diff --git a/boot/Makefile b/boot/Makefile
index fc930db..9c506df 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -5,7 +5,7 @@ PROG = boot
 SRCS = srt0.S gdt.S boot.c
 OBJS = srt0.o gdt.o boot.o
 
-ESRCS = pccon.c sricon.c print.c a20.c time.c mem.c
+ESRCS = pccon.c sricon.c print.c fmt.c a20.c time.c mem.c
 OBJS += $(ESRCS:.c=.o)
 
 include $(SDIR)/Makefile.inc
diff --git a/boot/dat.h b/boot/dat.h
index d71c07e..dedfe79 100644
--- a/boot/dat.h
+++ b/boot/dat.h
@@ -2,6 +2,7 @@
 // 0x60	Read/Write	Data Port
 // 0x64	Read	Status Register
 // 0x64	Write	Command Register
+#define TABWIDTH 8
 
 enum{
 	CON_PC,
@@ -42,6 +43,16 @@ typedef struct{
 	u32 type;		/* Type of block */
 } __attribute__((packed)) BIOSmmap;
 
+// fmt.c
+typedef struct{
+	int ucase;
+	int padch;
+	char *p;
+	char *ep;
+	int f1, f2, f3;
+	va_list ap;
+}Op;
+
 // gdt.S
 extern volatile struct BIOSreg BIOSreg;
 
