diff --git a/lang/cem/libcc.ansi/headers/ack/config.h b/lang/cem/libcc.ansi/headers/ack/config.h
index 2ee784213..41e9bc3b6 100644
--- a/lang/cem/libcc.ansi/headers/ack/config.h
+++ b/lang/cem/libcc.ansi/headers/ack/config.h
@@ -63,4 +63,9 @@
 #define ACKCONF_WANT_STDIO 1
 #endif
 
+#ifndef ACKCONF_WANT_EMULATED_FILE
+/* Implement FILE* on top of read()/write() file descriptors. */
+#define ACKCONF_WANT_EMULATED_FILE 1
+#endif
+
 #endif
diff --git a/lang/cem/libcc.ansi/headers/ack/emufile.h b/lang/cem/libcc.ansi/headers/ack/emufile.h
new file mode 100644
index 000000000..6e799b47b
--- /dev/null
+++ b/lang/cem/libcc.ansi/headers/ack/emufile.h
@@ -0,0 +1,59 @@
+#ifndef ACK_EMUFILE_H
+#define ACK_EMUFILE_H
+
+/*
+ * Focus point of all stdio activity.
+ */
+struct FILE {
+	int		_count;
+	int		_fd;
+	int		_flags;
+	int		_bufsiz;
+	unsigned char	*_buf;
+	unsigned char	*_ptr;
+};
+
+#define	_IOFBF		0x000
+#define	_IOREAD		0x001
+#define	_IOWRITE	0x002
+#define	_IONBF		0x004
+#define	_IOMYBUF	0x008
+#define	_IOEOF		0x010
+#define	_IOERR		0x020
+#define	_IOLBF		0x040
+#define	_IOREADING	0x080
+#define _IOWRITING	0x100
+#define	_IOAPPEND	0x200
+
+#define	BUFSIZ      1024
+
+#define	FOPEN_MAX	20
+extern FILE	*__iotab[FOPEN_MAX];
+
+#define	FILENAME_MAX 255
+#define	TMP_MAX     999
+#define	L_tmpnam    (sizeof("/tmp/") + 15)
+#define ACK_TMP_PREFIX "/tmp/tmp."
+
+extern int __fillbuf(FILE *_stream);
+extern int __flushbuf(int _c, FILE *_stream);
+
+#define	getchar()	getc(stdin)
+#define	putchar(c)	putc(c,stdout)
+#define	getc(p)		(--(p)->_count >= 0 ? (int) (*(p)->_ptr++) : \
+				__fillbuf(p))
+#define	putc(c, p)	(--(p)->_count >= 0 ? \
+			 (int) (*(p)->_ptr++ = (c)) : \
+			 __flushbuf((c),(p)))
+
+#define	feof(p)		(((p)->_flags & _IOEOF) != 0)
+#define	ferror(p)	(((p)->_flags & _IOERR) != 0)
+#define clearerr(p)	((p)->_flags &= ~(_IOERR|_IOEOF))
+
+/* Non-standard extensions */
+
+extern int fileno(FILE *_stream);
+extern FILE* fdopen(int fildes, const char *type);
+#define	fileno(stream) ((stream)->_fd)
+
+#endif
diff --git a/lang/cem/libcc.ansi/headers/stdio.h b/lang/cem/libcc.ansi/headers/stdio.h
index 52f286f20..7988c397d 100644
--- a/lang/cem/libcc.ansi/headers/stdio.h
+++ b/lang/cem/libcc.ansi/headers/stdio.h
@@ -10,30 +10,14 @@
 #define	_STDIO_H
 
 #include <stddef.h>
+#include <stdarg.h>
+#include <ack/config.h>
 
-/*
- * Focus point of all stdio activity.
- */
-typedef struct __iobuf {
-	int		_count;
-	int		_fd;
-	int		_flags;
-	int		_bufsiz;
-	unsigned char	*_buf;
-	unsigned char	*_ptr;
-} FILE;
+/* Public stdio entry points. */
 
-#define	_IOFBF		0x000
-#define	_IOREAD		0x001
-#define	_IOWRITE	0x002
-#define	_IONBF		0x004
-#define	_IOMYBUF	0x008
-#define	_IOEOF		0x010
-#define	_IOERR		0x020
-#define	_IOLBF		0x040
-#define	_IOREADING	0x080
-#define _IOWRITING	0x100
-#define	_IOAPPEND	0x200
+typedef struct FILE FILE;
+
+#define	EOF         (-1)
 
 #define	SEEK_SET    0
 #define	SEEK_CUR    1
@@ -43,18 +27,8 @@ typedef struct __iobuf {
 #define	stdout      (&__stdout)
 #define	stderr      (&__stderr)
 
