diff --git a/macros.tex b/macros.tex
index 10a9673..47905f3 100644
--- a/macros.tex
+++ b/macros.tex
@@ -343,7 +343,7 @@
 \newcommand{\Putc}{\dec{Putc}}
 \newcommand{\putc}{\dec{putc}}
 \newcommand{\UFile}{\dec{File}}
-\newcommand{\UFD}{\dec{FileDescr}}
+\newcommand{\UFD}{\dec{INumber}}
 \newcommand{\fwrite}{\dec{fwrite}}
 \newcommand{\iter}{\dec{iter}}
 \newcommand{\stdout}{\dec{stdout}}
diff --git a/thesis.tex b/thesis.tex
index 865f534..5fd1b3a 100644
--- a/thesis.tex
+++ b/thesis.tex
@@ -2057,11 +2057,11 @@ operation $\Write$ for writing a list of characters to the file.
   \BIO \defas \{\Write : \Record{\UFD;\String} \opto \UnitType\}
 \]
 %
-The operation is parameterised by a file descriptor ($\UFD$) and a
-character. We will leave the file descriptor type abstract until
+The operation is parameterised by an $\UFD$ and a character
+sequence. We will leave the $\UFD$ type abstract until
 Section~\ref{sec:tiny-unix-io}, however, we will assume the existence
 of a term $\stdout : \UFD$ such that we perform invocations of
-$\Putc$.
+$\Write$.
 %
 Let us define a suitable handler for this operation.
 %