diff --git a/boot/fmt.c b/boot/fmt.c
new file mode 100644
index 0000000..6d1ca01
--- /dev/null
+++ b/boot/fmt.c
@@ -0,0 +1,304 @@
+#include <u.h>
+#include "dat.h"
+#include "fn.h"
+
+#define MAXCON 30
+#define IDIGIT 30
+
+enum{
+	FLONG = (1<<0),
+	FSHORT = (1<<2),
+	FUNSIGN = (1<<3),
+};
+
+static Op put(Op, int);
+static Op noconv(Op);
+static Op cconv(Op);
+static Op dconv(Op);
+static Op hconv(Op);
+static Op lconv(Op);
+static Op sconv(Op);
+static Op uconv(Op);
+static Op xconv(Op);
+static Op Xconv(Op);
+static Op percent(Op);
+
+static Op (*fmtconv[MAXCON])(Op) = {
+	noconv,
+	cconv, dconv, hconv, lconv,
+	sconv, uconv, xconv, Xconv,
+	percent,
+};
+
+int fmtindex[128] = {
+	['c'] = 1,
+	['d'] = 2,
+	['h'] = 3,
+	['l'] = 4,
+	['s'] = 5,
+	['u'] = 6,
+	['x'] = 7,
+	['X'] = 8,
+	['%'] = 9,
+};
+int convcnt = 11;
+
+int
+strlen(char *s)
+{
+	char *p = s;
+
+	while(*p)
+		++p;
+	return p-s;
+}
+
+int
+fmtinstall(int c, Op (*f)(Op))
+{
+	c &= 0177;
+	if(fmtindex[c] == 0){
+		if(convcnt + 1 >= MAXCON)
+			return -1;
+		fmtindex[c] = convcnt++;
+	}
+	fmtconv[fmtindex[c]] = f;
+	return 0;
+}
+
+char*
+doprint(char *p, char *ep, char *fmt, va_list ap)
+{
+	int sf1, c;
+	Op o = { .p = p, .ep = ep, .ap = ap };
+
+	while(1){
+		c = *fmt++;
+		if(c != '%'){
+			if(c == 0){
+				if(o.p < o.ep)
+					*o.p = 0;
+				return o.p;
+			}
+			o = put(o, c);
+			continue;
+		}
+		o.f2 = -1;
+		o.f1 = o.f3 = 0;
+		o.padch = sf1 = 0;
+		c = *fmt++;
+		if(c == '-'){
+			sf1 = 1;
+			c = *fmt++;
+		}else if(c == '0' || c == ' '){
+			o.padch = c;
+			c = *fmt++;
+		}
+		while(c >= '0' && c <= '9'){
+			o.f1 = o.f1*10 + c-'0';
+			c = *fmt++;
+		}
+		if(sf1)
+			o.f1 = -o.f1;
+		if(c != '.')
+			goto conv;
+		c = *fmt++;
+		while(c >= '0' && c <= '9'){
+			if(o.f2 < 0)
+				o.f2 = 0;
+			o.f2 = o.f2*10 + c-'0';
+			c = *fmt++;
+		}
+conv:
+		if(c == 0)
+			fmt -= 1;
+		o = (*fmtconv[fmtindex[c&0177]])(o);
+		if(o.f3){
+			c = *fmt++;
+			goto conv;
+		}
+	}
+}
+
+static Op 
+strconv(char *o, Op op, int f1, int f2)
+{
+	int n, c;
+	char *p;
+
+	n = strlen(o);
+	if(f1 >= 0)
+		while(n < f1){
+			op = put(op, op.padch);
+			n += 1;
+		}
+	for(p=o; (c = *p++);)
+		if(f2){
+			op = put(op, c);
+			f2 -= 1;
+		}
+	if(f1 < 0){
+		f1 = -f1;
+		while(n < f1){
+			op = put(op, ' ');
+			n += 1;
+		}	
+	}
+	return op;
+}
+
+static Op 
+numconv(Op op, int base)
+{
+	char b[IDIGIT];
+	int i,f,n;
+	long v;
+	short h;
+
+	i = IDIGIT-1;
+	f = 0;
+	b[i] = 0;
+	switch(op.f3 & (FLONG|FSHORT|FUNSIGN)){
+	case FLONG:
+		v = va_arg(op.ap, long);
+		break;
+	case FUNSIGN|FLONG:
+		v = va_arg(op.ap, ulong);
+		break;
+	case FSHORT:
+		v = h = va_arg(op.ap, short);
+		break;
+	case FUNSIGN|FSHORT:
+		h = va_arg(op.ap, ushort);
+		v = (ushort)h;
+		break;
+	case FUNSIGN:
+		v = va_arg(op.ap, unsigned);
+		break;
+	default:
+		v = va_arg(op.ap, long);
+		break;
+	}
+	if((op.f3 & FUNSIGN) && v < 0){
+		v = -v;
+		f = 1;
+	}
+	while(--i){
+		n = v % base;
+		n += '0';
+		if(n > '9'){
+			n += 'a' - ('9'+1);
+			if(op.ucase)
+				n += 'A'-'a';
+		}
+		b[i] = n;
+		v = (ulong)v / base;
+		if(i < 2)
+			break;
+		if(op.f2 >= 0 && i >= IDIGIT - op.f2)
+			continue;
+		if(v <= 0)
+			break;
+	}
+	if(f)
+		b[--i] = '-';
+	op.f3 = 0;
+	return strconv(b+i, op, op.f1, -1);
+}
+
+static Op
+noconv(Op op)
+{
+	return strconv("***ERROR: noconv***", op, 0, -1);
+}
+
+static Op
+cconv(Op op)
+{
+	char b[2];
+
+	b[0] = va_arg(op.ap, char);
+	b[1] = 0;
+	return strconv(b, op, op.f1, -1);
+}
+
+static Op
+dconv(Op op)
+{
+	return numconv(op, 10);
+}
+
+static Op
+hconv(Op op)
+{
+	op.f3 |= FSHORT;
+	return op;
+}
+
+static Op
+lconv(Op op)
+{
+	op.f3 |= FLONG;
+	return op;
+}
+
+static Op
+uconv(Op op)
+{
+	op.f3 |= FUNSIGN;
+	return op;
+}
+
+static Op
+sconv(Op op)
+{
+	char *p;
+
+	p = va_arg(op.ap, char*);
+	return strconv(p?p:"<nil>", op, op.f1, op.f2);
+}
+
+static Op
+xconv(Op op)
+{
+	return numconv(op, 16);
+}
+
+static Op
+Xconv(Op op)
+{
+	op.ucase = 1;
+	op = numconv(op, 16);
+	op.ucase = 0;
+	return op;
+}
+
+static Op
+percent(Op op)
+{
+	return put(op, '%');
+}
+
+static Op
+put(Op o, int c)
+{
+	static int pos;
+	int opos;
+
+	if(c == 0)
+		return o;
+	if(c == '\t'){
+		opos = pos;
+		pos = (opos+TABWIDTH) & (~(TABWIDTH-1));
+		while(opos++ < pos && o.p < o.ep)
+			*o.p++ = ' ';
+		return o;
+	}	
+	if(o.p < o.ep){
+		*o.p++ = c;
+		pos++;
+	}
+	if(c == '\n')
+		pos = 0;
+	return o;
+}
\ No newline at end of file
diff --git a/boot/fn.h b/boot/fn.h
index 1231d2a..faa32d0 100644
--- a/boot/fn.h
+++ b/boot/fn.h
@@ -11,10 +11,17 @@ int comprobe(ConDev *d);
 int comgetc(int dev);
 void computc(int dev, int c);
 
+// fmt.c
+int fmtinstall(int c, Op (*f)(Op));
+char *doprint(char *p, char *ep, char *fmt, va_list ap);
+int strlen(char *s);
+
 // print.c
 void putchar(int c);
+void putstr(char *s, int l);
 int getchar(void);
-void print(const char *fmt, ...);
+int print(char *fmt, ...);
+int snprint(char *buf, int len, char *fmt, ...);
 