-#define	BUFSIZ      1024
-#define	EOF         (-1)
-
-#define	FOPEN_MAX	20
-
-#define	FILENAME_MAX 255
-#define	TMP_MAX     999
-#define	L_tmpnam    (sizeof("/tmp/") + 15)
-
 typedef long int fpos_t;
 
-extern FILE	*__iotab[FOPEN_MAX];
 extern FILE	__stdin, __stdout, __stderr;
 
 extern int	remove(const char *_filename);
@@ -69,6 +43,7 @@ extern void	setbuf(FILE *_stream, char *_buf);
 extern int	setvbuf(FILE *_stream, char *_buf, int _mode, size_t _size);
 extern int	fprintf(FILE *_stream, const char *_format, ...);
 extern int	fscanf(FILE *_stream, const char *_format, ...);
+extern int	vfscanf(FILE *_stream, const char *_format, va_list ap);
 extern int	printf(const char *_format, ...);
 extern int	scanf(const char *_format, ...);
 extern int	sprintf(char *_s, const char *_format, ...);
@@ -76,8 +51,8 @@ extern int	snprintf(char *_s, size_t _len, const char *_format, ...);
 extern int	sscanf(const char *_s, const char *_format, ...);
 extern int	vfprintf(FILE *_stream, const char *_format, char *_arg);
 extern int	vprintf(const char *_format, char *_arg);
-extern int	vsprintf(char *_s, const char *_format, char *_arg);
-extern int	vsnprintf(char *_s, size_t _len, const char *_format, char *_arg);
+extern int	vsprintf(char *_s, const char *_format, va_list ap);
+extern int	vsnprintf(char *_s, size_t _len, const char *_format, va_list ap);
 extern int	fgetc(FILE *_stream);
 extern char	*fgets(char *_s, int _n, FILE *_stream);
 extern int	fputc(int _c, FILE *_stream);
@@ -101,25 +76,10 @@ extern int	feof(FILE *_stream);
 extern int	ferror(FILE *_stream);
 extern void	perror(const char *_s);
 
-extern int __fillbuf(FILE *_stream);
-extern int __flushbuf(int _c, FILE *_stream);
-
-#define	getchar()	getc(stdin)
-#define	putchar(c)	putc(c,stdout)
-#define	getc(p)		(--(p)->_count >= 0 ? (int) (*(p)->_ptr++) : \
-				__fillbuf(p))
-#define	putc(c, p)	(--(p)->_count >= 0 ? \
-			 (int) (*(p)->_ptr++ = (c)) : \
-			 __flushbuf((c),(p)))
-
-#define	feof(p)		(((p)->_flags & _IOEOF) != 0)
-#define	ferror(p)	(((p)->_flags & _IOERR) != 0)
-#define clearerr(p)	((p)->_flags &= ~(_IOERR|_IOEOF))
-
-/* Non-standard extensions */
-
-extern int fileno(FILE *_stream);
-extern FILE* fdopen(int fildes, const char *type);
-#define	fileno(stream) ((stream)->_fd)
+#if ACKCONF_WANT_EMULATED_FILE
+#include <ack/emufile.h>
+#else
+#include <ack/file.h>
+#endif
 
 #endif	/* _STDIO_H */
diff --git a/lang/cem/libcc.ansi/sys/stdio/data.c b/lang/cem/libcc.ansi/sys/stdio/data.c
index ccf1664ce..aba91557a 100644
--- a/lang/cem/libcc.ansi/sys/stdio/data.c
+++ b/lang/cem/libcc.ansi/sys/stdio/data.c
@@ -5,19 +5,19 @@
 
 #include <stdio.h>
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
-struct __iobuf __stdin = {
+struct FILE __stdin = {
 	0, 0, _IOREAD, 0,
 	(unsigned char*)NULL, (unsigned char*)NULL,
 };
 
-struct __iobuf __stdout = {
+struct FILE __stdout = {
 	0, 1, _IOWRITE, 0,
 	(unsigned char*)NULL, (unsigned char*)NULL,
 };
 
-struct __iobuf __stderr = {
+struct FILE __stderr = {
 	0, 2, _IOWRITE | _IOLBF, 0,
 	(unsigned char*)NULL, (unsigned char*)NULL,
 };
diff --git a/lang/cem/libcc.ansi/sys/stdio/doprnt.c b/lang/cem/libcc.ansi/sys/stdio/doprnt.c
index 9f74c7659..8c97fb5a4 100644
--- a/lang/cem/libcc.ansi/sys/stdio/doprnt.c
+++ b/lang/cem/libcc.ansi/sys/stdio/doprnt.c
@@ -157,7 +157,7 @@ o_print(va_list* ap, int flags, char* s, char c, int precision, int is_signed)
 	return s;
 }
 
