diff --git a/eo-runtime/src/main/eo/org/eolang/const.eo b/eo-runtime/src/main/eo/org/eolang/const.eo
new file mode 100644
index 0000000000..6c9c67a71d
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+++ b/eo-runtime/src/main/eo/org/eolang/const.eo
@@ -0,0 +1,34 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2016-2024 Objectionary.com
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
++architect yegor256@gmail.com
++home https://github.com/objectionary/eo
++package org.eolang
++rt jvm org.eolang:eo-runtime:0.0.0
++version 0.0.0
+
+# Dataizes given `object`, makes new `bytes` from the data and behaves as given `bytes`.
+[object] > const
+  memory.alloc object > cached
+  # Object for using the cached one.
+  [] > make
+    ^.cached > @
diff --git a/eo-runtime/src/test/eo/org/eolang/const-tests.eo b/eo-runtime/src/test/eo/org/eolang/const-tests.eo
new file mode 100644
index 0000000000..c6b2204ffb
--- /dev/null
+++ b/eo-runtime/src/test/eo/org/eolang/const-tests.eo
@@ -0,0 +1,62 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2016-2024 Objectionary.com
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
++architect yegor256@gmail.com
++home https://github.com/objectionary/eo
++tests
++package org.eolang
++version 0.0.0
+
+# Test.
+[] > const-does-not-do-recalculation
+  memory.alloc 0 > m
+  # Func.
+  [] > func
+    ^.m.write (^.m.as-int.plus 1) > @
+  (const func).make > cached
+  seq > @
+    *
+      cached.as-int
+      cached.as-bytes
+      cached.as-bool
+      1.eq m
+
+# Test.
+[] > const-behaves-as-exclamationed
+  # Func.
+  [] > func
+    memory.alloc 0 > m
+    seq > @
+      *
+        TRUE
+        m.write (m.as-int.plus 1)
+  (const func).make > cached1
+  func > cached2!
+  seq > @
+    *
+      cached1
+      cached2
+      cached1
+      cached2
+      and.
+        cached1.eq cached2
+        1.eq cached1