diff --git a/build/scscript.js b/build/scscript.js
index 338feca..296e2bd 100644
--- a/build/scscript.js
+++ b/build/scscript.js
@@ -1,7 +1,7 @@
 (function(global) {
 "use strict";
 
-var sc = { VERSION: "0.0.21" };
+var sc = { VERSION: "0.0.22" };
 
 // src/sc/sc.js
 (function(sc) {
@@ -18,6 +18,16 @@ var sc = { VERSION: "0.0.21" };
     installer(sc);
   };
 
+  // istanbul ignore next
+  SCScript.stdout = function(msg) {
+    console.log(msg);
+  };
+
+  // istanbul ignore next
+  SCScript.stderr = function(msg) {
+    console.error(msg);
+  };
+
   SCScript.VERSION = sc.VERSION;
 
   global.SCScript = sc.SCScript = SCScript;
@@ -3975,6 +3985,29 @@ var sc = { VERSION: "0.0.21" };
 
 })(sc);
 
+// src/sc/lang/io.js
+(function(sc) {
+
+  var io = {};
+
+  var SCScript = sc.SCScript;
+  var buffer   = "";
+
+  io.post = function(msg) {
+    var items;
+
+    items  = (buffer + msg).split("\n");
+    buffer = items.pop();
+
+    items.forEach(function(msg) {
+      SCScript.stdout(msg);
+    });
+  };
+
+  sc.lang.io = io;
+
+})(sc);
+
 // src/sc/lang/dollarSC.js
 (function(sc) {
 
@@ -4233,6 +4266,7 @@ var sc = { VERSION: "0.0.21" };
     newClass._Spec = constructor;
     constructor.prototype.__class = newClass;
     constructor.prototype.__Spec  = constructor;
+    constructor.prototype.__className = className;
 
     metaClass._Spec = constructor;
     metaClass._isMetaClass = true;
@@ -5009,10 +5043,27 @@ var sc = { VERSION: "0.0.21" };
     };
 
     // TODO: implements dump
-    // TODO: implements post
-    // TODO: implements postln
-    // TODO: implements postc
-    // TODO: implements postcln
+
+    spec.post = function() {
+      this.asString().post();
+      return this;
+    };
+
+    spec.postln = function() {
+      this.asString().postln();
+      return this;
+    };
+
+    spec.postc = function() {
+      this.asString().postc();
+      return this;
+    };
+
+    spec.postcln = function() {
+      this.asString().postcln();
+      return this;
+    };
+
     // TODO: implements postcs
     // TODO: implements totalFree
     // TODO: implements largestFreeBlock
@@ -9932,6 +9983,17 @@ var sc = { VERSION: "0.0.21" };
     // TODO: implements writeInputSpec
     // TODO: implements case
     // TODO: implements makeEnvirValPairs
+
+    spec.asString = function() {
+      var items = [];
+      this.do($SC.Function(function($elem) {
+        items.push($elem.__str__());
+      }));
+
+      return $SC.String(
+        this.__className + "[ " + items.join(", ") + " ]"
+      );
+    };
   });
 
 })(sc);
@@ -12288,6 +12350,12 @@ var sc = { VERSION: "0.0.21" };
     spec.includes = function($item) {
       return $SC.Boolean(this._.indexOf($item) !== -1);
     };
+
+    spec.asString = function() {
+      return $SC.String("[ " + this._.map(function(elem) {
+        return elem.__str__();
+      }).join(", ") + " ]");
+    };
   });
 
   sc.lang.klass.refine("RawArray", function(spec, utils) {
@@ -12307,6 +12375,7 @@ var sc = { VERSION: "0.0.21" };
 (function(sc) {
 
   var fn  = sc.lang.fn;
+  var io  = sc.lang.io;
   var $SC = sc.lang.$SC;
 
   sc.lang.klass.refine("String", function(spec, utils) {
@@ -12476,10 +12545,26 @@ var sc = { VERSION: "0.0.21" };
       return $SC("String");
     };
 
-    // TODO: implements postln
-    // TODO: implements post
-    // TODO: implements postcln
-    // TODO: implements postc
+    spec.postln = function() {
+      io.post(this.__str__() + "\n");
+      return this;
+    };
+
+    spec.post = function() {
+      io.post(this.__str__());
+      return this;
+    };
+
+    spec.postcln = function() {
+      io.post("// " + this.__str__() + "\n");
+      return this;
+    };
+
+    spec.postc = function() {
+      io.post("// " + this.__str__());
+      return this;
+    };
+
     // TODO: implements postf
     // TODO: implements format
     // TODO: implements matchRegexp
diff --git a/package.json b/package.json
index 577f4ea..d621268 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "scscript",
-  "version": "0.0.21",
+  "version": "0.0.22",
   "author": "Nao Yonamine <mohayonao@gmail.com>",
   "homepage": "http://mohayonao.github.io/SCScript/",
   "bugs": "https://github.com/mohayonao/SCScript/issues",
diff --git a/src/sc/lang/classlib.js b/src/sc/lang/classlib.js
index 54e7630..9543218 100644
--- a/src/sc/lang/classlib.js
+++ b/src/sc/lang/classlib.js
@@ -5,6 +5,7 @@
   require("./klass");
   require("./iterator");
   require("./fn");
+  require("./io");
   require("../libs/random");
   require("../libs/mathlib");
 