-int _doprnt(register const char* fmt, va_list ap, FILE* stream)
+int _doprnt(register const char* fmt, va_list ap, void (*put)(int))
 {
 	register char* s;
 	register int j;
@@ -176,7 +176,7 @@ int _doprnt(register const char* fmt, va_list ap, FILE* stream)
 				PUTC('\r');
 			}
 #endif
-			PUTC(c);
+			put(c);
 			nrchars++;
 			continue;
 		}
@@ -263,7 +263,7 @@ int _doprnt(register const char* fmt, va_list ap, FILE* stream)
 					nrchars++;
 				}
 #endif
-				PUTC(c);
+				put(c);
 				nrchars++;
 				continue;
 			case 'n':
@@ -366,32 +366,32 @@ int _doprnt(register const char* fmt, va_list ap, FILE* stream)
 					{
 						j--;
 						nrchars++;
-						PUTC(*s1++);
+						put(*s1++);
 					}
 					else
 					{
 						j -= 2;
 						nrchars += 2;
-						PUTC(*s1++);
-						PUTC(*s1++);
+						put(*s1++);
+						put(*s1++);
 					}
 				}
 				do
 				{
-					PUTC(zfill);
+					put(zfill);
 				} while (--i);
 			}
 
 		nrchars += j;
 		while (--j >= 0)
 		{
-			PUTC(*s1++);
+			put(*s1++);
 		}
 
 		if (i > 0)
 			nrchars += i;
 		while (--i >= 0)
-			PUTC(zfill);
+			put(zfill);
 	}
 	return nrchars;
 }
diff --git a/lang/cem/libcc.ansi/sys/stdio/doscan.c b/lang/cem/libcc.ansi/sys/stdio/doscan.c
index 3a1076bad..45748427e 100644
--- a/lang/cem/libcc.ansi/sys/stdio/doscan.c
+++ b/lang/cem/libcc.ansi/sys/stdio/doscan.c
@@ -33,8 +33,7 @@ static char inp_buf[NUMLEN];
  * is then set to 0, so strtol() will get the right argument.
  */
 static char*
-o_collect(register int c, register FILE* stream, char type,
-    int width, int* basep)
+o_collect(register int c, char type, int width, int* basep, int (*get)(void), void (*unget)(int c))
 {
 	register char* bufp = inp_buf;
 	register int base;
@@ -63,14 +62,14 @@ o_collect(register int c, register FILE* stream, char type,
 	{
 		*bufp++ = c;
 		if (--width)
-			c = getc(stream);
+			c = get();
 	}
 
 	if (width && c == '0' && base == 16)
 	{
 		*bufp++ = c;
 		if (--width)
-			c = getc(stream);
+			c = get();
 		if (c != 'x' && c != 'X')
 		{
 			if (type == 'i')
@@ -80,7 +79,7 @@ o_collect(register int c, register FILE* stream, char type,
 		{
 			*bufp++ = c;
 			if (--width)
-				c = getc(stream);
+				c = get();
 		}
 	}
 	else if (type == 'i')
@@ -95,14 +94,14 @@ o_collect(register int c, register FILE* stream, char type,
 		{
 			*bufp++ = c;
 			if (--width)
-				c = getc(stream);
+				c = get();
 		}
 		else
 			break;
 	}
 
 	if (width && c != EOF)
-		ungetc(c, stream);
+		unget(c);
 	if (type == 'i')
 		base = 0;
 	*basep = base;
@@ -120,7 +119,7 @@ o_collect(register int c, register FILE* stream, char type,
  * numbers to be passed to strtod(). (e.g. 1.3e+)
  */
 static char*
-f_collect(register int c, register FILE* stream, register int width)
+f_collect(register int c, register int width, int (*get)(void), void (*unget)(int c))
 {
 	register char* bufp = inp_buf;
 	int digit_seen = 0;
@@ -129,7 +128,7 @@ f_collect(register int c, register FILE* stream, register int width)
 	{
 		*bufp++ = c;
 		if (--width)
-			c = getc(stream);
+			c = get();
 	}
 
 	while (width && isdigit(c))
@@ -137,26 +136,26 @@ f_collect(register int c, register FILE* stream, register int width)
 		digit_seen++;
 		*bufp++ = c;
 		if (--width)
-			c = getc(stream);
+			c = get();
 	}
 	if (width && c == '.')
 	{
 		*bufp++ = c;
 		if (--width)
-			c = getc(stream);
+			c = get();
 		while (width && isdigit(c))
 		{
 			digit_seen++;
 			*bufp++ = c;
 			if (--width)
-				c = getc(stream);
+				c = get();
 		}
 	}
 
