scanf

A scanf format string (scan formatted) is a control parameter used in various functions to specify the layout of an input string. The functions can then divide the string and translate into values of appropriate data types. String scanning functions are often supplied in standard libraries. Scanf is a function that reads formatted data from the standard input string, which is usually the keyboard and writes the results whenever called in the specified arguments.

The term "scanf" comes from the C library, which popularized this type of function, but such functions predate C, and other names are used, such as readf in ALGOL 68. scanf format strings, which provide formatted input (parsing), are complementary to printf format strings, which provide formatted output (templating). These provide simple functionality and fixed format compared to more sophisticated and flexible parsers or template engines, but are sufficient for many purposes.