Operating Systems: Windows Shortcuts and Unix/Linux Commands

The 'du' (disk usage) command summarizes disk usage by directory, showing kilobytes used by each subdirectory. Option A incorrectly denies du exists. Option C misidentifies it as a user command (that's 'who' or 'users'). Option D describes 'df' (disk free), not du. Option B correctly describes du's purpose - reporting disk consumption by subdirectory.

The cat command outputs the entire file content at once, which can quickly scroll off the screen for large files. In contrast, the more command acts as a pager, displaying content one screenful at a time, making it much easier to read.

Running cat file1 > file1 empties the file because the shell truncates file1 for writing before cat can read it. The >> operator in the second command appends the specified files to report. Other options fail to recognize this truncation behavior.

The grep command searches input files for lines matching a specified pattern and prints those entire lines. It does not just output the matched pattern itself, nor is its primary definition restricted to conditional or multi-pattern searches, making the other options incorrect.

The 'kill' command terminates processes by PID (Process ID). Options A and B use non-existent commands (end, delete). Option D 'kill all' is not a valid command - kill requires specific PID(s). Option C 'kill pid' is correct: you use 'kill' followed by the process ID number to terminate that specific process.

A pipe (|) connects commands so the standard output of the left command becomes standard input for the right command. Option A correctly describes this mechanism. Option B is vague. Option C incorrectly limits pipes to awk only. Option D is incomplete. Pipes enable command chaining for complex data transformations.

The cat file2 command reads and displays the contents of file2 to the terminal. In contrast, cat > file2 redirects standard input to overwrite or create file2. The other options incorrectly claim they perform identical operations or cause errors.

The 'chmod' (change mode) command modifies file permissions in Unix. Option A 'Changemode' is fictional. Option C 'chper' doesn't exist. Option D incorrectly claims both exist. Option B correctly identifies 'chmod' as the command for permission management (read/write/execute for user/group/others).

Alt + Enter is the standard keyboard shortcut in Windows Explorer to open the Properties dialog for the selected folder or file. This shows detailed information including attributes, size, creation date, and more.

Alt + Spacebar is a Windows keyboard shortcut that opens the window control menu (system menu) for the active window. This menu contains options like Restore, Move, Size, Minimize, Maximize, and Close.

Holding the Shift key during Windows boot (specifically after the BIOS screen but before Windows logo) will trigger Safe Mode or the Advanced Boot Options menu. Safe Mode loads Windows with minimal drivers and services for troubleshooting.

Alt + Print Screen captures only the active window (the window currently in focus) to the clipboard, not the entire screen. The regular Print Screen key captures the entire desktop. Shift + Print Screen has no standard function in Windows.

Ctrl + Esc is the keyboard shortcut that opens the Windows Start menu. This is equivalent to clicking the Start button or pressing the Windows key. Alt + Esc cycles through windows in reverse order, and Ctrl + Tab switches between applications within some interfaces.

Pressing the Ctrl key along with the numeric keypad's + key in Windows Explorer's Details view automatically resizes all columns to fit their longest content. Other combinations like Ctrl + F2 or Alt + + do not perform this action, making them incorrect distractors.

The 'touch' command in Unix/Linux performs two functions: 1) If the file doesn't exist, it creates an empty file (0 bytes). 2) If the file already exists, it updates the file's timestamp to the current time. Therefore, option D 'b and c' is correct because touch does both of these things depending on whether the file exists.

Win+Tab opens Task View in Windows 10/11, showing all open windows in a visual interface. You can cycle through them with arrow keys or Tab, but pressing Enter is required to switch to the selected window, unlike Alt+Tab which switches immediately on each press. Option A is incorrect because Alt+Tab switches directly without a confirm step.

Win+Break (or Win+Pause) opens System Properties in all Windows versions, displaying basic computer information like Windows edition, processor, RAM, and computer name. Options A, B, and D are incorrect: Win+P opens display projection (second screen), Win+F10 has no default system action, and Win+S opens search (Windows 10/11).

Pressing Win + D first minimizes all open windows, showing the desktop; pressing it again restores the windows to their previous state. Thus both “Minimises all windows” and “Unminimises all windows” describe its behavior, while the other options do not.