just a copy-paste fix I suppose....

Author: karelv

Language/Functions/Characters/isPrintable.adoc

@@ -25,7 +25,7 @@ Analyse if a char is printable (that is any character that produces an output, e
 === Syntax
 [source,arduino]
 ----
-`isAlpha(thisChar)`
+`isPrintable(thisChar)`
 ----
 
 [float]