Stream I/O Routines

Routine	Attributes	Description
getchar	reentrant	Reads and echoes a character using the _getkey and putchar routines.
_getkey		Reads a character using the 8051 serial interface.
gets		Reads and echoes a character string using the getchar routine.
printf		Writes formatted data using the putchar routine.
printf517		Writes formatted data using the putchar routine.
putchar		Writes a character using the 8051 serial interface.
puts	reentrant	Writes a character string and newline ('\n') character using the putchar routine.
scanf		Reads formatted data using the getchar routine.
scanf517		Reads formatted data using the getchar routine.
sprintf		Writes formatted data to a string.
sprintf517		Writes formatted data to a string.
sscanf		Reads formatted data from a string.
sscanf517		Reads formatted data from a string.
ungetchar		Places a character back into the getchar input buffer.
vprintf		Writes formatted data using the putchar function.
vsprintf		Writes formatted data to a string.

The stream I/O routines are implemented as functions and are prototyped in the stdio.h include file.

The stream input and output routines allow you to read and write data to and from a user-defined I/O interface. Characters are read using the _getkey routine and are written using the putchar routine. The default _getkey and putchar functions in the C51 library read and write characters using the 8051 serial interface.

The source code for _getkey and putchar is available in the \KEIL\C51\LIB folder. You may modify these files and substitute them for the default library routines. The stream functions then perform input and output using your modified _getkey and putchar routines.

To use the existing _getkey and putchar routines, you must first initialize the 8051 serial port. If the serial port is not properly initialized, the default stream functions do not function. Initializing the serial port requires manipulating several special function registers (SFRs) of the 8051.