 	if (!digit_seen)
 	{
 		if (width && c != EOF)
-			ungetc(c, stream);
+			unget(c);
 		return inp_buf - 1;
 	}
 	else
@@ -166,30 +165,30 @@ f_collect(register int c, register FILE* stream, register int width)
 	{
 		*bufp++ = c;
 		if (--width)
-			c = getc(stream);
+			c = get();
 		if (width && (c == '+' || c == '-'))
 		{
 			*bufp++ = c;
 			if (--width)
-				c = getc(stream);
+				c = get();
 		}
 		while (width && isdigit(c))
 		{
 			digit_seen++;
 			*bufp++ = c;
 			if (--width)
-				c = getc(stream);
+				c = get();
 		}
 		if (!digit_seen)
 		{
 			if (width && c != EOF)
-				ungetc(c, stream);
+				unget(c);
 			return inp_buf - 1;
 		}
 	}
 
 	if (width && c != EOF)
-		ungetc(c, stream);
+		unget(c);
 	*bufp = '\0';
 	return bufp - 1;
 }
@@ -199,7 +198,7 @@ f_collect(register int c, register FILE* stream, register int width)
  * the routine that does the scanning 
  */
 
-int _doscan(register FILE* stream, const char* format, va_list ap)
+int _doscan(const char* format, va_list ap, int (*get)(void), void (*unget)(int c))
 {
 	int done = 0; /* number of items done */
 	int nrchars = 0; /* number of characters read */
@@ -226,15 +225,15 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 		{
 			while (isspace(*format))
 				format++; /* skip whitespace */
-			ic = getc(stream);
+			ic = get();
 			nrchars++;
 			while (isspace(ic))
 			{
-				ic = getc(stream);
+				ic = get();
 				nrchars++;
 			}
 			if (ic != EOF)
-				ungetc(ic, stream);
+				unget(ic);
 			nrchars--;
 		}
 		if (!*format)
@@ -242,12 +241,12 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 
 		if (*format != '%')
 		{
-			ic = getc(stream);
+			ic = get();
 			nrchars++;
 			if (ic != *format++)
 			{
 				if (ic != EOF)
-					ungetc(ic, stream);
+					unget(ic);
 				nrchars--;
 				break; /* error */
 			}
@@ -256,7 +255,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 		format++;
 		if (*format == '%')
 		{
-			ic = getc(stream);
+			ic = get();
 			nrchars++;
 			if (ic == '%')
 			{
@@ -299,7 +298,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 		{
 			do
 			{
-				ic = getc(stream);
+				ic = get();
 				nrchars++;
 			} while (isspace(ic));
 			if (ic == EOF)
@@ -307,7 +306,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 		}
 		else if (kind != 'n')
 		{ /* %c or %[ */
-			ic = getc(stream);
+			ic = get();
 			if (ic == EOF)
 				break; /* outer while */
 			nrchars++;
@@ -344,7 +343,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 				if (!width)
 					return done;
 
-				str = o_collect(ic, stream, kind, width, &base);
+				str = o_collect(ic, kind, width, &base, get, unget);
 				if (str < inp_buf
 				    || (str == inp_buf
 				           && (*str == '-'
@@ -385,7 +384,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 						*str++ = (char)ic;
 					if (--width)
 					{
-						ic = getc(stream);
+						ic = get();
 						nrchars++;
 					}
 				}
@@ -393,7 +392,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 				if (width)
 				{
 					if (ic != EOF)
-						ungetc(ic, stream);
+						unget(ic);
 					nrchars--;
 				}
 				break;
@@ -411,7 +410,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 						*str++ = (char)ic;
 					if (--width)
 					{
-						ic = getc(stream);
+						ic = get();
 						nrchars++;
 					}
 				}
@@ -421,7 +420,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 				if (width)
 				{
 					if (ic != EOF)
-						ungetc(ic, stream);
+						unget(ic);
 					nrchars--;
 				}
 				break;
@@ -468,7 +467,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 				if (!*format || !(Xtable[ic] ^ reverse))
 				{
 					if (ic != EOF)
-						ungetc(ic, stream);
+						unget(ic);
 					return done;
 				}
 
@@ -481,7 +480,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 						*str++ = (char)ic;
 					if (--width)
 					{
-						ic = getc(stream);
+						ic = get();
 						nrchars++;
 					}
 				} while (width && ic != EOF && (Xtable[ic] ^ reverse));
@@ -489,7 +488,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 				if (width)
 				{
 					if (ic != EOF)
-						ungetc(ic, stream);
+						unget(ic);
 					nrchars--;
 				}
 				if (!(flags & FL_NOASSIGN))
@@ -508,7 +507,7 @@ int _doscan(register FILE* stream, const char* format, va_list ap)
 
 				if (!width)
 					return done;
-				str = f_collect(ic, stream, width);
+				str = f_collect(ic, width, get, unget);
 
