diff --git a/src/completion.rs b/src/completion.rs
index 7747025139e01e59e9bd963fa361761769a69585..778bc43ad29422dce3e0cf30cb6f41069c952a33 100644
--- a/src/completion.rs
+++ b/src/completion.rs
@@ -68,6 +68,7 @@ pub struct FilenameCompleter {
     break_chars: BTreeSet<char>,
 }
 
+// rl_basic_word_break_characters, rl_completer_word_break_characters
 #[cfg(unix)]
 static DEFAULT_BREAK_CHARS: [char; 18] = [
     ' ', '\t', '\n', '"', '\\', '\'', '`', '@', '$', '>', '<', '=', ';', '|', '&', '{', '(', '\0',
diff --git a/src/config.rs b/src/config.rs
index 4c54e7999a7fed1db8f33464e2d0654a23587f7a..d1dbc42b6408049a2ec7b0e596fadf673e840564 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -5,7 +5,7 @@ use std::default::Default;
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct Config {
     /// Maximum number of entries in History.
-    max_history_size: usize,
+    max_history_size: usize, // history_max_entries
     history_duplicates: HistoryDuplicates,
     history_ignore_space: bool,
     completion_type: CompletionType,
diff --git a/src/edit.rs b/src/edit.rs
index e9004208ccfbbbbc259b3567fadf456282e72a9c..cea72afbea1bd6f16b63796fd66041aa4da3573f 100644
--- a/src/edit.rs
+++ b/src/edit.rs
@@ -19,7 +19,7 @@ use undo::Changeset;
 /// Implement rendering.
 pub struct State<'out, 'prompt> {
     pub out: &'out mut Renderer,
-    prompt: &'prompt str,  // Prompt to display
+    prompt: &'prompt str,  // Prompt to display (rl_prompt)
     prompt_size: Position, // Prompt Unicode/visible width and height
     pub line: LineBuffer,  // Edited line buffer
     cursor: Position,      /* Cursor position (relative to the start of the prompt
diff --git a/src/line_buffer.rs b/src/line_buffer.rs
index 2316a028dcf2d0f76f0e7cf88983af36cf673804..628d66a96b7f63ca73d9434e9ea2b511bf072961 100644
--- a/src/line_buffer.rs
+++ b/src/line_buffer.rs
@@ -47,8 +47,8 @@ pub trait ChangeListener: DeleteListener {
 ///
 /// The methods do text manipulations or/and cursor movements.
 pub struct LineBuffer {
-    buf: String, // Edited line buffer
-    pos: usize,  // Current cursor position (byte position)
+    buf: String, // Edited line buffer (rl_line_buffer)
+    pos: usize,  // Current cursor position (byte position) (rl_point)
     dl: Option<Rc<RefCell<DeleteListener>>>,
     cl: Option<Rc<RefCell<ChangeListener>>>,
 }
diff --git a/src/tty/mod.rs b/src/tty/mod.rs
index 72dc1fc1a65e35b1ffaf0485fad954ee91a43e67..1476be64ebb3e1abb8987d4c3f274f7f7a9a0c8e 100644
--- a/src/tty/mod.rs
+++ b/src/tty/mod.rs
@@ -116,8 +116,8 @@ impl<'a, R: Renderer + ?Sized> Renderer for &'a mut R {
 
 /// Terminal contract
 pub trait Term {
-    type Reader: RawReader;
-    type Writer: Renderer;
+    type Reader: RawReader; // rl_instream
+    type Writer: Renderer; // rl_outstream
     type Mode: RawMode;
 
     fn new() -> Self;