[此贴子已经被作者于2007-8-31 14:01:50编辑过]

"而Hello LED生成的代码只有几百个字节，当然是没有用到printf函数
这个Hello World工程代码到底多在了哪儿？"

你可以看看nios_led的说明：

 * This example is a freestanding program because it's entry point is the
 * function:
 *
 *    void alt_main (void)
 *
 * As opposed to "main()" as a "hosted" application would (see the
 * "hello_world" example).
 *
 * Upon entry to alt_main():
 * - The CPU's caches (if any) have been initialized.
 * - The stack-pointer has been set.
 * - That's all. The rest is up to you.
 *
 * If you modify this example and try to call C library functions such as
 * printf, they will NOT  work unless you explicitly initialize the system.
 * If you wish to use C library calls, it is strongly suggested you start
 * with the hosted hello_world template which uses main() as it's entry
 * point.
 *
 * On the other hand, if you want to write a program that gets-in even
 * earlier, you will need to provide your own assembly-language machine-setup
 * code by defining the symbol "_start". Any definition of _start in your
 * directory will override the library definition. You can find source code
 * for the Nios II library _start here:

主要是alt_main.c和alt_sys_init.c引入的代码
而这俩文件又间接引入了很多设备驱动代码，比如系统包含定时器，则定时器的驱动会被自动加载到最终的可执行文件...

更详细的资料自己研究吧或者等我的书出版^_^