 				if (str < inp_buf
 				    || (str == inp_buf
diff --git a/lang/cem/libcc.ansi/sys/stdio/fclose.c b/lang/cem/libcc.ansi/sys/stdio/fclose.c
index 9a56b4cfe..2410220be 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fclose.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fclose.c
@@ -8,7 +8,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int fclose(FILE* fp)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/fdopen.c b/lang/cem/libcc.ansi/sys/stdio/fdopen.c
index 084d39c14..20fabd5fb 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fdopen.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fdopen.c
@@ -7,7 +7,7 @@
 #include <stdlib.h>
 #include "../stdio/loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 FILE* fdopen(int fd, const char* mode)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/fflush.c b/lang/cem/libcc.ansi/sys/stdio/fflush.c
index f0f53bb25..f38be1bd1 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fflush.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fflush.c
@@ -8,7 +8,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int fflush(FILE* stream)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/fileno.c b/lang/cem/libcc.ansi/sys/stdio/fileno.c
index e42608845..36e2b8bb9 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fileno.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fileno.c
@@ -5,7 +5,7 @@
 
 #include <stdio.h>
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int(fileno)(FILE* stream)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/fillbuf.c b/lang/cem/libcc.ansi/sys/stdio/fillbuf.c
index 75187edac..019d138fc 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fillbuf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fillbuf.c
@@ -8,7 +8,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int __fillbuf(register FILE* stream)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/flushbuf.c b/lang/cem/libcc.ansi/sys/stdio/flushbuf.c
index 81325d3a6..aba0a7c4c 100644
--- a/lang/cem/libcc.ansi/sys/stdio/flushbuf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/flushbuf.c
@@ -8,7 +8,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 static int
 do_write(int d, char* buf, int nbytes)
diff --git a/lang/cem/libcc.ansi/sys/stdio/fopen.c b/lang/cem/libcc.ansi/sys/stdio/fopen.c
index ce8c5634e..24e1537b9 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fopen.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fopen.c
@@ -10,7 +10,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 #define PMODE 0666
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/fprintf.c b/lang/cem/libcc.ansi/sys/stdio/fprintf.c
index 3085bf96a..9db8b74ee 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fprintf.c
@@ -15,9 +15,7 @@ int fprintf(FILE* stream, const char* format, ...)
 	int retval;
 
 	va_start(ap, format);
-
-	retval = _doprnt(format, ap, stream);
-
+	retval = vfprintf(stream, format, ap);
 	va_end(ap);
 
 	return retval;
diff --git a/lang/cem/libcc.ansi/sys/stdio/freopen.c b/lang/cem/libcc.ansi/sys/stdio/freopen.c
index 255e04cb6..d4bb4abf8 100644
--- a/lang/cem/libcc.ansi/sys/stdio/freopen.c
+++ b/lang/cem/libcc.ansi/sys/stdio/freopen.c
@@ -9,7 +9,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 #define PMODE 0666
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/fscanf.c b/lang/cem/libcc.ansi/sys/stdio/fscanf.c
index b06d47253..8c006c85c 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fscanf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fscanf.c
@@ -15,9 +15,7 @@ int fscanf(FILE* stream, const char* format, ...)
 	int retval;
 
 	va_start(ap, format);
-
-	retval = _doscan(stream, format, ap);
-
+	retval = vfscanf(stream, format, ap);
 	va_end(ap);
 
 	return retval;
diff --git a/lang/cem/libcc.ansi/sys/stdio/fseek.c b/lang/cem/libcc.ansi/sys/stdio/fseek.c
index c1ecd5650..5b87a9b30 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fseek.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fseek.c
@@ -8,7 +8,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int fseek(FILE* stream, long int offset, int whence)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/ftell.c b/lang/cem/libcc.ansi/sys/stdio/ftell.c
index 8053a1de2..4728b201b 100644
--- a/lang/cem/libcc.ansi/sys/stdio/ftell.c
+++ b/lang/cem/libcc.ansi/sys/stdio/ftell.c
@@ -8,7 +8,7 @@
 #include <unistd.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 long ftell(FILE* stream)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/loc_incl.h b/lang/cem/libcc.ansi/sys/stdio/loc_incl.h
index b30d3272a..4d21923a2 100644
--- a/lang/cem/libcc.ansi/sys/stdio/loc_incl.h
+++ b/lang/cem/libcc.ansi/sys/stdio/loc_incl.h
@@ -10,8 +10,8 @@
 #define	io_testflag(p,x)	((p)->_flags & (x))
 
