. Input/Output (I/O) Register: This register facilitates the input and output operations for the connected device.

Therefore, the missing terms in the statement are "input" and "output."