diff --git a/builtin/stl.knox b/builtin/stl.knox
index e93992d..69a692f 100644
--- a/builtin/stl.knox
+++ b/builtin/stl.knox
@@ -1,12 +1,24 @@
-// TODO: stl should be a module, not a class.
+// TODO: stl should be a module, not a class?
 class stl {
+    // Standard input and output.
     func print(x : string) void {}
+
+    // File input and output.
+
+    // List operations.
     func range(start : int, end : int, step : int) [int] { return [0]; }
 
+    // Bitwise.
     func and(x : int, y : int) int { return 0; }
     func or(x : int, y : int) int { return 0; }
     func not(x : int) int { return 0; }
     func xor(x : int, y : int) int { return 0; }
     func left(x : int, y : int) int { return 0; }
     func right(x : int, y : int) int { return 0; }
+
+    // Math.
+    func random(min : int, max : int) int { return 0; }
+    func randomf(min : float, max : float) float { return 0; }
+    // func randomd(min : double, max : double) double { return 0; }
+    // func seed
 }
\ No newline at end of file
diff --git a/emitter/emitter.go b/emitter/emitter.go
index 7424012..5ea3a5d 100644
--- a/emitter/emitter.go
+++ b/emitter/emitter.go
@@ -26,12 +26,10 @@ func Generate(node *ast.Node) string {
 func header() string {
 	code := ""
 	code += "#include <stdlib.h>\n#include <stdio.h>\n#include <string.h>\n#include <stdint.h>\n#include <stdbool.h>\n#include <stddef.h>\n#include \"knoxutil.h\"\n\n" // TODO: #130 Only include what is needed.
+	// TODO: Main should set seed.
 	return code
 }
 
-// TODO: Declare all functions first, before definitions, to avoid ordering issues.
-// TODO: Main needs to return int.
-
 func program(node *ast.Node) string {
 	head := header()
 
@@ -234,6 +232,8 @@ func funcCall(node *ast.Node) string {
 			funcName = "printf"
 			argList = expr(&node.Children[1])
 			return funcName + "(\"%s\", " + argList + ");"
+
+		// Bitwise.
 		case "and":
 			return "(" + expr(&node.Children[1]) + " & " + expr(&node.Children[2]) + ")"
 		case "or":
@@ -246,6 +246,12 @@ func funcCall(node *ast.Node) string {
 			return "(" + expr(&node.Children[1]) + " >> " + expr(&node.Children[2]) + ")"
 		case "xor":
 			return "(" + expr(&node.Children[1]) + " ^ " + expr(&node.Children[2]) + ")"
+
+		// Math.
+		case "random":
+			return "random(" + expr(&node.Children[1]) + ", " + expr(&node.Children[2]) + ")"
+		case "randomf":
+			return "randomf(" + expr(&node.Children[1]) + ", " + expr(&node.Children[2]) + ")"
 		}
 
 	}
diff --git a/emitter/knoxutil.h b/emitter/knoxutil.h
index 6080194..88ed4a8 100644
--- a/emitter/knoxutil.h
+++ b/emitter/knoxutil.h
@@ -4,6 +4,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+// Concatensate two strings.
 char* concat(const char *s1, const char *s2)
 {
     const size_t len1 = strlen(s1);
@@ -15,6 +16,7 @@ char* concat(const char *s1, const char *s2)
     return result;
 }
 
+// Copy the contents of one string to a new string.
 char* copy(const char *s)
 {
     const size_t len = strlen(s);
@@ -22,4 +24,16 @@ char* copy(const char *s)
     // TODO: Check for malloc errors.
     memcpy(result, s, len + 1);
     return result;
+}
+
+int random(int min, int max) {
+    return (rand() % (max - min + 1)) + min; 
+}
+
+float randomf(float min, float max) {
+    return min + ((float)rand() / RAND_MAX) * (max - min);
+}
+
+double randomd(double min, double max) {
+    return min + ((double)rand() / RAND_MAX) * (max - min);
 }
\ No newline at end of file