diff --git a/book/cha7.tex b/book/cha7.tex
index 735c356..bfe44ad 100644
--- a/book/cha7.tex
+++ b/book/cha7.tex
@@ -549,9 +549,8 @@ \section{Character classification}
 As an exercise, use the character classification and conversion
 library to write functions named {\tt stringToUpper} and
 {\tt stringToLower} that take a single {\tt string} as
-a parameter, and that modify the string by converting all the
-letters to upper or lower case.  The return type should be
-{\tt void}.
+a parameter, and return a string with all the characters converted to
+upper or lower case. The return type should be {\tt string}.
 
 \section{Other {\tt string} functions}