 #include	<stdarg.h>
-int _doprnt(const char *format, va_list ap, FILE *stream);
-int _doscan(FILE * stream, const char *format, va_list ap);
+int _doprnt(const char *format, va_list ap, void (*put)(int c));
+int _doscan(const char *format, va_list ap, int (*get)(void), void (*unget)(int c));
 char *_i_compute(unsigned long val, int base, char *s, int nrdigits);
 char *_f_print(va_list *ap, int flags, char *s, char c, int precision);
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/printf.c b/lang/cem/libcc.ansi/sys/stdio/printf.c
index 6b118c859..2042983e7 100644
--- a/lang/cem/libcc.ansi/sys/stdio/printf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/printf.c
@@ -15,9 +15,7 @@ int printf(const char* format, ...)
 	int retval;
 
 	va_start(ap, format);
-
-	retval = _doprnt(format, ap, stdout);
-
+	retval = vfprintf(stdout, format, ap);
 	va_end(ap);
 
 	return retval;
diff --git a/lang/cem/libcc.ansi/sys/stdio/scanf.c b/lang/cem/libcc.ansi/sys/stdio/scanf.c
index d52788084..3fb9875fc 100644
--- a/lang/cem/libcc.ansi/sys/stdio/scanf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/scanf.c
@@ -15,9 +15,7 @@ int scanf(const char* format, ...)
 	int retval;
 
 	va_start(ap, format);
-
-	retval = _doscan(stdin, format, ap);
-
+	retval = vfscanf(stdin, format, ap);
 	va_end(ap);
 
 	return retval;
diff --git a/lang/cem/libcc.ansi/sys/stdio/setbuf.c b/lang/cem/libcc.ansi/sys/stdio/setbuf.c
index 5ac3e8ece..866b2516d 100644
--- a/lang/cem/libcc.ansi/sys/stdio/setbuf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/setbuf.c
@@ -6,7 +6,7 @@
 #include <stdio.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 void setbuf(register FILE* stream, char* buf)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/setvbuf.c b/lang/cem/libcc.ansi/sys/stdio/setvbuf.c
index 1dfc6a0be..af203ef51 100644
--- a/lang/cem/libcc.ansi/sys/stdio/setvbuf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/setvbuf.c
@@ -7,7 +7,7 @@
 #include <stdlib.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int setvbuf(register FILE* stream, char* buf, int mode, size_t size)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/snprintf.c b/lang/cem/libcc.ansi/sys/stdio/snprintf.c
index 4ee372faa..99128e3d7 100644
--- a/lang/cem/libcc.ansi/sys/stdio/snprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/snprintf.c
@@ -9,22 +9,29 @@
 
 #if ACKCONF_WANT_STDIO
 
+static char* output_buffer;
+static size_t output_buffer_len;
+
+static void snprintf_putc(int c)
+{
+	if (output_buffer_len)
+	{
+		*output_buffer++ = c;
+		output_buffer_len--;
+	}
+}
+
 int snprintf(char* s, size_t len, const char* format, ...)
 {
 	va_list ap;
 	int retval;
-	FILE tmp_stream;
 
 	va_start(ap, format);
 
-	tmp_stream._fd = -1;
-	tmp_stream._flags = _IOWRITE + _IONBF + _IOWRITING;
-	tmp_stream._buf = (unsigned char*)s;
-	tmp_stream._ptr = (unsigned char*)s;
-	tmp_stream._count = len;
-
-	retval = _doprnt(format, ap, &tmp_stream);
-	putc('\0', &tmp_stream);
+	output_buffer = s;
+	output_buffer_len = len;
+	retval = _doprnt(format, ap, snprintf_putc);
+	snprintf_putc('\0');
 
 	va_end(ap);
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/sprintf.c b/lang/cem/libcc.ansi/sys/stdio/sprintf.c
index 3a116c0f4..e57d63ac1 100644
--- a/lang/cem/libcc.ansi/sys/stdio/sprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/sprintf.c
@@ -13,19 +13,9 @@ int sprintf(char* s, const char* format, ...)
 {
 	va_list ap;
 	int retval;
-	FILE tmp_stream;
 
 	va_start(ap, format);
-
-	tmp_stream._fd = -1;
-	tmp_stream._flags = _IOWRITE + _IONBF + _IOWRITING;
-	tmp_stream._buf = (unsigned char*)s;
-	tmp_stream._ptr = (unsigned char*)s;
-	tmp_stream._count = 32767;
-
-	retval = _doprnt(format, ap, &tmp_stream);
-	putc('\0', &tmp_stream);
-
+	retval = vsnprintf(s, 32767, format, ap);
 	va_end(ap);
 
 	return retval;
diff --git a/lang/cem/libcc.ansi/sys/stdio/sscanf.c b/lang/cem/libcc.ansi/sys/stdio/sscanf.c
index bd39100bd..76e96aa7b 100644
--- a/lang/cem/libcc.ansi/sys/stdio/sscanf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/sscanf.c
@@ -10,21 +10,32 @@
 
 #if ACKCONF_WANT_STDIO
 
+static const char* input_buffer;
+
+static int sscanf_getc(void)
+{
+	char c = *input_buffer;
+	if (c == 0)
+		return EOF;
+	input_buffer++;
+	return c;
+}
+
+static void sscanf_ungetc(int c)
+{
+	/* sscanf always ungets the last character read. */
+	input_buffer--;
+}
+
 int sscanf(const char* s, const char* format, ...)
 {
 	va_list ap;
 	int retval;
-	FILE tmp_stream;
 
 	va_start(ap, format);
 
