diff --git a/threads/atomic/Makefile b/threads/atomic/Makefile
new file mode 100644
index 0000000..1f5c123
--- /dev/null
+++ b/threads/atomic/Makefile
@@ -0,0 +1,4 @@
+test : atomics.c
+	gcc atomics.c -o atomics
+clean:
+	rm atomics
diff --git a/threads/README.md b/threads/atomic/README.md
similarity index 100%
rename from threads/README.md
rename to threads/atomic/README.md
diff --git a/threads/atomic/atomics.c b/threads/atomic/atomics.c
new file mode 100644
index 0000000..38c9596
--- /dev/null
+++ b/threads/atomic/atomics.c
@@ -0,0 +1,164 @@
+/*
+ * measures the performance cost by time of using locks in multi-thread program
+ * Measure the overhead of calling lock and unlock depending on the level of contention
+ * by utilizing clock(), in time.h
+ * Author: Wenhui Zhang， Hu Yang, Pradeep
+ */
+
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <time.h>
+
+
+
+int ctr;
+pthread_mutex_t count_mutex;
+clock_t start_t, end_t;
+
+
+
+
+/* thread_lock: thread function for multi-thread generation */
+void thread_lock()
+{
+
+    for ( int i = 0; i < 10000; i++){
+        pthread_mutex_lock(&count_mutex);
+    
+        ctr = ctr + 1;
+        //printf("%d \n", ctr);
+    
+        pthread_mutex_unlock(&count_mutex);
+    }
+}
+
+
+/* thread_atomic: thread function for multi-thread generation */
+void thread_atomic()
+{
+
+    for ( int i = 0; i < 10000; i++){
+        __sync_add_and_fetch(&ctr, 1);
+        //printf("%d \n", ctr);
+    }
+
+}
+
+
+/* compare_and_swap: thread function for multi-thread generation */
+/*
+ void compare_and_swap()
+ {
+ 
+ pthread_mutex_lock(&count_mutex);
+ 
+ int oldvalue = 3;
+ int newvalue = 4;
+ int *ptr = &newvalue;
+ int temp = *ptr;
+ if(*ptr == oldvalue)
+ *ptr = newvalue;
+ 
+ pthread_mutex_unlock(&count_mutex);
+ 
+ }
+ */
+
+
+
+
+int atomic_comp(int num_threads)
+{
+    
+    
+    printf("Start of %d thread calculating...\n", num_threads);
+    double total_t_lock, total_t_unlock; //time counter
+    int rc;
+    int tnum; //counter for threads
+    pthread_mutex_init(&count_mutex, NULL); //initialize mutex
+    
+    
+    pthread_t  thread_info[num_threads];	// thread identifier
+    
+    /* Test for thread_incr_lock */
+    
+
+    start_t = clock();
+    for (tnum = 0; tnum < num_threads; tnum++){
+        //printf("create thread %d\n", tnum);
+        
+        rc = pthread_create(&thread_info[tnum], NULL, (void*)&thread_lock, NULL);
+        if (rc){
+            printf("ERROR; return code from pthread_create() is %d\n", rc);
+            exit(1);
+        }
+    }
+    
+    
+    for (tnum = 0; tnum < num_threads; tnum++){
+        pthread_join(thread_info[tnum], NULL);
+    }
+    
+    
+    end_t = clock();
+    
+    total_t_lock = (double)((end_t - start_t) / (double)CLOCKS_PER_SEC);
+    printf("Total time cost by running %d threads for increase function with lock implementation: %f\n sec", num_threads, total_t_lock);
+    
+   
+    
+    /* Test for thread_atomic */
+    
+    ctr = 0;
+    
+    
+    start_t = clock();
+    for (tnum = 0; tnum < num_threads; tnum++){
+        //printf("create thread %d\n", tnum);
+        
+        rc = pthread_create(&thread_info[tnum], NULL, (void*)&thread_atomic, NULL);
+        if (rc){
+            printf("ERROR; return code from pthread_create() is %d\n", rc);
+            exit(1);
+        }
+    }
+    
+    
+    for (tnum = 0; tnum < num_threads; tnum++){
+        pthread_join(thread_info[tnum], NULL);
+    }
+    
+    end_t = clock();
+    
+    total_t_unlock = (double)( (end_t - start_t) / (double)CLOCKS_PER_SEC);
+    printf("Total time cost by running %d threads for increase function with atomic: %f sec\n", num_threads, total_t_unlock);
+    
+    
+    
+    printf("Mutex Time Cost Against Atomic by running %d threads for increase function: %f sec\n", num_threads, total_t_lock - total_t_unlock);
+    
+    
+    printf("Per thread Mutex Time Cost Against Atomic by running %d threads for increase function: %f sec\n", num_threads, (total_t_lock - total_t_unlock)/(double)num_threads);
+    
+    printf("End of %d thread calculating...\n", num_threads);
+    
+    return 0;
+}
+
+
+
+int main(void)
+{
+    printf("------------------------\n");
+    atomic_comp(16);
+    printf("------------------------\n");
+    atomic_comp(1);
+    printf("------------------------\n");
+    atomic_comp(160);
+    
+    return 0;
+    
+}
diff --git a/threads/atomic/output_atomics b/threads/atomic/output_atomics
new file mode 100644
index 0000000..4042f99
--- /dev/null
+++ b/threads/atomic/output_atomics
@@ -0,0 +1,22 @@
+wenhui-2:threads WenhuiZhang$ ./atomics 
+------------------------
+Start of 16 thread calculating...
+Total time cost by running 16 threads for increase function with lock implementation: 0.680011
+ secTotal time cost by running 16 threads for increase function with atomic: 0.016044 sec
+Mutex Time Cost Against Atomic by running 16 threads for increase function: 0.663967 sec
+Per thread Mutex Time Cost Against Atomic by running 16 threads for increase function: 0.041498 sec
+End of 16 thread calculating...
+------------------------
+Start of 1 thread calculating...
+Total time cost by running 1 threads for increase function with lock implementation: 0.000611
+ secTotal time cost by running 1 threads for increase function with atomic: 0.000132 sec
+Mutex Time Cost Against Atomic by running 1 threads for increase function: 0.000479 sec
+Per thread Mutex Time Cost Against Atomic by running 1 threads for increase function: 0.000479 sec
+End of 1 thread calculating...
+------------------------
+Start of 160 thread calculating...
+Total time cost by running 160 threads for increase function with lock implementation: 7.917729
+ secTotal time cost by running 160 threads for increase function with atomic: 0.159848 sec
+Mutex Time Cost Against Atomic by running 160 threads for increase function: 7.757881 sec
+Per thread Mutex Time Cost Against Atomic by running 160 threads for increase function: 0.048487 sec
+End of 160 thread calculating...