write-char character &optional output-stream → character

character — a character.

output-stream – an output stream designator. The default is standard output.

write-char outputs character to output-stream.

 (write-char #\a) 
⊳ a 
→ #\a 
 (with-output-to-string (s) 
   (write-char #\a s) 
   (write-char #\Space s) 
   (write-char #\b s)) 
→ "a b"

The output-stream is modified.

*standard-output*, *terminal-io*.

read-char, write-byte, write-sequence