diff --git a/include/console.h b/include/console.h
index 783ca48..0880731 100644
--- a/include/console.h
+++ b/include/console.h
@@ -13,7 +13,7 @@
 
 #ifndef	_ORANGES_CONSOLE_H_
 #define	_ORANGES_CONSOLE_H_
-
+#include "const.h"
 
 /* CONSOLE */
 typedef struct s_console
@@ -30,12 +30,18 @@ typedef struct s_console
 #define SCR_UP	1	/* scroll upward */
 #define SCR_DN	-1	/* scroll downward */
 
-#define SCR_SIZE		(80 * 25)
-#define SCR_WIDTH		 80
-
-#define DEFAULT_CHAR_COLOR	(MAKE_COLOR(BLACK, WHITE))
-#define GRAY_CHAR		(MAKE_COLOR(BLACK, BLACK) | BRIGHT)
-#define RED_CHAR		(MAKE_COLOR(BLUE, RED) | BRIGHT)
+#define SCR_WIDTH 80
+#define SCR_HEIGHT 25
+#define SCR_SIZE (SCR_HEIGHT * SCR_WIDTH)
+#define SCR_BUFSIZE (2 * SCR_SIZE)
+#define SCR_MAXLINE (SCR_BUFSIZE / SCR_WIDTH)
 
+#define FLASH_CHAR 0x8000
+#define DEFAULT_CHAR_COLOR ((MAKE_COLOR(BLACK, WHITE | BRIGHT)) << 8)
+#define GRAY_CHAR (MAKE_COLOR(BLACK, BLACK) | BRIGHT)
+#define RED_CHAR (MAKE_COLOR(BLUE, RED) | BRIGHT)
+#define WHITE_CHAR (MAKE_COLOR(BLACK, WHITE | BRIGHT))
+#define MAKE_CELL(clr, ch) (clr | ch)
+#define BLANK MAKE_CELL(DEFAULT_CHAR_COLOR, ' ')
 
 #endif /* _ORANGES_CONSOLE_H_ */
\ No newline at end of file
diff --git a/include/const.h b/include/const.h
index 284d050..6b28b0d 100644
--- a/include/const.h
+++ b/include/const.h
@@ -165,6 +165,7 @@
 //added by mingxuan 2019-5-19
 #define	CRTC_ADDR_REG	0x3D4	/* CRT Controller Registers - Addr Register */
 #define	CRTC_DATA_REG	0x3D5	/* CRT Controller Registers - Data Register */
+#define UNDERLINE_REG 0x14	 /* reg index of underline */
 #define	START_ADDR_H	0xC	/* reg index of video mem start addr (MSB) */
 #define	START_ADDR_L	0xD	/* reg index of video mem start addr (LSB) */
 #define	CURSOR_H	0xE	/* reg index of cursor position (MSB) */
diff --git a/include/global.h b/include/global.h
index 096d287..11d5ead 100644
--- a/include/global.h
+++ b/include/global.h
@@ -12,7 +12,6 @@ extern int		kernel_initial;
 
 extern int		ticks;
 
-extern int		disp_pos;
 extern u8		gdt_ptr[6];	// 0~15:Limit  16~47:Base
 extern DESCRIPTOR	gdt[GDT_SIZE];
 extern u8		idt_ptr[6];	// 0~15:Limit  16~47:Base
diff --git a/include/proto.h b/include/proto.h
index f4379c3..6d03253 100644
--- a/include/proto.h
+++ b/include/proto.h
@@ -6,10 +6,12 @@
 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
 
 /* klib.asm */
-void	disp_str(char* info);
-void	disp_int(int input);
-void	disp_color_str(char* info, int color);
-void write_char(char ch);    //added by mingxuan 2019-5-19
+
+void vga_set_disppos(int new_pos);
+int vga_get_disppos();
+void vga_write_char(const char ch, u8 color);
+void vga_write_str(const char * str);
+void vga_write_str_color(const char * str, u8 color);
 
 //added by zcr
 void	disable_irq(int irq);
@@ -22,7 +24,6 @@ void	init_prot();
 u32	seg2phys(u16 seg);
 
 /* klib.c */
-void	delay(int time);
 
 /* kernel.asm */
 u32  read_cr2();			//add by visual 2016.5.9
diff --git a/include/tty.h b/include/tty.h
index fae4111..7c75613 100644
--- a/include/tty.h
+++ b/include/tty.h
@@ -13,7 +13,7 @@
 
 #ifndef	_ORANGES_TTY_H_
 #define	_ORANGES_TTY_H_
-
+#include "type.h"
 
 #define TTY_IN_BYTES		256	/* tty input queue size */
 #define TTY_OUT_BUF_LEN		2	/* tty output buffer size */
diff --git a/include/uart.h b/include/uart.h
new file mode 100644
index 0000000..4f8dd50
--- /dev/null
+++ b/include/uart.h
@@ -0,0 +1,12 @@
+#ifndef UART_H
+#define UART_H
+
+#define PORT 0x3f8          // COM1
+#define SERIAL_BUF_SIZE 256
+
+
+int init_serial();
+char read_serial();
+void write_serial(char a);
+
+#endif
\ No newline at end of file
diff --git a/kernel/Makefrag b/kernel/Makefrag
index 9efc253..5a36de5 100644
--- a/kernel/Makefrag
+++ b/kernel/Makefrag
@@ -30,8 +30,7 @@ KERN_SRCFILES :=kernel/kernel.asm	\
 		kernel/i8259.c	\
 		kernel/testfunc.c	\
 		kernel/protect.c	\
-		lib/klib.c		\
-		lib/kliba.asm		\
+		kernel/uart.c	\
 
 
 KERN_OBJFILES	:= $(patsubst %.c, $(OBJDIR)/%.o, $(KERN_SRCFILES))
diff --git a/kernel/console.c b/kernel/console.c
index 380c45d..d4138c5 100644
--- a/kernel/console.c
+++ b/kernel/console.c
@@ -48,7 +48,7 @@ void init_screen(TTY* tty)
 	tty->console->current_line = 0;
 
 	if(nr_tty==0){
-		tty->console->cursor = disp_pos / 2;
+		tty->console->cursor = vga_get_disppos();
 	}
 	const char prompt[] = "[TTY #?]\n";
 
