I/O support code
Most applications use calls to the standard C library. However, when you initially link libc.a, several I/O functions are undefined. If you dont plan on doing any input or output, youve no concerns; otherwise, you need to create two functions, open() and close(). These dont need to be fully supported unless you have a file system, so they are normally stubbed out, using kill().
sbrk()is also a stub, since you cant do process control on an embedded system, since process control is only needed by applications that do dynamic memory allocation. It uses the variable, _end, which is set in the linker script.
The following routines are also used for optimization.
- -inbyte
- Returns a single byte from
the console.
- Used for low-level debugging,
takes an argument for print()
and prints a byte out to the console (typically used for ASCII text).
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