diff --git a/2207/C语言同步练习源码/5.指针-3.c b/2207/C语言同步练习源码/5.指针-3.c
new file mode 100644
index 0000000..2c1e7f3
--- /dev/null
+++ b/2207/C语言同步练习源码/5.指针-3.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+int main(){
+	char str[] = "AbcDEfg";
+	char *p = str;
+	
+	while(*p != '\0'){
+		if(*p >= 'a' && *p <= 'z'){
+			*p -= 32;
+		}else{
+			*p += 32;
+		}
+		p++;
+	}
+	puts(str);
+
+	return 0;
+}
+
diff --git a/2207/C语言同步练习答案.md b/2207/C语言同步练习答案.md
index 15a4f74..b3b7d24 100644
--- a/2207/C语言同步练习答案.md
+++ b/2207/C语言同步练习答案.md
@@ -808,6 +808,28 @@ int main(){
 
 ![image-20250227231232971](https://yp.smallkun.cn/markdown/image-20250227231232971.png!compress)
 
+```c
+#include <stdio.h>
+
+int main(){
+	char str[] = "AbcDEfg";
+	char *p = str;
+	
+	while(*p != '\0'){
+		if(*p >= 'a' && *p <= 'z'){
+			*p -= 32;
+		}else{
+			*p += 32;
+		}
+		p++;
+	}
+	puts(str);
+
+	return 0;
+}
+
+```
+
 
 
 ### 指针-4