@@ -87,15 +87,15 @@ void out_char(CONSOLE* con, char ch)
 			con->cursor--;
 			//*(pch - 2) = ' ';
 			//*(pch - 1) = DEFAULT_CHAR_COLOR;
-			disp_pos = con->cursor*2;
-			write_char(' ');
+			vga_set_disppos(con->cursor);
+			vga_write_char(' ', WHITE_CHAR);
 		}
 		break;
 	default:
 		//*pch++ = ch;
 		//*pch++ = DEFAULT_CHAR_COLOR;
-		disp_pos = con->cursor*2;
-		write_char(ch);
+		vga_set_disppos(con->cursor);
+		vga_write_char(ch, WHITE_CHAR);
 		con->cursor++;
 		
 		break;
@@ -144,7 +144,7 @@ static void clear_screen(int pos, int len)
 	u8 * pch = (u8*)K_PHY2LIN(V_MEM_BASE + pos * 2);
 	while (--len >= 0) {
 		*pch++ = ' ';
-		*pch++ = DEFAULT_CHAR_COLOR;
+		*pch++ = (u8)DEFAULT_CHAR_COLOR;
 	}
 }
 
diff --git a/kernel/exec.c b/kernel/exec.c
index 034f926..d47fea1 100644
--- a/kernel/exec.c
+++ b/kernel/exec.c
@@ -35,7 +35,7 @@ u32 sys_exec(char *path)
 
 	if( 0==path )
 	{
-		disp_color_str("exec: path ERROR!",0x74);
+		vga_write_str_color("exec: path ERROR!",0x74);
 		return -1;
 	}
 	
@@ -86,7 +86,7 @@ u32 sys_exec(char *path)
 
 		if( err_temp!=0 )
 		{
-			disp_color_str("kernel_main Error:lin_mapping_phy",0x74);
+			vga_write_str_color("kernel_main Error:lin_mapping_phy",0x74);
 			return -1;
 		}
 	}
@@ -98,9 +98,9 @@ u32 sys_exec(char *path)
 	if (Echo_Phdr != NULL)
 		sys_free(Echo_Phdr);
 
-	//disp_color_str("\n[exec success:",0x72);//灰底绿字
-	//disp_color_str(path,0x72);//灰底绿字	
-	//disp_color_str("]",0x72);//灰底绿字
+	//vga_write_str_color("\n[exec success:",0x72);//灰底绿字
+	//vga_write_str_color(path,0x72);//灰底绿字	
+	//vga_write_str_color("]",0x72);//灰底绿字
 	return 0;
 }
 
@@ -157,7 +157,7 @@ static u32 exec_load(u32 fd,const Elf32_Ehdr* Echo_Ehdr,const Elf32_Phdr Echo_Ph
 	
 	if( 0==Echo_Ehdr->e_phnum )
 	{
-		disp_color_str("exec_load: elf ERROR!",0x74);
+		vga_write_str_color("exec_load: elf ERROR!",0x74);
 		return -1;
 	}
 
@@ -183,7 +183,7 @@ static u32 exec_load(u32 fd,const Elf32_Ehdr* Echo_Ehdr,const Elf32_Phdr Echo_Ph
 		}
 		else 
 		{
-			disp_color_str("exec_load: unKnown elf'program!",0x74);
+			vga_write_str_color("exec_load: unKnown elf'program!",0x74);
 			return -1;
 		}
 	}
diff --git a/kernel/fat32.c b/kernel/fat32.c
index 19559b7..124e24a 100644
--- a/kernel/fat32.c
+++ b/kernel/fat32.c
@@ -179,7 +179,7 @@ STATE ReadFile(int fd,void *buf, int length)
 		return ACCESSDENIED;
 	}
 	
-	disp_str("read:");
+	kprintf("read:");
 	if(pfile->off>=pfile->size)
 	{
 		return 0;
@@ -351,8 +351,8 @@ STATE OpenFile(const char *filename,int mode)
 	GetNameFromPath(fullpath,name);
 
 	state=PathToCluster(parent,&parentCluster);
-	disp_str("\nstate=");
-	disp_int(state);
+	kprintf("\nstate=");
+	kprintf("%d", state);
 	if(state!=OK)
 	{
 		return -1;
@@ -364,7 +364,7 @@ STATE OpenFile(const char *filename,int mode)
 	{
 		if(state == NAMEEXIST) //文件存在，使用O_CREAT是多余的，继续执行OpenFile即可
 		{
-			disp_str("file exists, O_CREAT is no use!");
+			kprintf("file exists, O_CREAT is no use!");
 		}
 		else //文件不存在，需要使用O_CREAT，先创建文件，再执行OpenFile
 		{
@@ -376,7 +376,7 @@ STATE OpenFile(const char *filename,int mode)
 	{
 		if(state != NAMEEXIST) //文件不存在，需要使用O_CREAT，用户没有使用，则报错并返回-1，表示路径有误
 		{
-			disp_str("no file, use O_CREAT!");
+			kprintf("no file, use O_CREAT!");
 			return -1;
 		}
 		else{} //文件存在，使用O_CREAT是多余的，继续执行OpenFile即可
@@ -384,11 +384,11 @@ STATE OpenFile(const char *filename,int mode)
 	//~mingxuan 2019-5-19
 
 	state=ReadRecord(parentCluster,name,&record,NULL,NULL);
-	disp_str("state=");
-	disp_int(state);
+	kprintf("state=");
+	kprintf("%d", state);
 	if(state!=OK)
 	{
-		disp_str("ReadRecord Fail!");
+		kprintf("ReadRecord Fail!");
 		return -1;
 	}
 	
@@ -403,9 +403,9 @@ STATE OpenFile(const char *filename,int mode)
 
     if ((fd < 0) || (fd >= NR_FILES)) {
 		// panic("filp[] is full (PID:%d)", proc2pid(p_proc_current));
-		disp_str("filp[] is full (PID:");
-		disp_int(proc2pid(p_proc_current));
-		disp_str(")\n");
+		kprintf("filp[] is full (PID:");
+		kprintf("%d", proc2pid(p_proc_current));
+		kprintf(")\n");
 		return -1;
     }
 
@@ -414,9 +414,9 @@ STATE OpenFile(const char *filename,int mode)
 		if ((f_desc_table[i].flag == 0))
 			break;
 	if (i >= NR_FILE_DESC) {
-		disp_str("f_desc_table[] is full (PID:");
-		disp_int(proc2pid(p_proc_current));
-		disp_str(")\n");
+		kprintf("f_desc_table[] is full (PID:");
+		kprintf("%d", proc2pid(p_proc_current));
+		kprintf(")\n");
 		return -1;
 	}
 	
