cIn

Cin is most commonly encountered as the standard input stream in the C++ programming language, written as cin in code. In C++, cin is part of the iostream library and is typically referred to as std::cin. It provides access to the program’s standard input device, usually the keyboard, and is used with the extraction operator (>>) to read formatted values into variables.

Usage is straightforward: cin reads input according to the type of the destination variable. For example, int x; std::cin >> x; reads an integer from input. The operator>> skips leading whitespace and stops at a character that does not match the target type, leaving any remaining input (such as a trailing newline) in the buffer. To read an entire line of text, programs often use std::getline in combination with cin and handle leftover newlines. By default, cin is an instance of std::istream and is tied to std::cout, meaning input operations may flush the output buffer before reading; this tie can be disabled for performance.

Performance and portability notes: To improve I/O performance, programmers may disable synchronization with C I/O by calling ios::sync_with_stdio(false) and untie cin from cout with cin.tie(nullptr). These changes affect interaction with C-style I/O and should be used consistently within a program. Beyond programming, the string “Cin” or its capitalized form can appear as a proper noun in unrelated contexts, such as personal names or place names, but those uses are not related to the C++ feature.