atof(temp.c_str())

This is a C++ code snippet that converts a C++ string object "temp" to a double data type using the "atof()" function.

The "atof()" function is a standard C++ library function that converts a string containing a numerical value to a double data type. The "c_str()" function is used to convert the string object "temp" to a C-style string (i.e. a null-terminated character array) that is required as an argument to the "atof()" function.

Overall, this code allows the program to convert a string value to a floating-point value, which can be useful for various mathematical and computational operations.