diff --git a/src/include/pv.h b/src/include/pv.h
index 05ccfa6..4d3a4d1 100644
--- a/src/include/pv.h
+++ b/src/include/pv.h
@@ -1,5 +1,5 @@
 /*
- * Functions used across the program.  Include "config.h" first.
+ * Functions used across the program.
  *
  * Copyright 2002-2008, 2010, 2012-2015, 2017, 2021, 2023 Andrew Wood
  *
diff --git a/src/main/main.c b/src/main/main.c
index d556f76..ada0b20 100644
--- a/src/main/main.c
+++ b/src/main/main.c
@@ -11,6 +11,7 @@
 #include "options.h"
 #include "pv.h"
 
+/* We do not set this because it breaks "dd" - see below. */
 /* #undef MAKE_STDOUT_NONBLOCKING */
 
 #include <stdio.h>
diff --git a/src/pv/file.c b/src/pv/file.c
index deeb117..8cd9dbd 100644
--- a/src/pv/file.c
+++ b/src/pv/file.c
@@ -1,5 +1,5 @@
 /*
- * Functions for opening and closing files.
+ * Functions for opening and closing files, and calculating their size.
  *
  * Copyright 2002-2008, 2010, 2012-2015, 2017, 2021, 2023 Andrew Wood
  *
diff --git a/src/pv/loop.c b/src/pv/loop.c
index 1db72a2..9255f94 100644
--- a/src/pv/loop.c
+++ b/src/pv/loop.c
@@ -1,6 +1,5 @@
 /*
- * Main program entry point - read the command line options, then perform
- * the appropriate actions.
+ * Functions providing the main transfer or file descriptor watching loop.
  *
  * Copyright 2002-2008, 2010, 2012-2015, 2017, 2021, 2023 Andrew Wood
  *
diff --git a/src/pv/string.c b/src/pv/string.c
index 1c97693..9e58f08 100644
--- a/src/pv/string.c
+++ b/src/pv/string.c
@@ -1,5 +1,5 @@
 /*
- * Functions for converting strings to numbers.
+ * Functions for portably managing strings.
  *
  * Copyright 2023 Andrew Wood
  *
diff --git a/src/pv/transfer.c b/src/pv/transfer.c
index 8daf22a..c289e8d 100644
--- a/src/pv/transfer.c
+++ b/src/pv/transfer.c
@@ -1,5 +1,5 @@
 /*
- * Functions for transferring between file descriptors.
+ * Functions for transferring data between file descriptors.
  *
  * Copyright 2002-2008, 2010, 2012-2015, 2017, 2021, 2023 Andrew Wood
  *