diff --git a/src/sc/lang/classlib/Collections/ArrayedCollection.js b/src/sc/lang/classlib/Collections/ArrayedCollection.js
index 7dfd48b..4f22a56 100644
--- a/src/sc/lang/classlib/Collections/ArrayedCollection.js
+++ b/src/sc/lang/classlib/Collections/ArrayedCollection.js
@@ -754,6 +754,12 @@
     spec.includes = function($item) {
       return $SC.Boolean(this._.indexOf($item) !== -1);
     };
+
+    spec.asString = function() {
+      return $SC.String("[ " + this._.map(function(elem) {
+        return elem.__str__();
+      }).join(", ") + " ]");
+    };
   });
 
   sc.lang.klass.refine("RawArray", function(spec, utils) {
diff --git a/src/sc/lang/classlib/Collections/ArrayedCollection_test.js b/src/sc/lang/classlib/Collections/ArrayedCollection_test.js
index efad39c..ef82c8d 100644
--- a/src/sc/lang/classlib/Collections/ArrayedCollection_test.js
+++ b/src/sc/lang/classlib/Collections/ArrayedCollection_test.js
@@ -1225,6 +1225,14 @@
         },
       ]);
     });
+    it("#asString", function() {
+      var instance, test;
+
+      instance = this.createInstance([ 1, 2, 3 ]);
+
+      test = instance.asString();
+      expect(test).to.be.a("SCString").that.equals("[ 1, 2, 3 ]");
+    });
   });
 
   describe("SCRawArray", function() {
diff --git a/src/sc/lang/classlib/Collections/Collection.js b/src/sc/lang/classlib/Collections/Collection.js
index f29a200..b49a521 100644
--- a/src/sc/lang/classlib/Collections/Collection.js
+++ b/src/sc/lang/classlib/Collections/Collection.js
@@ -936,6 +936,17 @@
     // TODO: implements writeInputSpec
     // TODO: implements case
     // TODO: implements makeEnvirValPairs
+
+    spec.asString = function() {
+      var items = [];
+      this.do($SC.Function(function($elem) {
+        items.push($elem.__str__());
+      }));
+
+      return $SC.String(
+        this.__className + "[ " + items.join(", ") + " ]"
+      );
+    };
   });
 
 })(sc);
diff --git a/src/sc/lang/classlib/Collections/Collection_test.js b/src/sc/lang/classlib/Collections/Collection_test.js
index 5ce0cd9..019fd91 100644
--- a/src/sc/lang/classlib/Collections/Collection_test.js
+++ b/src/sc/lang/classlib/Collections/Collection_test.js
@@ -1208,5 +1208,13 @@
     });
     it.skip("#makeEnvirValPairs", function() {
     });
+    it("#asString", function() {
+      var instance, test;
+
+      instance = this.createInstance([ 1, 2, 3 ]);
+
+      test = instance.asString();
+      expect(test).to.be.a("SCString").that.equals("Array[ 1, 2, 3 ]");
+    });
   });
 })();
diff --git a/src/sc/lang/classlib/Collections/String.js b/src/sc/lang/classlib/Collections/String.js
index 6a02f46..bdd9146 100644
--- a/src/sc/lang/classlib/Collections/String.js
+++ b/src/sc/lang/classlib/Collections/String.js
@@ -4,6 +4,7 @@
   require("./ArrayedCollection");
 
   var fn  = sc.lang.fn;
+  var io  = sc.lang.io;
   var $SC = sc.lang.$SC;
 
   sc.lang.klass.refine("String", function(spec, utils) {
@@ -173,10 +174,26 @@
       return $SC("String");
     };
 