@@ -428,9 +428,9 @@ STATE OpenFile(const char *filename,int mode)
 		if (f_desc_table_fat[i].flag == 0)
 			break;
 	if (i >= NR_FILE_DESC) {
-		disp_str("f_desc_table[] is full (PID:");
-		disp_int(proc2pid(p_proc_current));
-		disp_str(")\n");
+		kprintf("f_desc_table[] is full (PID:");
+		kprintf("%d", proc2pid(p_proc_current));
+		kprintf(")\n");
 	}
 
 	//以下是给File结构体赋值
@@ -442,9 +442,9 @@ STATE OpenFile(const char *filename,int mode)
 	f_desc_table_fat[i].off=0;
 	f_desc_table_fat[i].size=record.filelength;
 	f_desc_table_fat[i].flag=mode;
-	// disp_str("flag:");
+	// kprintf("flag:");
 	// deint(f_desc_table_fat[i].flag);
-	// disp_str("index:");
+	// kprintf("index:");
 	// deint(i);
 	p_proc_current->task.filp[fd] ->fd_node.fd_file = &f_desc_table_fat[i];
 	
@@ -552,7 +552,7 @@ STATE IsFile(PCHAR path,PUINT tag)
 
 void init_fs_fat() 
 {
-    disp_str("Initializing fat32 file system...  \n");
+    kprintf("Initializing fat32 file system...  \n");
 	
 	buf = (u8*)K_PHY2LIN(sys_kmalloc(FSBUF_SIZE));
 
@@ -611,9 +611,9 @@ static void mkfs_fat() {
 	driver_msg.PROC_NR	= proc2pid(p_proc_current);
 	hd_ioctl(&driver_msg);
 
-	disp_str("dev size: ");
-	disp_int(geo.size);
-	disp_str(" sectors\n");
+	kprintf("dev size: ");
+	kprintf("%d", geo.size);
+	kprintf(" sectors\n");
 
     TotalSectors = geo.size;
 
@@ -870,7 +870,7 @@ int sys_ListDir(void *uesp) {
 	// 	DirCheckup(array);
 	// }else {
 	// 	DisErrorInfo(state);
-	// 	disp_str("\n");
+	// 	kprintf("\n");
 	// }
 	// DestroyDArray(array);
 	return 0;
@@ -880,31 +880,31 @@ void DisErrorInfo(STATE state)
 {
 	if(state==SYSERROR)
 	{
-		disp_str("          system error\n");
+		kprintf("          system error\n");
 	}
 	else if(state==VDISKERROR)
 	{
-		disp_str("          disk error\n");
+		kprintf("          disk error\n");
 	}
 	else if(state==INSUFFICIENTSPACE)
 	{
-		disp_str("          no much space\n");
+		kprintf("          no much space\n");
 	}
 	else if(state==WRONGPATH)
 	{
-		disp_str("          path error\n");
+		kprintf("          path error\n");
 	}
 	else if(state==NAMEEXIST)
 	{
-		disp_str("          name exists\n");
+		kprintf("          name exists\n");
 	}
 	else if(state==ACCESSDENIED)
 	{
-		disp_str("          deny access\n");
+		kprintf("          deny access\n");
 	}
 	else
 	{
-		disp_str("          unknown error\n");
+		kprintf("          unknown error\n");
 	}
 }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 7687ee6..c1eb777 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -28,7 +28,7 @@ int sys_fork()
 	p_child = alloc_PCB();
 	if( 0==p_child )
 	{
-		disp_color_str("PCB NULL,fork faild!",0x74);
+		vga_write_str_color("PCB NULL,fork faild!",0x74);
 		return -1;
 	}
 	else
@@ -56,9 +56,9 @@ int sys_fork()
 		/****************用户进程数+1****************************/
 		u_proc_sum += 1;
 
-		disp_color_str("[fork success:",0x72);
-		disp_color_str(p_proc_current->task.p_name,0x72);
-		disp_color_str("]",0x72);
+		vga_write_str_color("[fork success:",0x72);
+		vga_write_str_color(p_proc_current->task.p_name,0x72);
+		vga_write_str_color("]",0x72);
 		
 		//anything child need is prepared now, set its state to ready. added by xw, 17/12/11
 		p_child->task.stat = READY;
diff --git a/kernel/global.c b/kernel/global.c
index d5b43ae..b49ab0b 100644
--- a/kernel/global.c
+++ b/kernel/global.c
@@ -24,7 +24,6 @@
 
 int kernel_initial;
 int ticks;
-int disp_pos;
 u8 gdt_ptr[6];
 DESCRIPTOR gdt[GDT_SIZE];
 u8 idt_ptr[6];
diff --git a/kernel/kernel.asm b/kernel/kernel.asm
index 5e079f7..e18a1c8 100644
--- a/kernel/kernel.asm
+++ b/kernel/kernel.asm
@@ -15,11 +15,9 @@ extern	exception_handler
 extern	spurious_irq
 extern	clock_handler
 extern	disp_str
-extern	delay
 extern	irq_table
 extern	page_fault_handler
 extern	divide_error_handler	;added by xw, 18/12/22
-extern	disp_int
 extern  schedule
 extern  switch_pde
 
@@ -28,7 +26,6 @@ extern	gdt_ptr
 extern	idt_ptr
 extern	p_proc_current
 extern	tss
-extern	disp_pos
 extern	k_reenter
 extern	sys_call_table
 extern 	cr3_ready			;add by visual 2016.4.5
@@ -141,7 +138,6 @@ _start:
 	;mov	esp, StackTop	; 堆栈在 bss 段中
 	mov	esp, KernelStackTop	; 堆栈在 bss 段中
 
-	mov	dword [disp_pos], 0
 
 	sgdt	[gdt_ptr]	; cstart() 中将会用到 gdt_ptr
 	call	cstart		; 在此函数中改变了gdt_ptr，让它指向新的GDT
diff --git a/kernel/main.c b/kernel/main.c
index 70f5d1a..b3c821b 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -32,13 +32,13 @@ int kernel_main()
 {
 	int error;
 
