diff --git a/c04_string/defines.c b/c04_string/defines.c
new file mode 100644
index 0000000..bfd7b36
--- /dev/null
+++ b/c04_string/defines.c
@@ -0,0 +1,18 @@
+/* defines.c - 使用limits.h和float头文件中定义的明示常量 */
+#include <stdio.h>
+#include <limits.h>
+#include <float.h>
+
+int main(void)
+{
+    printf("Some number limits for this system:\n");
+    printf("Biggest int; %d\n", INT_MAX);
+    printf("Smallest long long: %lld\n", LLONG_MIN);
+    printf("One byte = %d bits on this system.\n", CHAR_BIT);
+    printf("Largest double: %e\n", DBL_MAX);
+    printf("Smallest normal float: %e\n", FLT_MIN);
+    printf("float precision = %d digits\n", FLT_DIG);
+    printf("float epsilon = %e\n", FLT_EPSILON);
+    
+    return 0;
+}
\ No newline at end of file