diff --git a/c/qrcodegen.c b/c/qrcodegen.c
index de13309..1fd70ba 100644
--- a/c/qrcodegen.c
+++ b/c/qrcodegen.c
@@ -86,7 +86,8 @@ static int numCharCountBits(enum qrcodegen_Mode mode, int version);
 
 /*---- Private tables of constants ----*/
 
-// For checking text and encoding segments.
+// The set of all legal characters in alphanumeric mode, where each character
+// value maps to the index in the string. For checking text and encoding segments.
 static const char *ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
 
 // For generating error correction codes.
diff --git a/c/qrcodegen.h b/c/qrcodegen.h
index 3215a6c..8ac9d3f 100644
--- a/c/qrcodegen.h
+++ b/c/qrcodegen.h
@@ -172,12 +172,15 @@ bool qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcod
 
 /* 
  * Tests whether the given string can be encoded as a segment in alphanumeric mode.
+ * A string is encodable iff each character is in the following set: 0 to 9, A to Z
+ * (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
  */
 bool qrcodegen_isAlphanumeric(const char *text);
 
 
 /* 
  * Tests whether the given string can be encoded as a segment in numeric mode.
+ * A string is encodable iff each character is in the range 0 to 9.
  */
 bool qrcodegen_isNumeric(const char *text);
 
diff --git a/cpp/QrSegment.hpp b/cpp/QrSegment.hpp
index 565778f..8e1356f 100644
--- a/cpp/QrSegment.hpp
+++ b/cpp/QrSegment.hpp
@@ -126,12 +126,15 @@ class QrSegment final {
 	
 	/* 
 	 * Tests whether the given string can be encoded as a segment in alphanumeric mode.
+	 * A string is encodable iff each character is in the following set: 0 to 9, A to Z
+	 * (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
 	 */
 	public: static bool isAlphanumeric(const char *text);
 	
 	
 	/* 
 	 * Tests whether the given string can be encoded as a segment in numeric mode.
+	 * A string is encodable iff each character is in the range 0 to 9.
 	 */
 	public: static bool isNumeric(const char *text);
 	
@@ -198,7 +201,8 @@ class QrSegment final {
 	
 	/*---- Private constant ----*/
 	
-	/* The set of all legal characters in alphanumeric mode, where each character value maps to the index in the string. */
+	/* The set of all legal characters in alphanumeric mode, where
+	 * each character value maps to the index in the string. */
 	private: static const char *ALPHANUMERIC_CHARSET;
 	
 };
diff --git a/java/io/nayuki/qrcodegen/QrSegment.java b/java/io/nayuki/qrcodegen/QrSegment.java
index 74dbc1b..da04109 100644
--- a/java/io/nayuki/qrcodegen/QrSegment.java
+++ b/java/io/nayuki/qrcodegen/QrSegment.java
@@ -222,13 +222,19 @@ public final class QrSegment {
 	
 	/*---- Constants ----*/
 	
-	/** Can test whether a string is encodable in numeric mode (such as by using {@link #makeNumeric(String)}). */
+	/** Describes precisely all strings that are encodable in numeric mode. To test whether a
+	 * string {@code s} is encodable: {@code boolean ok = NUMERIC_REGEX.matcher(s).matches();}.
+	 * A string is encodable iff each character is in the range 0 to 9. */
 	public static final Pattern NUMERIC_REGEX = Pattern.compile("[0-9]*");
 	
-	/** Can test whether a string is encodable in alphanumeric mode (such as by using {@link #makeAlphanumeric(String)}). */
+	/** Describes precisely all strings that are encodable in alphanumeric mode. To test whether a
+	 * string {@code s} is encodable: {@code boolean ok = ALPHANUMERIC_REGEX.matcher(s).matches();}.
+	 * A string is encodable iff each character is in the following set: 0 to 9, A to Z
+	 * (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon. */
 	public static final Pattern ALPHANUMERIC_REGEX = Pattern.compile("[A-Z0-9 $%*+./:-]*");
 	
-	/** The set of all legal characters in alphanumeric mode, where each character value maps to the index in the string. */
+	/** The set of all legal characters in alphanumeric mode, where
+	 * each character value maps to the index in the string. */
 	static final String ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
 	
 	
diff --git a/javascript/qrcodegen.js b/javascript/qrcodegen.js
index 7579698..e275cbd 100644
--- a/javascript/qrcodegen.js
+++ b/javascript/qrcodegen.js
@@ -834,13 +834,19 @@ var qrcodegen = new function() {
 	
 	var QrSegment = {};  // Private object to assign properties to. Not the same object as 'this.QrSegment'.
 	
