13.4.2. istream Member Functions peek, putback and ignore

The ignore member function of istream reads and discards a designated number of characters (the default is one) or terminates upon encountering a designated delimiter (the default is EOF, which causes ignore to skip to the end of the file when reading from a file).

The putback member function places the previous character obtained by a get from an input stream back into that stream. This function is useful for applications that scan an input stream looking for a field beginning with a specific character. When that character is input, the application returns the character to the stream, so the character can be included in the input data.

The peek member function returns the next character from an input stream but does not remove the character from the stream.