you can't because you can't stuff a whole string into a single character. If this is about some error message you got, then post the error message along with the code you wrote.

A string cannot be cast to a char, because a char is one byte and a string can be any number of bytes. You can, however, use std::string's c_str member and create a const char* out of your string.
This can be useful if you want to copy the value into a character array, which might look like this: Or, if you want to return a single character from a string you can either use the [] operator or the at member.

Do you mean string to char* ? You could access the c_str() , which is of type const char*.

ok , can I typecast string into double?

I want to convert string 12.12 to double 12.12

You can do this using stringstreams, as long as you validate the string first to make sure that it is in-fact a double value, otherwise your program will crash. An explicit cast of string to double is not supported, however.

OMG NO !!! You should NEVER typecast a string to a numeric type. Use something like strtod() to convert a char* to a double, or use stringstream, see here