 // a20.c
 void a20up(void);
diff --git a/boot/mem.c b/boot/mem.c
index e0a23fe..7d2170f 100644
--- a/boot/mem.c
+++ b/boot/mem.c
@@ -42,13 +42,13 @@ dumpmem(BIOSmmap *m)
 	ulong tot = 0;
 
 	for(BIOSmmap *p=m; p->type != MAP_END; ++p){
-		print("MEM %u type %u size %lldKB at 0x%llx\n",
-			p-m, p->type, p->size/1024, p->addr);
+		print("MEM % 2ud type %ud size % 10udKB at %08x:%08x\n",
+			p-m, p->type, (uint)(p->size/1024), (uint)(p->addr>>32), (uint)p->addr);
 		if(p->type == MAP_FREE)
 			tot += p->size/1024;
 	}
-	print("RAM low:%dKB high:%dKB\n", cnvmem, extmem);	
-	print("Total free memory: %dKB\n", tot);
+	print("RAM low:%udKB high:%udKB\n", cnvmem, extmem);
+	print("Total free memory: %udKB\n", tot);
 }
 
 static int
@@ -70,13 +70,12 @@ memprobe(void)
 	m->type = MAP_END;
 	for(m = biosmmap; m->type != MAP_END; ++m){
 		if(m->type != MAP_FREE || m->size <= 0)
-			continue;	
+			continue;
 		if(m->addr < IOMEM_BEGIN)
 			cnvmem = MAX(cnvmem, m->addr + m->size)/1024;
 		if(m->addr >= IOMEM_END)
 			extmem += m->size/1024;
 	}
 	dumpmem(biosmmap);
-	print("A20:%d", isa20done());
-}
-
+	print("A20:%s\n", isa20done() ? "ok" : "no");
+}
\ No newline at end of file
diff --git a/boot/print.c b/boot/print.c
index 647e82d..4ef3644 100644
--- a/boot/print.c
+++ b/boot/print.c
@@ -2,61 +2,42 @@
 #include "dat.h"
 #include "fn.h"
 
-#define TABWIDTH 4
+#define BUFSIZE 1024
 
-static void conputc(int c);
+static void conputc(int);
 static int congetc(void);
-static void doprint(void (*put)(int), const char *fmt, va_list ap);
-static void putint(void (*put)(int), int n, const char *sym, int base);
-static int pos = 0;
 
-void
-print(const char *fmt, ...)
+int
+print(char *fmt, ...)
 {
+	char buf[BUFSIZE], *p;
 	va_list args;
 
 	va_start(args, fmt);
-	doprint(putchar, fmt, args);
+	p = doprint(buf, buf+sizeof(buf), fmt, args);
 	va_end(args);
+	putstr(buf, p-buf);
+	return p-buf;
 }
 
-static void
-doprint(void (*put)(int), const char *s, va_list ap)
+int
+snprint(char *buf, int len, char *fmt, ...)
 {
-	while(*s){
-		if(*s != '%'){
-			put(*s++);
-			continue;
-		}
-		++s;
-		switch(*s){
-		case 'd':
-			putint(put, va_arg(ap,int), "0123456789", 10);
-			break;
-		case 'x':
-			putint(put, va_arg(ap,int), "0123456789abcdef", 16);
-			break;
-		case 'X':
-			putint(put, va_arg(ap,int), "0123456789ABCDEF", 16);
-			break;
-		case 's':
-			for(char *p=va_arg(ap,char*); *p; ++p)
-				put(*p);
-			break;
-		default:
-			return;
-		}
-		++s;
-	}
-}
+	char *p;
+	va_list args;
 
+	va_start(args, fmt);
+	p = doprint(buf, buf+len, fmt, args);
+	va_end(args);
+	return p-buf;
+}
 
 int
 getchar(void)
 {
 	int c;
 
-	c = congetc();	
+	c = congetc();
 	if(c == '\r')
 		c = '\n';
 	if((c < ' ' && c != '\n') || c == '\177')
@@ -65,6 +46,13 @@ getchar(void)
 	return c;
 }
 
+void
+putstr(char *s, int l)
+{
+	while(l--)
+		putchar(*s++);
+}
+
 void
 putchar(int c)
 {
@@ -72,24 +60,20 @@ putchar(int c)
 	case '\177':
 		conputc('\b');
 		conputc(' ');
+		break;
 	case '\b':
 		conputc('\b');
-		if(pos > 0)
-			--pos;
 		break;
 	case '\t':
-		do{
+		for(int i = 0; i < TABWIDTH; ++i)
 			conputc(' ');
-		}while(++pos % TABWIDTH);
 		break;
 	case '\n':
 	case '\r':
 		conputc(c);
-		pos = 0;
 		break;
 	default:
 		conputc(c);
-		++pos;
 		break;
 	}	
 }
@@ -108,20 +92,4 @@ static int
 congetc(void)
 {
 	return con->getc(con->dev);
-}
-
-static void
-putint(void (*put)(int), int n, const char *sym, int base)
-{
-	int i;
-	char buf[16];
-
-	i = 0;
-	do{
-		buf[i++] = n%base;
-		n /= base;
-	}while(n);
-	do{
-		put((int)sym[(int)buf[--i]]);
-	}while(i);
 }
\ No newline at end of file