-	disp_pos = 0;
+	vga_set_disppos(0);
 	for (int i = 0; i < 25; i++) {
 		for (int j = 0; j < 80; j++) {
 			kprintf(" ");
 		}
 	}
-	disp_pos = 0;
+	vga_set_disppos(0);
 
 	kprintf("-----Kernel Initialization Begins-----\n");
 	kernel_initial = 1;	//kernel is in initial state. added by xw, 18/5/31
@@ -199,7 +199,7 @@ static int initialize_processes()
 		/***************初始化PID进程页表*****************************/
 		if( 0 != init_page_pte(pid) )
 		{
-			disp_color_str("kernel_main Error:init_page_pte",0x74);
+			vga_write_str_color("kernel_main Error:init_page_pte",0x74);
 			return -1;
 		}
 		//	pde_addr_phy_temp = get_pde_phy_addr(pid);//获取该进程页目录物理地址			//delete by visual 2016.5.19
@@ -214,7 +214,7 @@ static int initialize_processes()
 			//addr_phy_temp = (u32)do_kmalloc_4k();//为栈申请一个物理页,Task的栈是在内核里面	//delete by visual 2016.5.19
 			//if( addr_phy_temp<0 || (addr_phy_temp&0x3FF)!=0  )
 			//{
-			//	disp_color_str("kernel_main Error:addr_phy_temp",0x74);
+			//	vga_write_str_color("kernel_main Error:addr_phy_temp",0x74);
 			//	return -1;
 			//}
 			err_temp = lin_mapping_phy(	AddrLin,//线性地址						//add by visual 2016.5.9
@@ -224,7 +224,7 @@ static int initialize_processes()
 										PG_P  | PG_USU | PG_RWW);//页表的属性位
 			if( err_temp!=0 )
 			{
-				disp_color_str("kernel_main Error:lin_mapping_phy",0x74);
+				vga_write_str_color("kernel_main Error:lin_mapping_phy",0x74);
 				return -1;
 			}
 								
@@ -355,7 +355,7 @@ static int initialize_processes()
 		/***************初始化PID进程页表*****************************/
 		if( 0 != init_page_pte(pid) )
 		{
-			disp_color_str("kernel_main Error:init_page_pte",0x74);
+			vga_write_str_color("kernel_main Error:init_page_pte",0x74);
 			return -1;
 		}
 		//pde_addr_phy_temp = get_pde_phy_addr(pid);//获取该进程页目录物理地址	//edit by visual 2016.5.19
@@ -370,7 +370,7 @@ static int initialize_processes()
 			//addr_phy_temp = (u32)do_kmalloc_4k();//为栈申请一个物理页,Task的栈是在内核里面 //delete by visual 2016.5.19
 			//if( addr_phy_temp<0 || (addr_phy_temp&0x3FF)!=0  )
 			//{
-			//	disp_color_str("kernel_main Error:addr_phy_temp",0x74);
+			//	vga_write_str_color("kernel_main Error:addr_phy_temp",0x74);
 			//	return -1;
 			//}
 			err_temp = lin_mapping_phy(	AddrLin,//线性地址
@@ -380,7 +380,7 @@ static int initialize_processes()
 										PG_P  | PG_USU | PG_RWW);//页表的属性位
 			if( err_temp!=0 )
 			{
-				disp_color_str("kernel_main Error:lin_mapping_phy",0x74);
+				vga_write_str_color("kernel_main Error:lin_mapping_phy",0x74);
 				return -1;
 			}
 								
diff --git a/kernel/memman.c b/kernel/memman.c
index b84c167..ec5c507 100644
--- a/kernel/memman.c
+++ b/kernel/memman.c
@@ -340,22 +340,22 @@ void memman_test()
 	
 	p1 = (u32 *)do_malloc(4);
 	if(-1 != (u32)p1){	//打印p1，当前空闲内存信息，p1所指内存的内容
-		disp_str("START");
-		disp_int((u32)p1);
+		kprintf("START");
+		kprintf("%d", (u32)p1);
 		//disp_free();
 		*p1 = TEST;
-		disp_int(*p1);
-		disp_str("END");
+		kprintf("%d", *p1);
+		kprintf("END");
 	}
 	
 	p2 = (u32 *)do_kmalloc(4);
 	if(-1 != (u32)p2){
-		disp_str("START");
-		disp_int((u32)p2);
+		kprintf("START");
+		kprintf("%d", (u32)p2);
 		//disp_free();
 		*p2 = TEST;
-		disp_int(*p2);
-		disp_str("END");
+		kprintf("%d", *p2);
+		kprintf("END");
 	}
 	
 	do_free((u32)p1,4);
@@ -363,42 +363,42 @@ void memman_test()
 	
 	p3 = (u32 *)do_malloc_4k();
 	if(-1 != (u32)p3){	
-		disp_str("START");
-		disp_int((u32)p3);
+		kprintf("START");
+		kprintf("%d", (u32)p3);
 		//disp_free();
 		*p3 = TEST;
-		disp_int(*p3);
+		kprintf("%d", *p3);
 		p = p3 + 2044;
 		*p = 0x22334455;
-		disp_int(*p);
+		kprintf("%d", *p);
 		p += 2048;
 		*p = 0x33445566;
-		disp_int(*p);
-		disp_str("END");
+		kprintf("%d", *p);
+		kprintf("END");
 	}
 	
 	p4 = (u32 *)do_kmalloc_4k(4);
 	if(-1 != (u32)p4){
-		disp_str("START");
-		disp_int((u32)p4);
+		kprintf("START");
+		kprintf("%d", (u32)p4);
 		//disp_free();
 		*p4 = TEST;
-		disp_int(*p4);
+		kprintf("%d", *p4);
 		p = p4 + 2044;
 		*p = 0x22334455;
-		disp_int(*p);
+		kprintf("%d", *p);
 		p += 2048;
 		*p = 0x33445566;
-		disp_int(*p);
-		disp_str("END");
+		kprintf("%d", *p);
+		kprintf("END");
 	}
 	
 	do_free_4k((u32)p3);
 	do_free_4k((u32)p4);
 	
-	disp_str("START");
+	kprintf("START");
 	disp_free();
-	disp_str("END");
+	kprintf("END");
 	
 	return;
 }
diff --git a/kernel/pagetbl.c b/kernel/pagetbl.c
index 2b9d840..e2ccc5e 100644
--- a/kernel/pagetbl.c
+++ b/kernel/pagetbl.c
@@ -10,6 +10,7 @@
 #include "global.h"
 #include "proto.h"
 #include "memman.h"
+#include "stdio.h"
 
 // to determine if a page fault is reparable. added by xw, 18/6/11
 u32 cr2_save;
@@ -38,7 +39,7 @@ u32 init_page_pte(u32 pid)
 
 	if (pde_addr_phy_temp < 0 || (pde_addr_phy_temp & 0x3FF) != 0) // add by visual 2016.5.9
 	{
-		disp_color_str("init_page_pte Error:pde_addr_phy_temp", 0x74);
+		vga_write_str_color("init_page_pte Error:pde_addr_phy_temp", 0x74);
 		return -1;
 	}
 