-	tmp_stream._fd = -1;
-	tmp_stream._flags = _IOREAD + _IONBF + _IOREADING;
-	tmp_stream._buf = (unsigned char*)s;
-	tmp_stream._ptr = (unsigned char*)s;
-	tmp_stream._count = strlen(s);
-
-	retval = _doscan(&tmp_stream, format, ap);
+	input_buffer = s;
+	retval = _doscan(format, ap, sscanf_getc, sscanf_ungetc);
 
 	va_end(ap);
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/tmpfile.c b/lang/cem/libcc.ansi/sys/stdio/tmpfile.c
index e50fd0d35..384007aaa 100644
--- a/lang/cem/libcc.ansi/sys/stdio/tmpfile.c
+++ b/lang/cem/libcc.ansi/sys/stdio/tmpfile.c
@@ -13,7 +13,7 @@
 
 FILE* tmpfile(void)
 {
-	static char name_buffer[L_tmpnam] = "/tmp/tmp.";
+	static char name_buffer[L_tmpnam] = ACK_TMP_PREFIX;
 	static char* name = NULL;
 	FILE* file;
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/tmpnam.c b/lang/cem/libcc.ansi/sys/stdio/tmpnam.c
index 89fb9a4e3..e67276545 100644
--- a/lang/cem/libcc.ansi/sys/stdio/tmpnam.c
+++ b/lang/cem/libcc.ansi/sys/stdio/tmpnam.c
@@ -13,7 +13,7 @@
 
 char* tmpnam(char* s)
 {
-	static char name_buffer[L_tmpnam] = "/tmp/tmp.";
+	static char name_buffer[L_tmpnam] = ACK_TMP_PREFIX;
 	static unsigned long count = 0;
 	static char* name = NULL;
 
diff --git a/lang/cem/libcc.ansi/sys/stdio/ungetc.c b/lang/cem/libcc.ansi/sys/stdio/ungetc.c
index a53cc1cf9..6097e5104 100644
--- a/lang/cem/libcc.ansi/sys/stdio/ungetc.c
+++ b/lang/cem/libcc.ansi/sys/stdio/ungetc.c
@@ -6,7 +6,7 @@
 #include <stdio.h>
 #include "loc_incl.h"
 
-#if ACKCONF_WANT_STDIO
+#if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
 int ungetc(int ch, FILE* stream)
 {
diff --git a/lang/cem/libcc.ansi/sys/stdio/vfprintf.c b/lang/cem/libcc.ansi/sys/stdio/vfprintf.c
index 02b473dd6..8f7008aae 100644
--- a/lang/cem/libcc.ansi/sys/stdio/vfprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/vfprintf.c
@@ -9,9 +9,17 @@
 
 #if ACKCONF_WANT_STDIO
 
+static FILE* vfprintf_stream;
+
+static void vfprintf_putc(int c)
+{
+	putc(c, vfprintf_stream);
+}
+
 int vfprintf(FILE* stream, const char* format, va_list arg)
 {
-	return _doprnt(format, arg, stream);
+	vfprintf_stream = stream;
+	return _doprnt(format, arg, vfprintf_putc);
 }
 
 #endif
diff --git a/lang/cem/libcc.ansi/sys/stdio/vfscanf.c b/lang/cem/libcc.ansi/sys/stdio/vfscanf.c
new file mode 100644
index 000000000..9411b65c6
--- /dev/null
+++ b/lang/cem/libcc.ansi/sys/stdio/vfscanf.c
@@ -0,0 +1,30 @@
+/*
+ * vfscanf.c - read formatted input from stream
+ */
+/* $Id$ */
+
+#include <stdio.h>
+#include <stdarg.h>
+#include "loc_incl.h"
+
+#if ACKCONF_WANT_STDIO
+
+static FILE* vfscanf_stream;
+
+static int vfscanf_getc(void)
+{
+	return getc(vfscanf_stream);
+}
+
+static void vfscanf_ungetc(int c)
+{
+	ungetc(c, vfscanf_stream);
+}
+
+int vfscanf(FILE* stream, const char* format, va_list ap)
+{
+	vfscanf_stream = stream;
+	return _doscan(format, ap, vfscanf_getc, vfscanf_ungetc);
+}
+
+#endif
diff --git a/lang/cem/libcc.ansi/sys/stdio/vprintf.c b/lang/cem/libcc.ansi/sys/stdio/vprintf.c
index 5cc6b837f..192601cc8 100644
--- a/lang/cem/libcc.ansi/sys/stdio/vprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/vprintf.c
@@ -11,7 +11,7 @@
 
 int vprintf(const char* format, va_list arg)
 {
-	return _doprnt(format, arg, stdout);
+	return vfprintf(stdout, format, arg);
 }
 
