diff --git a/builtin.c b/builtin.c
index 7e3e604..7541be3 100644
--- a/builtin.c
+++ b/builtin.c
@@ -2,7 +2,7 @@
  * @Author: 1ridic 
  * @Date: 2022-09-18 14:16:19 
  * @Last Modified by: 1ridic
- * @Last Modified time: 2022-09-18 14:28:01
+ * @Last Modified time: 2022-09-18 14:52:17
  */
 #include <stdio.h>
 #include <stdlib.h>
@@ -12,17 +12,20 @@
 int dish_cd(char **args);
 int dish_help(char **args);
 int dish_exit(char **args);
+int dish_clear(char **args);
 
 char* builtin_cmd[] = {
   "cd",
   "help",
-  "exit"
+  "exit",
+  "clear"
 };
 
 int (*builtin_func[]) (char **) = {
   &dish_cd,
   &dish_help,
-  &dish_exit
+  &dish_exit,
+  &dish_clear
 };
 
 int dish_cd(char **args)
@@ -50,4 +53,9 @@ int dish_exit(char **args)
 
 int getBuiltinNum() {
   return sizeof(builtin_cmd) / sizeof(char *);
+}
+
+int dish_clear(char **args){
+  fprintf(stdout,"\033[H\033[J");
+  return 0;
 }
\ No newline at end of file
diff --git a/main.c b/main.c
index 23b4e4b..fab2f99 100644
--- a/main.c
+++ b/main.c
@@ -2,7 +2,7 @@
  * @Author: 1ridic 
  * @Date: 2022-09-18 14:13:59 
  * @Last Modified by: 1ridic
- * @Last Modified time: 2022-09-18 14:21:48
+ * @Last Modified time: 2022-09-18 14:53:04
  */
 #include <signal.h>
 #include <stdio.h>
@@ -14,17 +14,18 @@ char volatile isWaiting = 0;
 void intHandler(int dummy) {
   if (isWaiting) {
     return;
-  printf("\nSIGINT exit.\n");
+  fprintf(stderr,"\nSIGINT exit.\n");
   exit(EXIT_FAILURE);
   }
 }
 
 int main(int argc, char *argv[]) {
-
+  /* soft irq */
   signal(SIGINT, intHandler);
-
+  /* clear screen */
+  fprintf(stdout,"\033[H\033[J");
 #ifdef DEBUG
-  printf("DEBUG is defined\n");
+  fprintf(stdout,"DEBUG is defined\n");
 #endif
   while (1) {
     loop();