"You are very unlikely to find a scanf as it reads the standard input stream on a 8052 is very hardware dependant"

That's an odd thing. Keil implement scanf(), if you don't want it to read from the UART you replace their _getkey() routine with one that reads from wherever you want it to. Does SDCC implement sscanf()?

"There is a printf because you usualy know what the data format is by the time you want to output it."

I don't really see the difference. printf() writes to the standard output stream which is equally hardware dependent. Also, I usually know the data format when I want to input it...