-    // TODO: implements postln
-    // TODO: implements post
-    // TODO: implements postcln
-    // TODO: implements postc
+    spec.postln = function() {
+      io.post(this.__str__() + "\n");
+      return this;
+    };
+
+    spec.post = function() {
+      io.post(this.__str__());
+      return this;
+    };
+
+    spec.postcln = function() {
+      io.post("// " + this.__str__() + "\n");
+      return this;
+    };
+
+    spec.postc = function() {
+      io.post("// " + this.__str__());
+      return this;
+    };
+
     // TODO: implements postf
     // TODO: implements format
     // TODO: implements matchRegexp
diff --git a/src/sc/lang/classlib/Collections/String_test.js b/src/sc/lang/classlib/Collections/String_test.js
index 4c8b534..b4a692a 100644
--- a/src/sc/lang/classlib/Collections/String_test.js
+++ b/src/sc/lang/classlib/Collections/String_test.js
@@ -232,14 +232,50 @@
       test = instance.species();
       expect(test).to.equal(SCString);
     });
-    it.skip("#postln", function() {
-    });
-    it.skip("#post", function() {
-    });
-    it.skip("#postcln", function() {
-    });
-    it.skip("#postc", function() {
-    });
+    it("#postln", sinon.test(function() {
+      var instance, test;
+
+      this.stub(sc.lang.io, "post");
+
+      instance = this.createInstance("post");
+
+      test = instance.postln();
+      expect(test).to.equal(instance);
+      expect(sc.lang.io.post).to.be.calledWith("post\n");
+    }));
+    it("#post", sinon.test(function() {
+      var instance, test;
+
+      this.stub(sc.lang.io, "post");
+
+      instance = this.createInstance("post");
+
+      test = instance.post();
+      expect(test).to.equal(instance);
+      expect(sc.lang.io.post).to.be.calledWith("post");
+    }));
+    it("#postcln", sinon.test(function() {
+      var instance, test;
+
+      this.stub(sc.lang.io, "post");
+
+      instance = this.createInstance("post");
+
+      test = instance.postcln();
+      expect(test).to.equal(instance);
+      expect(sc.lang.io.post).to.be.calledWith("// post\n");
+    }));
+    it("#postc", sinon.test(function() {
+      var instance, test;
+
+      this.stub(sc.lang.io, "post");
+
+      instance = this.createInstance("post");
+
+      test = instance.postc();
+      expect(test).to.equal(instance);
+      expect(sc.lang.io.post).to.be.calledWith("// post");
+    }));
     it.skip("#postf", function() {
     });
     it.skip("#format", function() {
diff --git a/src/sc/lang/classlib/Core/Kernel_test.js b/src/sc/lang/classlib/Core/Kernel_test.js
index c95860d..6cc56f9 100644
--- a/src/sc/lang/classlib/Core/Kernel_test.js
+++ b/src/sc/lang/classlib/Core/Kernel_test.js
@@ -3,8 +3,50 @@
 
   require("./Kernel");
 
-  describe("class Kernel", function() {
+  var $SC = sc.lang.$SC;
+
+  describe("SCKernel", function() {
     it.skip("write later", function() {
     });
   });
+
+  describe("SCInterpreter", function() {
+    var SCInterpreter, $interpreter;
+    before(function() {
+      SCInterpreter = $SC("Interpreter");
+      $interpreter = sc.lang.klass.$interpreter;
+    });
+    it(".new", function() {
+      expect(function() {
+        SCInterpreter.new();
+      }).to.throw("Interpreter.new is illegal.");
+    });
+    it("#<>a..z / #clearAll", function() {
+      var instance;
+
+      instance = $interpreter;
+
+      "abcdefghijklmnopqrstuvwxyz".split("").forEach(function(ch) {
+        var test, $value;
+
+        $value = sc.test.object();
+
+        test = instance[ch]();
+        expect(test).to.be.a("SCNil");
+
+        test = instance[ch + "_"]($value);
+        expect(test).to.equal(instance);
+
+        test = instance[ch]();
+        expect(test).to.equal($value);
+      });
+
+      instance.clearAll();
+
+      "abcdefghijklmnopqrstuvwxyz".split("").forEach(function(ch) {
+        var test = instance[ch]();
+        expect(test).to.be.a("SCNil");
+      });
+    });
+  });
 })();
diff --git a/src/sc/lang/classlib/Core/Object.js b/src/sc/lang/classlib/Core/Object.js
index 338ef50..2beaa60 100644
--- a/src/sc/lang/classlib/Core/Object.js
+++ b/src/sc/lang/classlib/Core/Object.js
@@ -43,10 +43,27 @@
     };
 
