diff --git a/c/c.go b/c/c.go
index fcff0826..f035ff48 100644
--- a/c/c.go
+++ b/c/c.go
@@ -109,6 +109,12 @@ func Printf(format *Char, __llgo_va_list ...any) Int
 //go:linkname Fprintf C.fprintf
 func Fprintf(fp FilePtr, format *Char, __llgo_va_list ...any) Int
 
+//go:linkname Fwrite C.fwrite
+func Fwrite(data Pointer, size, count uintptr, fp FilePtr) uintptr
+
+//go:linkname Fputc C.fputc
+func Fputc(c Int, fp FilePtr) Int
+
 // -----------------------------------------------------------------------------
 
 //go:linkname Time C.time
diff --git a/internal/runtime/llgo_autogen.lla b/internal/runtime/llgo_autogen.lla
index e6491d05..61566d86 100644
Binary files a/internal/runtime/llgo_autogen.lla and b/internal/runtime/llgo_autogen.lla differ
diff --git a/internal/runtime/print.go b/internal/runtime/print.go
deleted file mode 100644
index aef6c02e..00000000
--- a/internal/runtime/print.go
+++ /dev/null
@@ -1,176 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package runtime
-
-import (
-	"unsafe"
-
-	"github.com/goplus/llgo/c"
-)
-
-// The compiler knows that a print of a value of this type
-// should use printhex instead of printuint (decimal).
-func bytes(s string) (ret []byte) {
-	rp := (*Slice)(unsafe.Pointer(&ret))
-	sp := (*String)(unsafe.Pointer(&s))
-	rp.data = sp.data
-	rp.len = sp.len
-	rp.cap = sp.len
-	return
-}
-
-func gwrite(b []byte) {
-	if len(b) == 0 {
-		return
-	}
-	for _, v := range b {
-		c.Fprintf(c.Stderr, c.Str("%c"), v)
-	}
-}
-
-func PrintByte(v byte) {
-	c.Fprintf(c.Stderr, c.Str("%c"), v)
-}
-
-func PrintBool(v bool) {
-	if v {
-		PrintString("true")
-	} else {
-		PrintString("false")
-	}
-}
-
-func PrintFloat(v float64) {
-	switch {
-	case v != v:
-		PrintString("NaN")
-		return
-	case v+v == v && v > 0:
-		PrintString("+Inf")
-		return
-	case v+v == v && v < 0:
-		PrintString("-Inf")
-		return
-	}
-
-	const n = 7 // digits printed
-	var buf [n + 7]byte
-	buf[0] = '+'
-	e := 0 // exp
-	if v == 0 {
-		if 1/v < 0 {
-			buf[0] = '-'
-		}
-	} else {
-		if v < 0 {
-			v = -v
-			buf[0] = '-'
-		}
-
-		// normalize
-		for v >= 10 {
-			e++
-			v /= 10
-		}
-		for v < 1 {
-			e--
-			v *= 10
-		}
-
-		// round
-		h := 5.0
-		for i := 0; i < n; i++ {
-			h /= 10
-		}
-		v += h
-		if v >= 10 {
-			e++
-			v /= 10
-		}
-	}
-
-	// format +d.dddd+edd
-	for i := 0; i < n; i++ {
-		s := int(v)
-		buf[i+2] = byte(s + '0')
-		v -= float64(s)
-		v *= 10
-	}
-	buf[1] = buf[2]
-	buf[2] = '.'
-
-	buf[n+2] = 'e'
-	buf[n+3] = '+'
-	if e < 0 {
-		e = -e
-		buf[n+3] = '-'
-	}
-
-	buf[n+4] = byte(e/100) + '0'
-	buf[n+5] = byte(e/10)%10 + '0'
-	buf[n+6] = byte(e%10) + '0'
-	gwrite(buf[:])
-}
-
-// func PrintComplex(c complex128) {
-// 	print("(", real(c), imag(c), "i)")
-// }
-
-func PrintUint(v uint64) {
-	var buf [100]byte
-	i := len(buf)
-	for i--; i > 0; i-- {
-		buf[i] = byte(v%10 + '0')
-		if v < 10 {
-			break
-		}
-		v /= 10
-	}
-	gwrite(buf[i:])
-}
-
-func PrintInt(v int64) {
-	if v < 0 {
-		PrintString("-")
-		v = -v
-	}
-	PrintUint(uint64(v))
-}
-
-func PrintHex(v uint64) {
-	const dig = "0123456789abcdef"
-	var buf [100]byte
-	i := len(buf)
-	for i--; i > 0; i-- {
-		buf[i] = dig[v%16]
-		if v < 16 && len(buf)-i >= 0 {
-			break
-		}
-		v /= 16
-	}
-	i--
-	buf[i] = 'x'
-	i--
-	buf[i] = '0'
-	gwrite(buf[i:])
-}
-
-func PrintPointer(p unsafe.Pointer) {
-	PrintHex(uint64(uintptr(p)))
-}
-
-func PrintString(s string) {
-	gwrite(bytes(s))
-}
-
-func PrintSlice(s Slice) {
-	sp := (*Slice)(unsafe.Pointer(&s))
-	print("[", s.len, "/", s.cap, "]")
-	PrintPointer(sp.data)
-}
-
-func PrintIface(i iface) {
-	print("(", i.tab, ",", i.data, ")")
-}
diff --git a/internal/runtime/z_print.go b/internal/runtime/z_print.go
new file mode 100644
index 00000000..2bb01541
--- /dev/null
+++ b/internal/runtime/z_print.go
@@ -0,0 +1,71 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+func PrintByte(v byte) {
+	c.Fputc(c.Int(v), c.Stderr)
+}
+
+func PrintBool(v bool) {
+	if v {
+		c.Fprintf(c.Stderr, c.Str("true"))
+	} else {
+		c.Fprintf(c.Stderr, c.Str("false"))
+	}
+}
+
+func PrintFloat(v float64) {
+	switch { // TODO(xsw): does c.Fprintf support these special cases?
+	case v != v:
+		c.Fprintf(c.Stderr, c.Str("NaN"))
+		return
+	case v+v == v:
+		if v > 0 {
+			c.Fprintf(c.Stderr, c.Str("+Inf"))
+		} else if v < 0 {
+			c.Fprintf(c.Stderr, c.Str("-Inf"))
+		}
+		return
+	}
+	c.Fprintf(c.Stderr, c.Str("%g"), v)
+}
+
+// func PrintComplex(c complex128) {
+// 	print("(", real(c), imag(c), "i)")
+// }
+
+func PrintUint(v uint64) {
+	c.Fprintf(c.Stderr, c.Str("%llu"), v)
+}
+
+func PrintInt(v int64) {
+	c.Fprintf(c.Stderr, c.Str("%lld"), v)
+}
+
+func PrintHex(v uint64) {
+	c.Fprintf(c.Stderr, c.Str("%llx"), v)
+}
+
+func PrintPointer(p unsafe.Pointer) {
+	c.Fprintf(c.Stderr, c.Str("%p"), p)
+}
+
+func PrintString(s String) {
+	c.Fwrite(s.data, 1, uintptr(s.len), c.Stderr)
+}
+
+func PrintSlice(s Slice) {
+	print("[", s.len, "/", s.cap, "]", s.data)
+}
+
+func PrintIface(i Interface) {
+	print("(", i.tab, ",", i.data, ")")
+}