@@ -55,7 +56,7 @@ u32 init_page_pte(u32 pid)
 					   PG_P | PG_USS | PG_RWW); //页表的属性位（系统权限）				//edit by visual 2016.5.17
 		if (err_temp != 0)
 		{
-			disp_color_str("init_page_pte Error:lin_mapping_phy", 0x74);
+			vga_write_str_color("init_page_pte Error:lin_mapping_phy", 0x74);
 			return -1;
 		}
 	}
@@ -81,18 +82,18 @@ void page_fault_handler(u32 vec_no,   //异常编号，此时应该是14，代
 	// if page fault happens in kernel, it's an error.
 	if (kernel_initial == 1)
 	{
-		disp_str("\n");
-		disp_color_str("Page Fault\n", 0x74);
-		disp_color_str("eip=", 0x74); //灰底红字
-		disp_int(eip);
-		disp_color_str("eflags=", 0x74);
-		disp_int(eflags);
-		disp_color_str("cs=", 0x74);
-		disp_int(cs);
-		disp_color_str("err_code=", 0x74);
-		disp_int(err_code);
-		disp_color_str("Cr2=", 0x74); //灰底红字
-		disp_int(cr2);
+		kprintf("\n");
+		vga_write_str_color("Page Fault\n", 0x74);
+		vga_write_str_color("eip=", 0x74); //灰底红字
+		kprintf("%d", eip);
+		vga_write_str_color("eflags=", 0x74);
+		kprintf("%d", eflags);
+		vga_write_str_color("cs=", 0x74);
+		kprintf("%d", cs);
+		vga_write_str_color("err_code=", 0x74);
+		kprintf("%d", err_code);
+		vga_write_str_color("Cr2=", 0x74); //灰底红字
+		kprintf("%d", cr2);
 		halt();
 	}
 
@@ -106,26 +107,26 @@ void page_fault_handler(u32 vec_no,   //异常编号，此时应该是14，代
 		cr2_count++;
 		if (cr2_count == 5)
 		{
-			disp_str("\n");
-			disp_color_str("Page Fault\n", 0x74);
-			disp_color_str("eip=", 0x74); //灰底红字
-			disp_int(eip);
-			disp_color_str("eflags=", 0x74);
-			disp_int(eflags);
-			disp_color_str("cs=", 0x74);
-			disp_int(cs);
-			disp_color_str("err_code=", 0x74);
-			disp_int(err_code);
-			disp_color_str("Cr2=", 0x74); //灰底红字
-			disp_int(cr2);
-			disp_color_str("Cr3=", 0x74);
-			disp_int(p_proc_current->task.cr3);
+			kprintf("\n");
+			vga_write_str_color("Page Fault\n", 0x74);
+			vga_write_str_color("eip=", 0x74); //灰底红字
+			kprintf("%d", eip);
+			vga_write_str_color("eflags=", 0x74);
+			kprintf("%d", eflags);
+			vga_write_str_color("cs=", 0x74);
+			kprintf("%d", cs);
+			vga_write_str_color("err_code=", 0x74);
+			kprintf("%d", err_code);
+			vga_write_str_color("Cr2=", 0x74); //灰底红字
+			kprintf("%d", cr2);
+			vga_write_str_color("Cr3=", 0x74);
+			kprintf("%d", p_proc_current->task.cr3);
 			//获取页目录中填写的内容
-			disp_color_str("Pde=", 0x74);
-			disp_int(*((u32 *)K_PHY2LIN(pde_addr_phy_temp) + get_pde_index(cr2)));
+			vga_write_str_color("Pde=", 0x74);
+			kprintf("%d", *((u32 *)K_PHY2LIN(pde_addr_phy_temp) + get_pde_index(cr2)));
 			//获取页表中填写的内容
-			disp_color_str("Pte=", 0x74);
-			disp_int(*((u32 *)K_PHY2LIN(pte_addr_phy_temp) + get_pte_index(cr2)));
+			vga_write_str_color("Pte=", 0x74);
+			kprintf("%d", *((u32 *)K_PHY2LIN(pte_addr_phy_temp) + get_pte_index(cr2)));
 			halt();
 		}
 	}
@@ -137,15 +138,15 @@ void page_fault_handler(u32 vec_no,   //异常编号，此时应该是14，代
 
 	if (0 == pte_exist(pde_addr_phy_temp, cr2))
 	{ //页表不存在
-		// disp_color_str("[Pde Fault!]",0x74);	//灰底红字
+		// vga_write_str_color("[Pde Fault!]",0x74);	//灰底红字
 		(*((u32 *)K_PHY2LIN(pde_addr_phy_temp) + get_pde_index(cr2))) |= PG_P;
-		// disp_color_str("[Solved]",0x74);
+		// vga_write_str_color("[Solved]",0x74);
 	}
 	else
 	{ //只是缺少物理页
-		// disp_color_str("[Pte Fault!]",0x74);	//灰底红字
+		// vga_write_str_color("[Pte Fault!]",0x74);	//灰底红字
 		(*((u32 *)K_PHY2LIN(pte_addr_phy_temp) + get_pte_index(cr2))) |= PG_P;
-		// disp_color_str("[Solved]",0x74);
+		// vga_write_str_color("[Solved]",0x74);
 	}
 	refresh_page_cache();
 }
@@ -309,7 +310,7 @@ int lin_mapping_phy(u32 AddrLin,	      //线性地址
 
 		if (pte_addr_phy < 0 || (pte_addr_phy & 0x3FF) != 0) // add by visual 2016.5.9
 		{
-			disp_color_str("lin_mapping_phy Error:pte_addr_phy", 0x74);
+			vga_write_str_color("lin_mapping_phy Error:pte_addr_phy", 0x74);
 			return -1;
 		}
 
@@ -332,7 +333,7 @@ int lin_mapping_phy(u32 AddrLin,	      //线性地址
 				phy_addr = do_kmalloc_4k(); //从内核物理地址申请一页
 			else
 			{
-				// disp_str("%");
+				// kprintf("%");
 				phy_addr = do_malloc_4k(); //从用户物理地址空间申请一页
 			}
 		}
@@ -349,7 +350,7 @@ int lin_mapping_phy(u32 AddrLin,	      //线性地址
 
 	if (phy_addr < 0 || (phy_addr & 0x3FF) != 0)
 	{
-		disp_color_str("lin_mapping_phy:phy_addr ERROR", 0x74);
+		vga_write_str_color("lin_mapping_phy:phy_addr ERROR", 0x74);
 		return -1;
 	}
 
diff --git a/kernel/protect.c b/kernel/protect.c
index 85cab81..28f3d20 100644
--- a/kernel/protect.c
+++ b/kernel/protect.c
@@ -12,6 +12,7 @@
 #include "global.h"
 #include "proto.h"
 #include "string.h"
+#include "stdio.h"
 
