添加注释

base/extend/dma.cpp

@@ -39,6 +39,7 @@ std::ostream &operator<<(std::ostream &os, const baseDMA &rs) {
 }
 
 lacksDMA::lacksDMA(const char *c, const char *l, int r) : baseDMA(l, r) {
+    //strncpy用于字符串复制
     std::strncpy(color, c, 39);
     color[39] = '\0';
 }