The OS is responsible for allocating space on the hard disk.

The operating system manages the allocation of space on the hard disk.

Files are broken up into blocks.

Files are divided into blocks, which are equal to or less than the sector size of the hard drive.

Sector size is set when the file system is created.

The sector size of a storage device is determined when the file system is created, with NTFS using sectors from 512 bytes to 64 kibibytes.

Each block of a file is placed into an empty sector.

File blocks are placed into empty sectors, and they may not be placed into contiguous sectors.

Wasted (slack) space is left if the whole sector is not filled.

If a sector is not completely filled, it results in wasted or slack space.

Calculate the number of blocks needed to store a 2.8 KiB file.

Number of blocks = ⌈(2.8 × 1024) ÷ 512⌉ = 6 blocks

Why is the ceiling function used in block calculation?

Only whole blocks can be used, so the ceiling function is applied.

The OS maintains information on which users are able to do what actions to each file.

Access permissions control who can do what with each file.

Definition of processes in computing

Programs in the memory that are being executed (or waiting to be) are called processes.

Role of the CPU when a program is run

When a program is run, it is copied from the secondary storage into the memory so that it can be executed by the CPU.

Visibility of processes to the user

Some processes are visible to the user, but there are many that run in the background.

Simultaneous access to the CPU

Often there are many processes that need to access the CPU simultaneously.

CPU's capability in executing instructions

Each CPU can only carry out one instruction at a time.

Operating System's responsibility regarding CPU time

The OS is responsible for allocating CPU time to each of the processes, alongside access to other hardware such as the memory and peripherals.

Multitasking in modern CPUs and operating systems

Modern CPUs and operating systems can make multiple processes available at the same time, known as multitasking.

Role of the operating system in multitasking

The OS ensures all processes can execute by allocating them a fair share of time with the hardware.

Difference between single-core and multi-core CPUs

A CPU with one core allows one instruction in one process at a time, while a CPU with multiple cores allows one instruction in one process at a time on each core.

First In First Out (FIFO) scheduling

Processes the queue in the order that items arrive. The process at the front of the queue runs first.

Shortest Job First scheduling

The process closest to being completed goes first.

Round-robin scheduling

Processes are allocated a time slice in the CPU. If not complete, they return to the queue. Higher priority tasks get more time slices.

Advantages of Round-robin

- Balanced throughput (number of processes completed over time). - Average response time is good if the number of processes is low. - Processes can never be 'starved' of access to hardware as every process gets a turn; there is no priority system.

Disadvantages of Round-robin

- Some overhead (wasted time) is involved in switching between processes. - Processes may have to wait a long time to complete, especially if there are many waiting.

Advantages of Shortest Job First

- Average wait time is low. - Response time for short processes is very fast. - Lower overhead as there may be less task switching.

Disadvantages of Shortest Job First

- Longer processes may be starved of processing time if many shorter processes keep being executed. - Execution time must be known ahead of time; an average of previous execution times is often used.

- Low overhead: Task switching only happens when a process has completed, and the queue is never reorganized. - Processes are never starved of CPU time.

Disadvantages of FIFO

- Throughput may be low as longer processes may cause wait times to be high. - Response and completion times depend on the state of the queue. - There is no prioritization of tasks, so time-sensitive processes may not meet their deadlines.

The CPU is not the only hardware a process accesses.

Processes also need to use the computer's memory.

When a process is loaded into memory, the OS assigns it a series of addresses.

These blocks of addresses are called pages.

Management of pages is often done with a specific method.

A paging algorithm is used to manage pages.

Virtual memory is used when a computer's RAM becomes full.

The OS temporarily moves some contents of the RAM to a space on the hard drive.

The part of the hard drive used as an extension to the main memory is called virtual memory.

Virtual memory acts as an extension to the main memory.

Reopening a minimized program may take a few seconds due to virtual memory.

This delay occurs because the program's data is moved back from virtual memory to RAM.

Definition of the word "peripheral"

The word peripheral means 'on the edge' or 'secondary to something else'.

Function of peripheral devices

Peripheral devices are additional hardware that are connected to a computer.

Location of peripherals

Peripherals can be inside or outside the computer case itself.

Types of peripheral devices

There are many types of peripheral devices used in modern computing systems.

The user interface (UI) of an operating system is the point at which the human user and the system interact.

User interfaces facilitate interaction between users and systems.

The most common and familiar user interface is the graphical user interface (GUI).

GUIs use visual elements like windows, icons, and buttons.

The command line interface (CLI) is another common interface, particularly used in industry.

CLIs allow users to interact with the system through text commands.

Less common interfaces include menu-driven interfaces, such as those on ATMs.

Menu-driven interfaces guide users through options using menus.

Most GUIs use the WIMP format, which stands for Windows, Icons, Menus, and Pointer.

Command line interfaces (CLIs) are less familiar to most users.

CLIs are typically used by those needing to control computers, servers, or networks at a complex level.

CLIs lack icons or pointers.

Users interact by typing commands for execution.

PCS 4 Flashcards Flashcards

Student preview

57 questions

Show all answers

1.

FLASHCARD QUESTION

Front

Two types of software needed for computers to be useful

Back

System software and application software

2.

FLASHCARD QUESTION

Front

Definition of system software

Back

Programs that enable a computer to function, including the operating system and utility programs

3.

FLASHCARD QUESTION

Front

Definition of application software

Back

Programs that the user interacts with most, such as spreadsheets, web browsers, and games

4.

FLASHCARD QUESTION

Front

Operating system responsibilities

Back

The operating system performs many tasks, including process management, file management, user management, and peripheral management.

5.

FLASHCARD QUESTION

Front

Process management

Back

Organizing instructions in memory so that they can be processed.

6.

FLASHCARD QUESTION

Front

File management

Back

Organizing the contents of secondary storage.

7.

FLASHCARD QUESTION

Front

User management

Back

Providing a user interface and access levels.

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