 
 /* 本文件内函数声明 */
@@ -270,29 +271,30 @@ static void init_descriptor(DESCRIPTOR * p_desc, u32 base, u32 limit, u16 attrib
 				};
 
 	/* 通过打印空格的方式清空屏幕的前五行，并把 disp_pos 清零 */
-	disp_pos = 0;
+	vga_set_disppos(0);
 	for(i=0;i<80*5;i++){
-		disp_str(" ");
+		kprintf(" ");
 	}
-	disp_pos = 0;
+	vga_set_disppos(0);
 
-	disp_color_str("Exception! --> ", text_color);
-	disp_color_str(err_description[vec_no], text_color);
-	disp_color_str("\n\n", text_color);
-	disp_color_str("EFLAGS:", text_color);
-	disp_int(eflags);
-	disp_color_str("CS:", text_color);
-	disp_int(cs);
-	disp_color_str("EIP:", text_color);
-	disp_int(eip);
+
+	vga_write_str_color("Exception! --> ", text_color);
+	vga_write_str_color(err_description[vec_no], text_color);
+	vga_write_str_color("\n\n", text_color);
+	vga_write_str_color("EFLAGS:", text_color);
+	kprintf("%d", eflags);
+	vga_write_str_color("CS:", text_color);
+	kprintf("%d", cs);
+	vga_write_str_color("EIP:", text_color);
+	kprintf("%d", eip);
 
 	if(err_code != 0xFFFFFFFF){
-		disp_color_str("Error code:", text_color);
-		disp_int(err_code);
+		vga_write_str_color("Error code:", text_color);
+		kprintf("%d", err_code);
 	}
 	
 	//added by xw, 18/12/19
-	disp_str("\n");
+	kprintf("\n");
 
 	//added by xw, 18/12/19
 	p_proc_current->task.stat = KILLED;
@@ -320,7 +322,7 @@ static void init_descriptor(DESCRIPTOR * p_desc, u32 base, u32 limit, u16 attrib
 	
 	while (1)
 	{
-		disp_str("Loop in divide error handler...\n");
+		kprintf("Loop in divide error handler...\n");
 
 		i = 100;
 		while(--i){
diff --git a/kernel/pthread.c b/kernel/pthread.c
index 04a9cc7..b942573 100644
--- a/kernel/pthread.c
+++ b/kernel/pthread.c
@@ -27,16 +27,16 @@ int sys_pthread(void *entry)
 	
 	/*if(p_proc_current->task.info.type == TYPE_THREAD )
 	{//线程不能创建线程
-		disp_color_str("[pthread failed:",0x74);
-		disp_color_str(p_proc_current->task.p_name,0x74);
-		disp_color_str("]",0x74);
+		vga_write_str_color("[pthread failed:",0x74);
+		vga_write_str_color(p_proc_current->task.p_name,0x74);
+		vga_write_str_color("]",0x74);
 		return -1;
 	}*/
 	/*****************申请空白PCB表**********************/
 	p_child = alloc_PCB();
 	if( 0==p_child )
 	{
-		disp_color_str("PCB NULL,pthread faild!",0x74);
+		vga_write_str_color("PCB NULL,pthread faild!",0x74);
 		return -1;
 	}
 	else
@@ -78,9 +78,9 @@ int sys_pthread(void *entry)
 		/****************用户进程数+1****************************/
 		u_proc_sum += 1;
 		
-		disp_color_str("[pthread success:",0x72);
-		disp_color_str(p_proc_current->task.p_name,0x72);
-		disp_color_str("]",0x72);
+		vga_write_str_color("[pthread success:",0x72);
+		vga_write_str_color(p_proc_current->task.p_name,0x72);
+		vga_write_str_color("]",0x72);
 		
 		//anything child need is prepared now, set its state to ready. added by xw, 17/12/11
 		p_child->task.stat = READY;	
diff --git a/kernel/start.c b/kernel/start.c
index 9d8fe19..9c44511 100644
--- a/kernel/start.c
+++ b/kernel/start.c
@@ -57,6 +57,7 @@ _warn(const char *file, int line, const char *fmt,...)
  *======================================================================*/
 void cstart()
 {
+	vga_set_disppos(0);
 	kprintf("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n-----\"cstart\" begins-----\n");
 
 	// 将 LOADER 中的 GDT 复制到新的 GDT 中
diff --git a/kernel/syscallc.c b/kernel/syscallc.c
index cb4d2b3..2a2170e 100644
--- a/kernel/syscallc.c
+++ b/kernel/syscallc.c
@@ -13,6 +13,7 @@
 #include "global.h"
 #include "proto.h"
 #include "memman.h"
+#include "stdio.h"
 
 struct memfree *memarg = 0;
 
@@ -121,7 +122,7 @@ int sys_free_4k(void* AddrLin)
  *======================================================================*/
 void sys_udisp_int(int arg)
 {
-	disp_int(arg);
+	kprintf("%d", arg);
 	return ;
 }
 
@@ -131,6 +132,6 @@ void sys_udisp_int(int arg)
  *======================================================================*/
 void sys_udisp_str(char *arg)
 {
-	disp_str(arg);
+	kprintf(arg);
 	return ;
 }
\ No newline at end of file
diff --git a/kernel/testfunc.c b/kernel/testfunc.c
index bfe3c84..bbde009 100644
--- a/kernel/testfunc.c
+++ b/kernel/testfunc.c
@@ -11,6 +11,7 @@
 #include "proc.h"
 #include "global.h"
 #include "proto.h"
+#include "stdio.h"
 
 /* 
  * This syscall needs long time to finish, so we can use it 
@@ -21,7 +22,7 @@ void sys_print_E()
 {		
 	int i, j;
 	
-	disp_str("E( ");
+	kprintf("E( ");
 	
 	i = 100;
 	while(--i){
@@ -29,7 +30,7 @@ void sys_print_E()
 		while(--j){}
 	}
 	
-	disp_str(") ");
+	kprintf(") ");
 }
 
 /* 
@@ -41,7 +42,7 @@ void sys_print_F()
 {
 	int i, j;
 	
