replace ASCII by macro call
diff --git a/Doc/ref/ref3.tex b/Doc/ref/ref3.tex
index 0904849..152b1bf 100644
--- a/Doc/ref/ref3.tex
+++ b/Doc/ref/ref3.tex
@@ -211,7 +211,7 @@
Characters represent (at least) 8-bit bytes. The built-in
functions \verb@chr()@ and \verb@ord()@ convert between characters
and nonnegative integers representing the byte values.
-Bytes with the values 0-127 represent the corresponding ASCII values.
+Bytes with the values 0-127 represent the corresponding \ASCII{} values.
The string data type is also used to represent arrays of bytes, e.g.
to hold data read from a file.
\obindex{string}
@@ -221,10 +221,10 @@
\bifuncindex{chr}
\bifuncindex{ord}
-(On systems whose native character set is not ASCII, strings may use
+(On systems whose native character set is not \ASCII{}, strings may use
EBCDIC in their internal representation, provided the functions
-\verb@chr()@ and \verb@ord()@ implement a mapping between ASCII and
-EBCDIC, and string comparison preserves the ASCII order.
+\verb@chr()@ and \verb@ord()@ implement a mapping between \ASCII{} and
+EBCDIC, and string comparison preserves the \ASCII{} order.
Or perhaps someone can propose a better rule?)
\index{ASCII}
\index{EBCDIC}