diff --git a/boot/boot.h b/boot/boot.h
index 3b9bc6528..bdda5e242 100644
--- a/boot/boot.h
+++ b/boot/boot.h
@@ -93,7 +93,7 @@ void raw_copy(u32_t dstaddr, u32_t srcaddr, u32_t count);
 			/* Copy bytes from anywhere to anywhere. */
 u16_t get_word(u32_t addr);
 			/* Get a word from anywhere. */
-void put_word(u32_t addr, U16_t word);
+void put_word(u32_t addr, u16_t word);
 			/* Put a word anywhere. */
 void relocate(void);
 			/* Switch to a copy of this program. */
diff --git a/boot/rawfs.c b/boot/rawfs.c
index e77ca35e9..74c6bcf2b 100644
--- a/boot/rawfs.c
+++ b/boot/rawfs.c
@@ -2,7 +2,6 @@
  *								23 Dec 1991
  *					     Based on readfs by Paul Polderman
  */
-#define nil 0
 #define _POSIX_SOURCE	1
 #define _MINIX		1
 #include <sys/types.h>
diff --git a/commands/ps/ps.c b/commands/ps/ps.c
index 46dd2fe19..2fabd0631 100644
--- a/commands/ps/ps.c
+++ b/commands/ps/ps.c
@@ -178,17 +178,14 @@ struct pstat {			/* structure filled by pstat() */
 #define	R_STATE		'R'	/* Runnable */
 #define	T_STATE		'T'	/* stopped (Trace) */
 
-_PROTOTYPE(char *tname, (dev_t dev_nr ));
-_PROTOTYPE(char *taskname, (int p_nr ));
-_PROTOTYPE(char *prrecv, (struct pstat *bufp ));
 _PROTOTYPE(void disaster, (int sig ));
 _PROTOTYPE(int main, (int argc, char *argv []));
 _PROTOTYPE(char *get_args, (struct pstat *bufp ));
 _PROTOTYPE(int pstat, (int p_nr, struct pstat *bufp, int Eflag ));
 _PROTOTYPE(int addrread, (int fd, phys_clicks base, vir_bytes addr, 
 						    char *buf, int nbytes ));
-_PROTOTYPE(void usage, (char *pname ));
-_PROTOTYPE(void err, (char *s ));
+_PROTOTYPE(void usage, (const char *pname ));
+_PROTOTYPE(void err, (const char *s ));
 _PROTOTYPE(int gettynames, (void));
 
 
@@ -198,7 +195,7 @@ _PROTOTYPE(int gettynames, (void));
  * Tname assumes that the first three letters of the tty's name can be omitted
  * and returns the rest (except for the console, which yields "co").
  */
-char *tname(dev_t dev_nr)
+PRIVATE char *tname(dev_t dev_nr)
 {
   int i;
 
@@ -212,8 +209,7 @@ char *tname(dev_t dev_nr)
 }
 
 /* Return canonical task name of task p_nr; overwritten on each call (yucch) */
-char *taskname(p_nr)
-int p_nr;
+PRIVATE char *taskname(int p_nr)
 {
   int n;
   n = _ENDPOINT_P(p_nr) + nr_tasks;
@@ -226,8 +222,7 @@ int p_nr;
 /* Prrecv prints the RECV field for process with pstat buffer pointer bufp.
  * This is either "ANY", "taskname", or "(blockreason) taskname".
  */
-char *prrecv(bufp)
-struct pstat *bufp;
+PRIVATE char *prrecv(struct pstat *bufp)
 {
   char *blkstr, *task;		/* reason for blocking and task */
   static char recvstr[20];
@@ -483,10 +478,7 @@ struct pstat *bufp;
 /* Pstat collects info on process number p_nr and returns it in buf.
  * It is assumed that tasks do not have entries in fproc/mproc.
  */
-int pstat(p_nr, bufp, endpoints)
-int p_nr;
-struct pstat *bufp;
-int endpoints;
+int pstat(int p_nr, struct pstat *bufp, int endpoints)
 {
   int p_ki = p_nr + nr_tasks;	/* kernel proc index */
 
@@ -581,12 +573,7 @@ int endpoints;
 }
 
 /* Addrread reads nbytes from offset addr to click base of fd into buf. */
-int addrread(fd, base, addr, buf, nbytes)
-int fd;
-phys_clicks base;
-vir_bytes addr;
-char *buf;
-int nbytes;
+int addrread(int fd, phys_clicks base, vir_bytes addr, char *buf, int nbytes)
 {
   if (lseek(fd, ((off_t) base << CLICK_SHIFT) + addr, 0) < 0)
 	return -1;
@@ -594,15 +581,13 @@ int nbytes;
   return read(fd, buf, nbytes);
 }
 