 #endif
diff --git a/lang/cem/libcc.ansi/sys/stdio/vsnprintf.c b/lang/cem/libcc.ansi/sys/stdio/vsnprintf.c
index d973b8066..94348d70c 100644
--- a/lang/cem/libcc.ansi/sys/stdio/vsnprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/vsnprintf.c
@@ -9,19 +9,26 @@
 
 #if ACKCONF_WANT_STDIO
 
-int vsnprintf(char* s, size_t len, const char* format, va_list arg)
+static char* output_buffer;
+static size_t output_buffer_len;
+
+static void snprintf_putc(int c)
+{
+	if (output_buffer_len)
+	{
+		*output_buffer++ = c;
+		output_buffer_len--;
+	}
+}
+
+int vsnprintf(char* s, size_t len, const char* format, va_list ap)
 {
 	int retval;
-	FILE tmp_stream;
 
-	tmp_stream._fd = -1;
-	tmp_stream._flags = _IOWRITE + _IONBF + _IOWRITING;
-	tmp_stream._buf = (unsigned char*)s;
-	tmp_stream._ptr = (unsigned char*)s;
-	tmp_stream._count = len;
-
-	retval = _doprnt(format, arg, &tmp_stream);
-	putc('\0', &tmp_stream);
+	output_buffer = s;
+	output_buffer_len = len;
+	retval = _doprnt(format, ap, snprintf_putc);
+	snprintf_putc('\0');
 
 	return retval;
 }
diff --git a/lang/cem/libcc.ansi/sys/stdio/vsprintf.c b/lang/cem/libcc.ansi/sys/stdio/vsprintf.c
index 00065bec0..81147591f 100644
--- a/lang/cem/libcc.ansi/sys/stdio/vsprintf.c
+++ b/lang/cem/libcc.ansi/sys/stdio/vsprintf.c
@@ -9,21 +9,9 @@
 
 #if ACKCONF_WANT_STDIO
 
-int vsprintf(char* s, const char* format, va_list arg)
+int vsprintf(char* s, const char* format, va_list ap)
 {
-	int retval;
-	FILE tmp_stream;
-
-	tmp_stream._fd = -1;
-	tmp_stream._flags = _IOWRITE + _IONBF + _IOWRITING;
-	tmp_stream._buf = (unsigned char*)s;
-	tmp_stream._ptr = (unsigned char*)s;
-	tmp_stream._count = 32767;
-
-	retval = _doprnt(format, arg, &tmp_stream);
-	putc('\0', &tmp_stream);
-
-	return retval;
+	return vsnprintf(s, 32767, format, ap);
 }
 
 #endif
diff --git a/plat/cpm/include/ack/file.h b/plat/cpm/include/ack/file.h
new file mode 100644
index 000000000..8e7393cdc
--- /dev/null
+++ b/plat/cpm/include/ack/file.h
@@ -0,0 +1,22 @@
+#ifndef ACK_FILE_H
+#define ACK_FILE_H
+
+/* CP/M custom FILE* implementation. */
+
+#define L_tmpnam 16 /* 0a:12345678.abc */
+#define ACK_TMP_PREFIX "0a:tmp"
+#define TMP_MAX 999
+
+#include <cpm.h>
+
+struct FILE
+{
+    uint8_t user;
+    FCB fcb;
+    char buffer[128];
+};
+
+#define FOPEN_MAX 8
+extern FILE* __files[FOPEN_MAX];
+
+#endif
diff --git a/plat/cpm/include/ack/plat.h b/plat/cpm/include/ack/plat.h
index 321dadf18..6e1bac6ae 100644
--- a/plat/cpm/include/ack/plat.h
+++ b/plat/cpm/include/ack/plat.h
@@ -11,4 +11,12 @@
  
 #define ACKCONF_WANT_EMULATED_TIME 0
 
+/* CP/M's underlying file abstraction is weird and doesn't map well onto
+ * file descriptors. Disable the standard FILE* mechanism in favour of our
+ * own.
+ */
+
+#define ACKCONF_WANT_EMULATED_FILE 0
+#define ACKCONF_WANT_EMULATED_POPEN 0
+
 #endif
diff --git a/plat/cpm/include/build.lua b/plat/cpm/include/build.lua
index 9820e3e09..ea35db386 100644
--- a/plat/cpm/include/build.lua
+++ b/plat/cpm/include/build.lua
@@ -9,6 +9,7 @@ local function addheader(h)
 end
 
 addheader("ack/plat.h")
+addheader("ack/file.h")
 addheader("sys/types.h")
 addheader("cpm.h")