     // TODO: implements dump
-    // TODO: implements post
-    // TODO: implements postln
-    // TODO: implements postc
-    // TODO: implements postcln
+
+    spec.post = function() {
+      this.asString().post();
+      return this;
+    };
+
+    spec.postln = function() {
+      this.asString().postln();
+      return this;
+    };
+
+    spec.postc = function() {
+      this.asString().postc();
+      return this;
+    };
+
+    spec.postcln = function() {
+      this.asString().postcln();
+      return this;
+    };
+
     // TODO: implements postcs
     // TODO: implements totalFree
     // TODO: implements largestFreeBlock
diff --git a/src/sc/lang/classlib/Core/Object_test.js b/src/sc/lang/classlib/Core/Object_test.js
index 14ed89f..98ed7f2 100644
--- a/src/sc/lang/classlib/Core/Object_test.js
+++ b/src/sc/lang/classlib/Core/Object_test.js
@@ -92,14 +92,66 @@
     });
     it.skip("#dump", function() {
     });
-    it.skip("#post", function() {
-    });
-    it.skip("#postln", function() {
-    });
-    it.skip("#postc", function() {
-    });
-    it.skip("#postcln", function() {
-    });
+    it("#post", sinon.test(function() {
+      var instance, test;
+      var post;
+
+      post = this.spy();
+
+      instance = this.createInstance();
+      this.stub(instance, "asString", function() {
+        return { post: post };
+      });
+
+      test = instance.post();
+      expect(test).to.equal(instance);
+      expect(post).to.be.calledWith(undefined);
+    }));
+    it("#postln", sinon.test(function() {
+      var instance, test;
+      var postln;
+
+      postln = this.spy();
+
+      instance = this.createInstance();
+      this.stub(instance, "asString", function() {
+        return { postln: postln };
+      });
+
+      test = instance.postln();
+      expect(test).to.equal(instance);
+      expect(postln).to.be.calledWith(undefined);
+    }));
+    it("#postc", sinon.test(function() {
+      var instance, test;
+      var postc;
+
+      postc = this.spy();
+
+      instance = this.createInstance();
+      this.stub(instance, "asString", function() {
+        return { postc: postc };
+      });
+
+      test = instance.postc();
+      expect(test).to.equal(instance);
+      expect(postc).to.be.calledWith(undefined);
+    }));
+    it("#postcln", sinon.test(function() {
+      var instance, test;
+      var postcln;
+
+      postcln = this.spy();
+
+      instance = this.createInstance();
+      this.stub(instance, "asString", function() {
+        return { postcln: postcln };
+      });
+
+      test = instance.postcln();
+      expect(test).to.equal(instance);
+      expect(postcln).to.be.calledWith(undefined);
+    }));
     it.skip("#postcs", function() {
     });
     it.skip("#totalFree", function() {
diff --git a/src/sc/lang/io.js b/src/sc/lang/io.js
new file mode 100644
index 0000000..fccf533
--- /dev/null
+++ b/src/sc/lang/io.js
@@ -0,0 +1,24 @@
+(function(sc) {
+  "use strict";
+
+  require("./sc");
+
+  var io = {};
+
+  var SCScript = sc.SCScript;
+  var buffer   = "";
+
+  io.post = function(msg) {
+    var items;
+
+    items  = (buffer + msg).split("\n");
+    buffer = items.pop();
+
+    items.forEach(function(msg) {
+      SCScript.stdout(msg);
+    });
+  };
+
+  sc.lang.io = io;
+
+})(sc);
diff --git a/src/sc/lang/io_test.js b/src/sc/lang/io_test.js
new file mode 100644
index 0000000..21690e6
--- /dev/null
+++ b/src/sc/lang/io_test.js
@@ -0,0 +1,26 @@
+(function() {
+  "use strict";
+
+  require("./io");
+
+  var io = sc.lang.io;
+
+  describe("sc.lang.io", function() {
+    it("post", sinon.test(function() {
+      this.stub(sc.SCScript, "stdout");
+
+      io.post("abc");
+      expect(sc.SCScript.stdout).to.be.not.called;
+      sc.SCScript.stdout.reset();
+
+      io.post("d\n");
+      expect(sc.SCScript.stdout).to.be.calledWith("abcd");
+      sc.SCScript.stdout.reset();
+
+      io.post("abc\ndef\n");
+      expect(sc.SCScript.stdout).to.be.calledWith("abc");
+      expect(sc.SCScript.stdout).to.be.calledWith("def");
+      sc.SCScript.stdout.reset();
+    }));
+  });
+})();
diff --git a/src/sc/lang/klass/klass.js b/src/sc/lang/klass/klass.js
index e4811b4..4fd0af8 100644
--- a/src/sc/lang/klass/klass.js
+++ b/src/sc/lang/klass/klass.js
@@ -117,6 +117,7 @@
     newClass._Spec = constructor;
     constructor.prototype.__class = newClass;
     constructor.prototype.__Spec  = constructor;
+    constructor.prototype.__className = className;
 
     metaClass._Spec = constructor;
     metaClass._isMetaClass = true;
diff --git a/src/sc/sc.js b/src/sc/sc.js
index c163fbf..a9757bd 100644
--- a/src/sc/sc.js
+++ b/src/sc/sc.js
@@ -13,6 +13,16 @@
     installer(sc);
   };
 
+  // istanbul ignore next
+  SCScript.stdout = function(msg) {
+    console.log(msg);
+  };
+
+  // istanbul ignore next
+  SCScript.stderr = function(msg) {
+    console.error(msg);
+  };
+
   SCScript.VERSION = sc.VERSION;
 
   global.SCScript = sc.SCScript = SCScript;