diff --git a/src/printf.c b/src/printf.c
new file mode 100644
index 0000000..385df9b
--- /dev/null
+++ b/src/printf.c
@@ -0,0 +1,151 @@
+#include "config.h"
+#include "printf.h"
+
+// output stream
+static index_t _stdout=1;
+
+/*
+  Important: Output channel can be busy/full!
+  AVAILBYTE(od)==0
+*/
+INLINE void print_char(char c) {
+  OUTBYTE(_stdout,c);
+}
+
+
+void print_int(int i) {
+  if (i < 0) {
+    OUTBYTE(_stdout,'-');
+    i = -i;
+  }
+  if (i / 10) print_int(i / 10);
+  OUTBYTE(_stdout,i % 10 + '0');
+}
+
+char* sprint_int(char *buf, int i) {
+  if (i < 0) {
+    *buf='-';
+    i = -i;
+    buf++;
+  }
+  if (i / 10) buf=sprint_int(buf,i / 10);
+  *buf=i % 10 + '0';
+  buf++;
+  return buf;
+}
+
+
+void print_uint_hex(int i) {
+  if (i / 16) print_uint_hex(i / 16);
+  OUTBYTE(_stdout,i % 16 > 9? 'A'+(i%16)-10: (i%16) + '0');
+}
+
+void print_uint(unsigned int i) {
+  if (i / 10) print_uint(i / 10);
+  OUTBYTE(_stdout,i % 10 + '0');
+}
+
+#if HAS_FLOAT==0
+void print_number(number_t x) {
+  print_int((int)x);
+}
+#else
+  // TODO
+#endif
+
+/*
+  returns number of written array elements
+  returns zero or negative number if out channel is blocked
+*/
+int print_array(number_t *x,index_t len) {
+  int n=0;
+  while (len) { 
+    print_number(*x); 
+    x++;len--; 
+    n++; 
+  }
+  return n;
+}
+
+/*
+  returns number of written array elements
+  returns zero or negative number if out channel is blocked
+*/
+int print_string(char *s) {
+  int n=0;
+  while (*s) {
+    OUTBYTE(_stdout,*s++);
+    n++;
+  }
+  return n;
+}
+
+void print_format(char *format, ...) {
+  void **arg = (void **) &format + 1;
+  for (char *p = format; *p; p++) {
+    if (*p != '%') {
+        OUTBYTE(_stdout,*p);
+        continue;
+    }
+    switch (*++p) {
+      case 'd':
+          print_int(*(int *) arg++);
+          break;
+      case 'x':
+          print_uint_hex(*(int *) arg++);
+          break;
+      case 'u':
+          print_uint(*(unsigned int *) arg++);
+          break;
+      case 'c':
+          OUTBYTE(_stdout,*(char *) arg++);
+          break;
+      case 's':
+          print_string(*(char **) arg++);
+          break;
+      case '%':
+          OUTBYTE(_stdout,'%');
+          break;
+      default:
+          OUTBYTE(_stdout,*p);
+          break;
+    }
+  }
+}
+
+
+/*
+ buffer versions supporting up and down growing cyclic buffers
+ dir=1: [0,1,..,size-1]
+ dir=-1 : [size-1,size-2,..,0]
+ dir=-2 : [size-1,size-2,..,size/2]
+*/
+int bprint_char(char *buf, int off, int size, int dir, char c) {
+  buf[off]=c;
+  if (dir==1) off=(off+1)%size;
+  else if (dir==-1) off=off==0?size-1:off-1;
+  else /*-2*/ off=off==size/2?size-1:off-1;
+  return off;
+}
+int bprint_int(char *buf, int off, int size, int dir, int i) {
+  if (i < 0) {
+    buf[off]='-';
+    i = -i;
+    if (dir==1) off=(off+1)%size;
+    else if (dir==-1) off=off==0?size-1:off-1;
+    else /*-2*/ off=off==size/2?size-1:off-1;
+  }
+  if (i / 10) off=bprint_int(buf,off,size,dir, i / 10);
+  buf[off]=i % 10 + '0';
+  if (dir==1) off=(off+1)%size;
+  else if (dir==-1) off=off==0?size-1:off-1;
+  else /*-2*/ off=off==size/2?size-1:off-1;
+  return off;
+}
+
+
+/*
+  Set standard output channel (default 1)
+*/
+index_t print_stdout(index_t handle) { index_t old=_stdout; _stdout=handle; return old; }
+