diff --git a/c04_string/pizza.c b/c04_string/pizza.c
new file mode 100644
index 0000000..416af54
--- /dev/null
+++ b/c04_string/pizza.c
@@ -0,0 +1,18 @@
+/* pizza.c - 在比萨程序中使用已定义的常量 */
+#include <stdio.h>
+
+#define PI 3.14159265359
+
+int main(void)
+{
+    float area, circum, radius;
+
+    printf("What is the radius of your pizza?\n");
+    scanf("%f", &radius);
+    area = PI * radius * radius;
+    circum = 2.0 * PI * radius;
+    printf("Your basic pizza parameters are as follows:\n");
+    printf("circumference = %1.2f, area = %1.2f\n", circum, area);
+
+    return 0;
+}
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