diff --git a/Makefile b/Makefile
index cac799d..e4d4d19 100644
--- a/Makefile
+++ b/Makefile
@@ -154,6 +154,9 @@ UPROGS=\
 	$U/_grind\
 	$U/_wc\
 	$U/_zombie\
+	$U/_sleep\
+	$U/_pingpong\
+	$U/_find
 
 
 ifeq ($(LAB),syscall)
diff --git a/kernel/main.c b/kernel/main.c
index 8a3dc2e..06aea69 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -10,6 +10,7 @@ volatile static int started = 0;
 void main() {
   if (cpuid() == 0) {
     // consoleinit();
+    printf("[200110609] enter main, init kernel\n");
     // printfinit();
     printf("\n");
     printf("xv6 kernel is booting\n");
diff --git a/kernel/proc.c b/kernel/proc.c
index 1607145..9354a3e 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -183,6 +183,7 @@ uchar initcode[] = {0x17, 0x05, 0x00, 0x00, 0x13, 0x05, 0x45, 0x02, 0x97, 0x05,
 
 // Set up first user process.
 void userinit(void) {
+  printf("[200110609] enter userinit\n");
   struct proc *p;
 
   p = allocproc();
@@ -197,6 +198,7 @@ void userinit(void) {
   p->trapframe->epc = 0;      // user program counter
   p->trapframe->sp = PGSIZE;  // user stack pointer
 
+  printf("[200110609] copy initcode to first user process\n");
   safestrcpy(p->name, "initcode", sizeof(p->name));
   p->cwd = namei("/");
 
diff --git a/kernel/start.c b/kernel/start.c
index f704fee..792eb99 100644
--- a/kernel/start.c
+++ b/kernel/start.c
@@ -52,8 +52,8 @@ void start() {
     // init uart and printf
     consoleinit();
     printfinit();
+    printf("[200110609] in start, init driver, interrupts and change mode\n");
   }
-
   // switch to supervisor mode and jump to main().
   asm volatile("mret");
 }
diff --git a/user/find.c b/user/find.c
new file mode 100644
index 0000000..959c453
--- /dev/null
+++ b/user/find.c
@@ -0,0 +1,81 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fs.h"
+
+void find(char *path, char *fName);
+
+// 在目录树中查找名称与字符串匹配的所有文件，输出文件的相对路径。
+// 命令格式：find path file_name
+int main(int argc,char* argv[]){
+    if (argc != 3){
+        printf("usage:find dirName fileName");
+        exit(1);
+    }
+    find(argv[1],argv[2]);
+    exit(0);
+}
+
+// 关键的查找函数
+void find(char *path, char *fName){
+    char buffer[512], *p;
+    int fd;
+    struct dirent de;
+    struct stat st;
+
+    if((fd = open(path, 0)) < 0){        // 首先打开文件
+        fprintf(2, "find: cannot open %s\n", path);
+        return;
+    }
+    if(fstat(fd, &st) < 0){     // 获取文件描述符的信息
+        printf("find: cannot stat %s\n", path);
+        close(fd);
+        return;
+    }
+
+    if (st.type != T_DIR){              // 检测输入的dir是否为目录
+        printf("find:%s is not a directory\n", path);
+        close(fd);
+        return;
+    }
+
+    if(strlen(path) + 1 + DIRSIZ + 1 > sizeof buffer){     // 判断路径长度是否符合要求
+        printf("find: directory too long\n");
+        close(fd);
+        return;
+    }
+
+    strcpy(buffer,path);        // 复制path到buffer
+    p = buffer + strlen(buffer);  // 将p指针指向buffer的最后一位
+    *p = '/';               // 将最后一位字符赋值为‘/’
+    p++;                    // 指针指向下一位，用来接收之后的信息
+    // 从文件描述符（fd）对应的文件中读取数据，写到de中
+    while(read(fd, &de, sizeof(de)) == sizeof(de)){         // 读取目录下的信息
+        if(de.inum == 0)
+            continue;
+
+        // strcmp()，当两个字符串相等时，返回0
+        if(!strcmp(de.name,".") || !strcmp(de.name,"..")){  // 不要递归'.','..'
+            continue;
+        }
+
+        // memmove()，将de.name移动到p的位置
+        memmove(p, de.name, DIRSIZ);
+        p[DIRSIZ] = 0;  // 在缓冲区buffer的末尾添加一个空字符，以确保字符串以空字符结尾。
+        if(stat(buffer, &st) < 0){
+            printf("find: cannot stat %s\n", buffer);
+            continue;
+        }
+        switch(st.type){                    // 判断读入的信息为目录还是文件
+            case T_FILE:
+                if(!strcmp(de.name,fName)){
+                    printf("%s\n",buffer);
+                }
+                break;
+            case T_DIR:
+                find(buffer,fName);
+                break;
+        }
+    }
+    close(fd);
+}
\ No newline at end of file
diff --git a/user/init.c b/user/init.c
index 9ca8790..02f3d65 100644
--- a/user/init.c
+++ b/user/init.c
@@ -23,13 +23,14 @@ int main(void) {
 
