// just like the standard printf except it recognises only the
// following format directives: %i, %u, %x, %s

extern int printf(char *str, ...);

// standard puts

extern int puts(char *s);

// replacement of the standard putchar

extern int putc(char c);

// prints an unsigned int with:
//  - f == 'x' => as an hex string
//  - f == 'u' => as a decimal string

extern int putu(int u, char f);

// prints a signed int as decimal string

extern int puti(int i);