diff --git a/c04_string/floatcnv.c b/c04_string/floatcnv.c
new file mode 100644
index 0000000..d087f08
--- /dev/null
+++ b/c04_string/floatcnv.c
@@ -0,0 +1,18 @@
+/* floatcnv.c - 不匹配的浮点型转换 */
+// 在gcc version 10.2.1 20210110 (Debian 10.2.1-6)环境下
+// 执行结果与教程P89中的结果不一样
+#include <stdio.h>
+
+int main(void)
+{
+    float n1 = 3.0;
+    float n2 = 3.0;
+    long n3 = 2000000000;
+    long n4 = 1234567890;
+
+    printf("%.1e %.1e %.1e %.1e\n", n1, n2, n3, n4);
+    printf("%ld %ld\n", n3, n4);
+    printf("%ld %ld %ld %ld\n", n1, n2, n3, n4);
+
+    return 0;
+}
\ No newline at end of file