int fputc (byte,fileid)
int byte;
int fileid; 

where:

This macro writes the contents of the next byte to a file. You must define the identity of the file with either the fopen macro or the FOPEN command.

The file written to must be opened in write mode, for example:

fopen(100,"c:\\myfiles\\data_out.txt","w").

Example shows you how to use fputc in a macro.