Ctrl+Alt+Del

• ​Control–Alt–Delete (often abbreviated to Ctrl+Alt+Del, also known as the “three-finger salute”)

 is a computer keyboard command on IBM PC compatible computers, invoked by pressing the Delete key while holding the Control and Alt keys: Ctrl+Alt+Delete. The function of the key combination differs depending on the context but it generally interrupts or facilitates interrupting a function. For instance, in pre-boot environment (before an operating system starts) or in DOS, Windows 3.0 and earlier versions of Windows or OS/2, the key combination reboots the computer. Starting with Windows 3.1, the command invokes a task manager or security related component that facilitates ending a Windows session.

• On some Linux-based operating systems including Ubuntu and Debian, Control+Alt+Delete is a shortcut for logging out.

On Ubuntu Server, it is used to reboot a computer without logging in.

• Ctrl+Alt+Delete is not a keyboard shortcut on macOS platforms. Instead, ⌘ Command+⌥ Option+Esc can be used to bring up the Force Quit Menu. However, in the macOS Server logon screen, pressing Control+⌥ Option+Delete (as the Option key is the equivalent of Alt key on a Mac keyboard) will show an alert saying “This is not DOS.”Control+⌘ Command+Power immediately restarts the computer.

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standard-c-library-reference

Standard library header files in C++

Hello everyone we have seen Hello world program in C++

The first line of the program Hello World we can see its written #include.What is actually, well writing C/C++ program we need to write this.This is header file in C++.

In the C++ programming language, the C++ Standard Library is a collection of classes and functions, which are written in the core language and part of the C++ ISO Standard itself. The C++ Standard Library provides several generic containers, functions to utilize and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for everyday tasks such as finding the square root of a number. The C++ Standard Library also incorporates 18 headers of the ISO C90 C standard library ending with “.h”, but their use is deprecated. No other headers in the C++ Standard Library end in “.h”. Features of the C++ Standard Library are declared within the std namespace.

The C++ Standard Library is based upon conventions introduced by the Standard Template Library (STL), and has been influenced by research in generic programming and developers of the STL such as Alexander Stepanov and Meng Lee. Although the C++ Standard Library and the STL share many features, neither is a strict superset of the other.

A noteworthy feature of the C++ Standard Library is that it not only specifies the syntax and semantics of generic algorithms, but also places requirements on their performance.These performance requirements often correspond to a well-known algorithm, which is expected but not required to be used. In most cases this requires linear time O(n) or linearithmic time O(n log n), but in some cases higher bounds are allowed, such as quasilinear time O(n log² n) for stable sort (to allow in-place merge sort). Previously sorting was only required to take O(n log n) on average, allowing the use of quicksort, which is fast in practice but has poor worst-case performance, but introsort was introduced to allow both fast average performance and optimal worst-case complexity, and as of C++11, sorting is guaranteed to be at worst linearithmic. In other cases requirements remain laxer, such as selection, which is only required to be linear on average (as in quickselect), not requiring worst-case linear as in introselect.

The C++ Standard Library underwent ISO standardization as part of the C++ ISO Standardization effort, and is undergoing further work regarding standardization of expanded functionality.

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