Difference between freestanding and hosted implementations

Hi, everyone.

It occurs to me that when I am programming on, say OSX with gcc, the operating system designers and gcc writers between them have given me certain means of input and output. For example, I can use printf() to print a message to the screen.

But when I am programming an AVR microcontroller, printf() doesn't have much meaning. There is no screen, and no way that the AVR can "print", unless I implement it myself.

Is this what is meant by the difference between a "hosted" implementation and a "freestanding" one? As in, a hosted implementation gives me certain standard ways of communicating with the environment, and a freestanding one is presumably going to have to rely on something architecture-specific?

Richard

An hosted implementation has access to all of the C Standard library; a free-standing implementation does not necessarily have access to any function defined in the Standard library.

Specifically, a C99 freestanding implementation, only has to provide the macros and types declared in the standard headers <float.h>, <iso646.h>, <limits.h>, <stdarg.h>, <stdbool.h>, <stddef.h>, and <stdint.h> and need not provide support for complex numbers.

printf is used for output streams such as USART.

Just search avrfreaks for usart.h and set up a stream - You'll be able to get lots of info there on how to do that

I used a header by Joerg Wunsch which has been slightly modified to suit the ATmega128 CONTROLLER