diff --git a/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java b/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
new file mode 100644
index 0000000..bc70e9b
--- /dev/null
+++ b/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2017 Volker Berlin (i-net software)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package de.inetsoftware.jwebassembly.binary;
+
+/**
+ * Instruction opcodes of the binary WebAssembly format.
+ * 
+ * @author Volker Berlin
+ *
+ */
+interface InstructionOpcodes {
+
+    static final int RETURN    = 0x0F;
+
+    static final int GET_LOCAL = 0x20;
+
+    static final int SET_LOCAL = 0x21;
+
+    static final int I32_CONST = 0x41;
+
+    static final int I32_ADD   = 0x6A;
+
+}
diff --git a/src/de/inetsoftware/jwebassembly/binary/SectionType.java b/src/de/inetsoftware/jwebassembly/binary/SectionType.java
new file mode 100644
index 0000000..5b4ed71
--- /dev/null
+++ b/src/de/inetsoftware/jwebassembly/binary/SectionType.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2017 Volker Berlin (i-net software)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package de.inetsoftware.jwebassembly.binary;
+
+/**
+ * @author Volker Berlin
+ */
+enum SectionType {
+    Custom, //   0
+    Type, //     1   Function signature declarations
+    Import, //   2   Import declarations
+    Function, // 3   Function declarations
+    Table, //    4   Indirect function table and other tables
+    Memory, //   5   Memory attributes
+    Global, //   6   Global declarations
+    Export, //   7   Exports
+    Start, //    8   Start function declaration
+    Element, //  9   Elements section
+    Code, //    10  Function bodies (code)
+    Data, //    11  Data segments
+}
diff --git a/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java b/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java
new file mode 100644
index 0000000..b573462
--- /dev/null
+++ b/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java
@@ -0,0 +1,102 @@
+/*
+ * Copyright 2017 Volker Berlin (i-net software)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package de.inetsoftware.jwebassembly.binary;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import javax.annotation.Nonnegative;
+
+/**
+ * @author Volker Berlin
+ */
+class WasmOutputStream extends ByteArrayOutputStream {
+
+    /**
+     * Write a integer little endian (ever 4 bytes)
+     * 
+     * @param value
+     *            the value
+     */
+    void writeInt32( int value ) {
+        write( (value >>> 0) & 0xFF );
+        write( (value >>> 8) & 0xFF );
+        write( (value >>> 16) & 0xFF );
+        write( (value >>> 24) & 0xFF );
+    }
+
+    /**
+     * Write an unsigned integer.
+     * 
+     * @param value
+     *            the value
+     */
+    void writeVaruint32( @Nonnegative int value ) {
+        do {
+            int b = value & 0x7F; // low 7 bits
+            value >>= 7;
+            if( value != 0 ) { /* more bytes to come */
+                b |= 0x80;
+            }
+            write( b );
+        } while( value != 0 );
+    }
+
+    /**
+     * Write an integer value.
+     * 
+     * @param value
+     *            the value
+     */
+    void writeVarint32( int value ) {
+        while( true ) {
+            int b = value & 0x7F;
+            value >>= 7;
+
+            /* sign bit of byte is second high order bit (0x40) */
+            if( (value == 0 && (b & 0x40) == 0) || (value == -1 && (b & 0x40) != 0) ) {
+                write( b );
+                return;
+            } else {
+                write( b | 0x80 );
+            }
+        }
+    }
+
+    /**
+     * Write a section header.
+     * 
+     * @param type
+     *            the name of the section
+     * @param dataSize
+     *            the size of the data
+     * @param name
+     *            the name, must be set if the id == 0
+     * @throws IOException
+     *             if any I/O error occur
+     */
+    void writeSectionHeader( SectionType type, int dataSize, String name ) throws IOException {
+        writeVaruint32( type.ordinal() );
+        writeVaruint32( dataSize );
+        if( type == SectionType.Custom ) {
+            byte[] bytes = name.getBytes( StandardCharsets.ISO_8859_1 );
+            writeVaruint32( bytes.length );
+            write( bytes );
+        }
+    }
+
+}