-	disp_str("F( ");
+	kprintf("F( ");
 	
 	i = 100;
 	while(--i){
@@ -49,5 +50,5 @@ void sys_print_F()
 		while(--j){}
 	}
 	
-	disp_str(") ");
+	kprintf(") ");
 }
diff --git a/kernel/tty.c b/kernel/tty.c
index 3f21ada..84177bf 100644
--- a/kernel/tty.c
+++ b/kernel/tty.c
@@ -99,9 +99,9 @@ void task_tty()
 	//设置第一个tty光标位置，第一个tty需要特殊处理
 	disable_int();
 	outb(CRTC_ADDR_REG, CURSOR_H);
-	outb(CRTC_DATA_REG, ((disp_pos / 2) >> 8) & 0xFF);
+	outb(CRTC_DATA_REG, ((vga_get_disppos()) >> 8) & 0xFF);
 	outb(CRTC_ADDR_REG, CURSOR_L);
-	outb(CRTC_DATA_REG, (disp_pos / 2) & 0xFF);
+	outb(CRTC_DATA_REG, (vga_get_disppos()) & 0xFF);
 	enable_int();
 
 	//轮询
diff --git a/kernel/uart.c b/kernel/uart.c
new file mode 100644
index 0000000..b438d40
--- /dev/null
+++ b/kernel/uart.c
@@ -0,0 +1,54 @@
+#include "uart.h"
+#include "x86.h"
+#include "tty.h"
+#include "const.h"
+#include "type.h"
+#include "assert.h"
+#include "stdio.h"
+#include "memman.h"
+
+
+void put_irq_handler(int irq, irq_handler handler);
+void enable_irq(int irq);
+
+int init_serial() {
+   outb(PORT + 1, 0x00);    // Disable all interrupts
+   outb(PORT + 3, 0x80);    // Enable DLAB (set baud rate divisor)
+   outb(PORT + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
+   outb(PORT + 1, 0x00);    //                  (hi byte)
+   outb(PORT + 3, 0x03);    // 8 bits, no parity, one stop bit
+   outb(PORT + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
+   outb(PORT + 4, 0x0B);    // IRQs enabled, RTS/DSR set
+   outb(PORT + 4, 0x1E);    // Set in loopback mode, test the serial chip
+   outb(PORT + 0, 0xAE);    // Test serial chip (send byte 0xAE and check if serial returns same byte)
+ 
+   // Check if serial is faulty (i.e: not same byte as sent)
+   if(inb(PORT + 0) != 0xAE) {
+      assert(0);
+      return 1;
+   }
+ 
+   // If serial is not faulty set it in normal operation mode
+   // (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
+   outb(PORT + 4, 0x0f);
+   return 0;
+}
+static inline int is_transmit_empty() {
+   return inb(PORT + 5) & 0x20;
+}
+
+static inline int serial_received() {
+   return inb(PORT + 5) & 1;
+}
+ 
+char read_serial() {
+   while (serial_received() == 0);
+ 
+   return inb(PORT);
+}
+
+void write_serial(char a) {
+   while (is_transmit_empty() == 0);
+ 
+   outb(PORT,a);
+}
\ No newline at end of file
diff --git a/lib/Makefrag b/lib/Makefrag
index 27b511d..e43dc83 100644
--- a/lib/Makefrag
+++ b/lib/Makefrag
@@ -6,6 +6,7 @@ LIB_OBJS :=	lib/string.o		\
 		lib/kprintf.o		\
 		lib/scanf.o		\
 		lib/printfmt.o		\
+		lib/vga_display.o		\
 
 LIB_OBJS := $(patsubst %, $(OBJDIR)/%, $(LIB_OBJS))
 
diff --git a/lib/klib.c b/lib/klib.c
deleted file mode 100644
index 7c443e3..0000000
--- a/lib/klib.c
+++ /dev/null
@@ -1,75 +0,0 @@
-
-/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-                            klib.c
-++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-                                                    Forrest Yu, 2005
-++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
-
-#include "type.h"
-#include "const.h"
-#include "protect.h"
-#include "string.h"
-#include "proc.h"
-#include "global.h"
-#include "proto.h"
-
-
-/*======================================================================*
-                               itoa
- *======================================================================*/
- char * itoa(char * str, int num)/* 数字前面的 0 不被显示出来, 比如 0000B800 被显示成 B800 */
-{
-	char *	p = str;
-	char	ch;
-	int	i;
-	int	flag = FALSE;
-
-	*p++ = '0';
-	*p++ = 'x';
-
-	if(num == 0){
-		*p++ = '0';
-	}
-	else{	
-		for(i=28;i>=0;i-=4){
-			ch = (num >> i) & 0xF;
-			if(flag || (ch > 0)){
-				flag = TRUE;
-				ch += '0';
-				if(ch > '9'){
-					ch += 7;
-				}
-				*p++ = ch;
-			}
-		}
-	}
-
-	*p = 0;
-
-	return str;
-}
-
-
-/*======================================================================*
-                               disp_int
- *======================================================================*/
- void disp_int(int input)
-{
-	char output[16];
-	itoa(output, input);
-	disp_str(output);
-}
-
-/*======================================================================*
-                               delay
- *======================================================================*/
- void delay(int time)
-{
-	int i, j, k;
-	for(k=0;k<time;k++){
-		/*for(i=0;i<10000;i++){	for Virtual PC	*/
-		for(i=0;i<10;i++){/*	for Bochs	*/
-			for(j=0;j<10000;j++){}
-		}
-	}
-}
diff --git a/lib/kliba.asm b/lib/kliba.asm
deleted file mode 100644
index 528cd7e..0000000
--- a/lib/kliba.asm
+++ /dev/null
@@ -1,124 +0,0 @@
-
-; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-;                              klib.asm
-; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-;                                                       Forrest Yu, 2005
-; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-
-%include "sconst.inc"
-
-; 导入全局变量
-extern	disp_pos
-
-
-[SECTION .text]
-
-; 导出函数
-global	disp_str
-global	disp_color_str
-global  write_char	; added by mingxuan 2019-5-19
-
-; ========================================================================
-;                  void disp_str(char * info);
-; ========================================================================
-disp_str:
-	push	ebp
-	mov	ebp, esp
-	pushad
-
-	mov	esi, [ebp + 8]	; pszInfo
-	mov	edi, [disp_pos]
-	mov	ah, 0Fh
-.1:
-	lodsb
-	test	al, al
-	jz	.2
-	cmp	al, 0Ah	; 是回车吗?
-	jnz	.3
-	push	eax
-	mov	eax, edi
-	mov	bl, 160
-	div	bl
-	and	eax, 0FFh
-	inc	eax
-	mov	bl, 160
-	mul	bl
-	mov	edi, eax
-	pop	eax
-	jmp	.1
-.3:
-;added by xw, 17/12/11
-;added begin
-	cmp edi, 1F40h
-	jnz .4
-	mov edi, 0FA0h
-.4:
-;added end
-	mov	[gs:edi], ax
-	add	edi, 2
-	jmp	.1
-
-.2:
-	mov	[disp_pos], edi
-
-	popad
-	pop	ebp
-	ret
-
-; ========================================================================
-;                  void disp_color_str(char * info, int color);
-; ========================================================================
-disp_color_str:
-	push	ebp
-	mov	ebp, esp
-	pushad
-
-	mov	esi, [ebp + 8]	; pszInfo
-	mov	edi, [disp_pos]
-	mov	ah, [ebp + 12]	; color
-.1:
-	lodsb
-	test	al, al
-	jz	.2
-	cmp	al, 0Ah	; 是回车吗?
-	jnz	.3
-	push	eax
-	mov	eax, edi
-	mov	bl, 160
-	div	bl
-	and	eax, 0FFh
-	inc	eax
-	mov	bl, 160
-	mul	bl
-	mov	edi, eax
-	pop	eax
-	jmp	.1
-.3:
-	mov	[gs:edi], ax
-	add	edi, 2
-	jmp	.1
-
-.2:
-	mov	[disp_pos], edi
-
-	popad
-	pop	ebp
-	ret
-
-; ========================================================================
-;		   void write_char(char ch);
-; ========================================================================
-write_char:
-	push 	ebp
-	mov ebp,esp
-	
-	mov esi,[ebp+8] 
-	mov edi,[disp_pos]
-	
-	push eax
-	mov eax,esi
-	mov	ah, 0Fh
-	mov	[gs:edi], ax
-	pop eax
-	pop ebp
-	ret
\ No newline at end of file
diff --git a/lib/kprintf.c b/lib/kprintf.c
index 66669ec..af15ab0 100644
--- a/lib/kprintf.c
+++ b/lib/kprintf.c
@@ -3,12 +3,12 @@
 #include "proc.h"
 #include "global.h"
 #include "proto.h"
+#include "uart.h"
 
