diff --git a/concurrency-mapreduce/README.md b/concurrency-mapreduce/README.md
index 252e791..0cfa98d 100644
--- a/concurrency-mapreduce/README.md
+++ b/concurrency-mapreduce/README.md
@@ -90,8 +90,9 @@ infrastructure does the rest.
 
 ## Code Overview
 
-We give you here `mapreduce.h` file that specifies exactly what you must build
-in your MapReduce library:
+We give you here the
+[`mapreduce.h`](https://github.com/remzi-arpacidusseau/ostep-projects/tree/master/concurrency-mapreduce/mapreduce.h)
+header file that specifies exactly what you must build in your MapReduce library:
 
 ```
 #ifndef __mapreduce_h__
diff --git a/concurrency-mapreduce/mapreduce.h b/concurrency-mapreduce/mapreduce.h
new file mode 100644
index 0000000..49c2cdc
--- /dev/null
+++ b/concurrency-mapreduce/mapreduce.h
@@ -0,0 +1,19 @@
+#ifndef __mapreduce_h__
+#define __mapreduce_h__
+
+typedef char *(*Getter)();
+
+typedef void (*Mapper)(char *file_name);
+typedef void (*Reducer)(char *key, Getter get_func, int partition_number);
+typedef unsigned long (*Partitioner)(char *key, int num_buckets);
+
+void MR_Emit(char *key, char *value);
+
+unsigned long MR_DefaultHashPartition(char *key, int num_buckets);
+
+void MR_Run(int argc, char *argv[], 
+	    Mapper map, int num_mappers, 
+	    Reducer reduce, int num_reducers, 
+	    Partitioner partition);
+
+#endif // __mapreduce_h__