   for (;;) {
     printf("init: starting sh\n");
+    printf("[200110609] start sh through execve\n");
     pid = fork();
     if (pid < 0) {
       printf("init: fork failed\n");
       exit(1);
     }
     if (pid == 0) {
-      exec("sh", argv);
+      exec("sh", argv); // 子进程执行shell程序，且不会返回此调用进程
       printf("init: exec sh failed\n");
       exit(1);
     }
diff --git a/user/pingpong.c b/user/pingpong.c
new file mode 100644
index 0000000..bb96f26
--- /dev/null
+++ b/user/pingpong.c
@@ -0,0 +1,53 @@
+#include "kernel/types.h"
+#include "user.h"   // 导入xv6自带的库函数
+
+int main(int argc,char* argv[]){
+    int p1[2], p2[2];
+    pipe(p1);
+    pipe(p2);
+    char buffer[4];
+    int size = 4;
+    // 管道创建完成之后，0为读，1为写
+
+    // // 方法一：使用两个pipe管道
+    // // 创建子进程
+    // if(fork() == 0){
+    //     // 子进程，fork()返回0
+    //     close(p1[1]);   // 关闭子进程p1写端
+    //     read(p1[0], buffer, size);  // 读取
+    //     printf("%d: received %s\n", getpid(),buffer);
+    //     close(p1[0]);
+
+    //     close(p2[0]);   // 关闭子进程p2读端
+    //     write(p2[1], "pong", strlen("pong"));   // 写入
+    //     close(p2[1]);
+    //     exit(0);
+    // }else{
+    //     // 父进程，fork()返回子进程的pid
+    //     close(p1[0]);   // 关闭父进程p1读端
+    //     write(p1[1], "ping", strlen("ping"));   // 写入
+    //     close(p1[1]);
+
+    //     close(p2[1]);
+    //     read(p2[0], buffer, size);
+    //     printf("%d: received %s\n", getpid(),buffer);
+    //     close(p2[0]);
+    //     exit(0);
+    // }
+
+    // 方法二：使用一个pipe管道
+    // 创建子进程
+    if(fork() == 0){
+        read(p1[0],buffer,size);
+        printf("%d: received %s\n", getpid(),buffer);
+        write(p1[1],"pong",strlen("pong"));
+        exit(0);
+    }
+    else{
+        write(p1[1],"ping",strlen("ping"));
+        wait(0);     // 等待子进程完成读写操作
+        read(p1[0],buffer,size);
+        printf("%d: received %s\n",getpid(),buffer);
+        exit(0);
+    }
+}
\ No newline at end of file
diff --git a/user/sleep.c b/user/sleep.c
new file mode 100644
index 0000000..76ef77b
--- /dev/null
+++ b/user/sleep.c
@@ -0,0 +1,13 @@
+#include "kernel/types.h"
+#include "user.h"   // 导入xv6自带的库函数
+
+int main(int argc,char* argv[]){
+    if(argc != 2){
+        printf("Sleep needs one argument!\n"); //检查参数数量是否正确
+        exit(-1);
+    }
+    int ticks = atoi(argv[1]); //将字符串参数转为整数
+    sleep(ticks);              //使用系统调用sleep
+    printf("(nothing happens for a little while)\n");
+    exit(0); //确保进程退出
+}
\ No newline at end of file