The linker automatically chooses an appropriate formatter for printf- and scanf-related function based on information from the compiler.
If that information is missing or insufficient, for example if printf is used through a function pointer, if the object file is old, etc,
then the automatic choice is the Full formatter.
In this case you might want to choose a formatter manually.
To override the default formatter for all the printf- and scanf-related functions, except for wprintf and wscanf variants,
you simply set the appropriate library options. This section describes the different options available.
When you set up your application project, you typically need to consider what printf and scanf formatting capabilities your application requires
If the provided formatters do not meet your requirements, you can customize the full formatters.
However, that means you must rebuild the runtime library.
The default behavior of the printf and scanf formatters are defined by configuration symbols in the file DLib_Defaults.h.
These configuration symbols determine what capabilities the function printf should have:
When you build a library, these configurations determine what capabilities the function scanf should have:
IAR EWARM PRINTF/SCANF FORMATTER
原文：http://www.cnblogs.com/shangdawei/p/3966239.html