 static void 
 kprintfputch(int ch, void *b)
 {
-	char buf[2]={(char)ch,'\0'};
-	disp_str(buf);
+	vga_write_char(ch, WHITE_CHAR);
 }
 
 int
@@ -30,5 +30,30 @@ kprintf(const char *fmt, ...)
 	rc = vkprintf(fmt, ap);
 	va_end(ap);
 
+	return rc;
+}
+
+static void
+uart_putch(int ch, void *b) {
+	write_serial(ch);
+}
+
+
+int
+v_uart_kprintf(const char *fmt, va_list ap)
+{
+	vprintfmt((void*)uart_putch, NULL, fmt, ap);
+	return 0;
+}
+
+int uart_kprintf(const char *fmt, ...)
+{
+	va_list ap;
+	int rc;
+
+	va_start(ap, fmt);
+	rc = v_uart_kprintf(fmt, ap);
+	va_end(ap);
+
 	return rc;
 }
\ No newline at end of file
diff --git a/lib/vga_display.c b/lib/vga_display.c
new file mode 100644
index 0000000..61ab6d6
--- /dev/null
+++ b/lib/vga_display.c
@@ -0,0 +1,100 @@
+#include "tty.h"
+#include "x86.h"
+#include "console.h"
+#include "const.h"
+#include "assert.h"
+
+/*****************************************************************************
+    Set the position of cursor in the screen
+    @param position the position in the linear array of video buffer
+*/
+static inline void vga_set_cursor(unsigned int position)
+{
+	disable_int();
+	outb(CRTC_ADDR_REG, CURSOR_H);
+	outb(CRTC_DATA_REG, (position >> 8) & 0xFF);
+	outb(CRTC_ADDR_REG, CURSOR_L);
+	outb(CRTC_DATA_REG, position & 0xFF);
+	enable_int();
+}
+
+/*****************************************************************************
+    Disable the blinking cursor
+*/
+static inline void vga_disable_cursor()
+{
+	outb(CRTC_ADDR_REG, 0x0A);
+	outb(CRTC_DATA_REG, 0x20);
+}
+
+/*****************************************************************************
+    Enable the blinking cursor, and set the height of the cursor
+    The cursor is splited into 16 units
+    @param cursor_start the start unit index
+    @param cursor_end  the ending unit index
+*/
+static inline void vga_enable_cursor(u8 cursor_start, u8 cursor_end)
+{
+	outb(0x3D4, 0x0A);
+	outb(0x3D5, (inb(0x3D5) & 0xC0) | cursor_start);
+
+	outb(0x3D4, 0x0B);
+	outb(0x3D5, (inb(0x3D5) & 0xE0) | cursor_end);
+}
+
+/*****************************************************************************
+    Write data directly to Video Memory cell
+    @param pos  text mode position(pos*2 yourself)
+    @param dat  data to be written, with format [ BG | FG |  ASCII  ]
+*/
+static inline void vga_put_raw(u32 pos, u16 dat)
+{
+	u16 *pch = (u16 *)K_PHY2LIN(V_MEM_BASE + pos);
+	*pch = dat;
+}
+
+static inline void vga_flush_blankline(int line_no)
+{
+	u32 *dst = (u32 *)K_PHY2LIN(V_MEM_BASE + line_no * SCR_WIDTH * 2);
+	for (int i = 0; i < SCR_WIDTH * sizeof(u16) / sizeof(u32); ++i)
+	{
+		*dst++ = (BLANK << 16) | BLANK;
+	}
+}
+
+static int disp_pos = 0;
+
+void vga_set_disppos(int new_pos) {
+    disp_pos = new_pos;
+}
+int vga_get_disppos() {
+    return disp_pos;
+}
+
+/**********************************************************
+ * Write char to disp_pos and then increase disp_pos
+ * @param ch the character
+ * @param color the color, in 8-bit format
+*/
+void vga_write_char(const char ch, u16 color) {
+    if (ch == '\n') {
+        disp_pos = (disp_pos / SCR_WIDTH + 1) * SCR_WIDTH;
+    }
+    else {
+        vga_put_raw(disp_pos * 2, (color << 8) | (u16)ch);
+        disp_pos ++;
+    }
+    vga_set_cursor(disp_pos);
+}
+
+void vga_write_str(const char * str) {
+    for (char* s = (char *)str; *s; ++s) {
+        vga_write_char(*s, WHITE_CHAR);
+    }
+}
+
+void vga_write_str_color(const char * str, u8 color) {
+    for (char* s = (char *)str; *s; ++s) {
+        vga_write_char(*s, color);
+    }
+}
\ No newline at end of file