what is the need for retarget option in IS keil3

retarget printf in embedded

hi..
i am working in arm9 board..
IDE IS keil3 version..
in all sample program..they given the retarget option..
what is the need of that..
reply me

retarget fputc

Hello there.

Always a retarget option is given so that there are few Ic's in ARM9 fmaily that do not support some feature or some may have a little more feature than the present controller. e.g once ARM 9 is released to the market, after sometime some new feature might be added into the same ARM9 due to lot of demand. but the keil might not have updated it in the software which we use., so they came up with concept of retarget which uses the old features but in case your program is written for some new feature it is taken from retarget and the compilation is done or else the program might not compile and give error that the device do not supprot the feature.

Is it clear,

Re: about retarget option..

here is explaination with summary
The higher-level input/output, such as the functions fscanf() and fprintf(), and the C++ object std::cout, are not target-dependent. However, the higher-level functions perform input/output by calling lower-level functions that are target-dependent. To retarget input/output, you can either avoid these higher-level functions or redefine the lower-level functions.
You can provide your own implementation of C Library functions that make use of target hardware, and that are automatically linked in to your image in favor of the C library implementations. For example, you might have a peripheral I/O device such as a UART, and you might want to override the library implementation of fputc(), that writes to the debugger console, with one that outputs to the UART. Because this implementation of fputc() is linked in to the final image, the entire printf() family of functions prints out to the
UART.