diff --git a/c_expert/chapter7/cache.c b/c_expert/chapter7/cache.c
index e217648..e5a8c8f 100644
--- a/c_expert/chapter7/cache.c
+++ b/c_expert/chapter7/cache.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <string.h>
 
 #define DUMBCOPY for (i=0;i< 65536;i++) \
 						destination[i] = source[i]
diff --git a/c_expert/chapter7/singnal_test.c b/c_expert/chapter7/singnal_test.c
new file mode 100644
index 0000000..ff358ab
--- /dev/null
+++ b/c_expert/chapter7/singnal_test.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
+
+void handler(int s)
+{
+	if (s == SIGBUS) printf(" now got a bus error signal \n");
+	if (s == SIGSEGV) printf(" now got a segmentation violation signal \n");
+	if (s == SIGILL) printf(" now got a illegal instruction signal \n");
+	exit(1);
+}
+
+int main(void)
+{
+	printf("begin \n");
+	int *p = NULL;
+	signal(SIGBUS, handler);
+	signal(SIGSEGV, handler);
+	signal(SIGILL, handler);
+	*p = 0;
+	printf("end \n");
+}