-	// (Public) Can test whether a string is encodable in numeric mode (such as by using QrSegment.makeNumeric()).
+	// (Public) Describes precisely all strings that are encodable in numeric mode.
+	// To test whether a string s is encodable: var ok = NUMERIC_REGEX.test(s);
+	// A string is encodable iff each character is in the range 0 to 9.
 	this.QrSegment.NUMERIC_REGEX = /^[0-9]*$/;
 	
-	// (Public) Can test whether a string is encodable in alphanumeric mode (such as by using QrSegment.makeAlphanumeric()).
+	// (Public) Describes precisely all strings that are encodable in alphanumeric mode.
+	// To test whether a string s is encodable: var ok = ALPHANUMERIC_REGEX.test(s);
+	// A string is encodable iff each character is in the following set: 0 to 9, A to Z
+	// (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
 	this.QrSegment.ALPHANUMERIC_REGEX = /^[A-Z0-9 $%*+.\/:-]*$/;
 	
-	// (Private) The set of all legal characters in alphanumeric mode, where each character value maps to the index in the string.
+	// (Private) The set of all legal characters in alphanumeric mode,
+	// where each character value maps to the index in the string.
 	QrSegment.ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
 	
 	
diff --git a/python/qrcodegen.py b/python/qrcodegen.py
index 4a6c14c..55319cf 100644
--- a/python/qrcodegen.py
+++ b/python/qrcodegen.py
@@ -733,10 +733,16 @@ class QrSegment(object):
 	
 	# ---- Constants ----
 	
-	# (Public) Can test whether a string is encodable in numeric mode (such as by using make_numeric())
+	# (Public) Describes precisely all strings that are encodable in numeric mode.
+	# To test whether a string s is encodable: ok = NUMERIC_REGEX.fullmatch(s) is not None
+	# A string is encodable iff each character is in the range 0 to 9.
 	NUMERIC_REGEX = re.compile(r"[0-9]*\Z")
 	
-	# (Public) Can test whether a string is encodable in alphanumeric mode (such as by using make_alphanumeric())
+	# (Public) Describes precisely all strings that are encodable in alphanumeric mode.
+	# To test whether a string s is encodable: ok = ALPHANUMERIC_REGEX.fullmatch(s) is not None
+	# A string is encodable iff each character is in the following set: 0 to 9, A to Z
+	# (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
+
 	ALPHANUMERIC_REGEX = re.compile(r"[A-Z0-9 $%*+./:-]*\Z")
 	
 	# (Private) Dictionary of "0"->0, "A"->10, "$"->37, etc.
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index 8e3ea1e..de2fca8 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -1002,12 +1002,15 @@ impl QrSegment {
 	
 	
 	// Tests whether the given string can be encoded as a segment in alphanumeric mode.
+	// A string is encodable iff each character is in the following set: 0 to 9, A to Z
+	// (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
 	fn is_alphanumeric(text: &[char]) -> bool {
 		text.iter().all(|c| ALPHANUMERIC_CHARSET.contains(c))
 	}
 	
 	
 	// Tests whether the given string can be encoded as a segment in numeric mode.
+	// A string is encodable iff each character is in the range 0 to 9.
 	fn is_numeric(text: &[char]) -> bool {
 		text.iter().all(|c| '0' <= *c && *c <= '9')
 	}
diff --git a/typescript/qrcodegen.ts b/typescript/qrcodegen.ts
index aa31b85..49e0d7c 100644
--- a/typescript/qrcodegen.ts
+++ b/typescript/qrcodegen.ts
@@ -799,13 +799,19 @@ namespace qrcodegen {
 		
 		/*-- Constants --*/
 		
-		// Can test whether a string is encodable in numeric mode (such as by using QrSegment.makeNumeric()).
+		// Describes precisely all strings that are encodable in numeric mode. To test
+		// whether a string s is encodable: let ok: boolean = NUMERIC_REGEX.test(s);
+		// A string is encodable iff each character is in the range 0 to 9.
 		public static readonly NUMERIC_REGEX: RegExp = /^[0-9]*$/;
 		
-		// Can test whether a string is encodable in alphanumeric mode (such as by using QrSegment.makeAlphanumeric()).
+		// Describes precisely all strings that are encodable in alphanumeric mode. To test
+		// whether a string s is encodable: let ok: boolean = ALPHANUMERIC_REGEX.test(s);
+		// A string is encodable iff each character is in the following set: 0 to 9, A to Z
+		// (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
 		public static readonly ALPHANUMERIC_REGEX: RegExp = /^[A-Z0-9 $%*+.\/:-]*$/;
 		
-		// The set of all legal characters in alphanumeric mode, where each character value maps to the index in the string.
+		// The set of all legal characters in alphanumeric mode,
+		// where each character value maps to the index in the string.
 		private static readonly ALPHANUMERIC_CHARSET: string = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
 		
 	}