-void usage(pname)
-char *pname;
+void usage(const char *pname)
 {
   fprintf(stderr, "Usage: %s [-][aeflx]\n", pname);
   exit(1);
 }
 
-void err(s)
-char *s;
+void err(const char *s)
 {
   extern int errno;
 
@@ -615,7 +600,7 @@ char *s;
 }
 
 /* Fill ttyinfo by fstatting character specials in /dev. */
-int gettynames()
+int gettynames(void)
 {
   static char dev_path[] = "/dev/";
   struct stat statbuf;
diff --git a/commands/simple/du.c b/commands/simple/du.c
index d0091235b..ee3e136b6 100644
--- a/commands/simple/du.c
+++ b/commands/simple/du.c
@@ -66,7 +66,7 @@ typedef struct already {
 } ALREADY;
 
 _PROTOTYPE(int main, (int argc, char **argv));
-_PROTOTYPE(int makedname, (char *d, char *f, char *out, int outlen));
+PRIVATE _PROTOTYPE(int makedname, (char *d, char *f, char *out, int outlen));
 _PROTOTYPE(int done, (dev_t dev, ino_t inum, nlink_t nlink));
 _PROTOTYPE(long dodir, (char *d, int thislev, dev_t dev));
 
@@ -86,16 +86,11 @@ int alc;
  *	directory entry, placing it in out. If this would overflow,
  *	return 0, otherwise 1.
  */
-int makedname(d, f, out, outlen)
-char *d;
-char *f;
-char *out;
-int outlen;
+PRIVATE int makedname(char *d, char *f, char *out, int outlen)
 {
   char *cp;
-  int length;
+  int length = strlen(f);
 
-  length = strlen(f);
   if (strlen(d) + length + 2 > outlen) return(0);
   for (cp = out; *d; *cp++ = *d++);
   if (*(cp - 1) != '/') *cp++ = '/';
diff --git a/commands/simple/fsck1.c b/commands/simple/fsck1.c
index b36dbb8c5..87c935ca5 100644
--- a/commands/simple/fsck1.c
+++ b/commands/simple/fsck1.c
@@ -9,7 +9,6 @@
 #define NR_ZONE_NUMS V1_NR_TZONES
 #define ZONE_NUM_SIZE V1_ZONE_NUM_SIZE
 #define bit_nr u16_t	/* perhaps bit_t should be used, although slower */
-#define Bit_nr U16_t
 #define block_nr block_t
 #define d_inode d1_inode
 #define d_inum d_ino
@@ -19,7 +18,6 @@
 #define i_size d1_size
 #define i_zone d1_zone
 #define zone_nr zone1_t
-#define Zone_nr Zone1_t
 
 /* fsck - file system checker		Author: Robbert van Renesse */
 
@@ -138,22 +136,22 @@ char answer[] = "Answer questions with y or n.  Then hit RETURN";
 
 _PROTOTYPE(int main, (int argc, char **argv));
 _PROTOTYPE(void initvars, (void));
-_PROTOTYPE(void fatal, (char *s));
+_PROTOTYPE(void fatal, (const char *s));
 _PROTOTYPE(int eoln, (int c));
-_PROTOTYPE(int yes, (char *question));
-_PROTOTYPE(int atoo, (char *s));
+PRIVATE _PROTOTYPE(int yes, (const char *question));
+PRIVATE _PROTOTYPE(int atoo, (const char *s));
 _PROTOTYPE(int input, (char *buf, int size));
-_PROTOTYPE(char *alloc, (unsigned nelem, unsigned elsize));
-_PROTOTYPE(void printname, (char *s));
+PRIVATE _PROTOTYPE(char *alloc, (unsigned nelem, unsigned elsize));
+PRIVATE _PROTOTYPE(void printname, (const char *s));
 _PROTOTYPE(void printrec, (struct stack *sp));
 _PROTOTYPE(void printpath, (int mode, int nlcr));
 _PROTOTYPE(void devopen, (void));
 _PROTOTYPE(void devclose, (void));
 _PROTOTYPE(void devio, (block_nr bno, int dir));
 _PROTOTYPE(void devread, (long offset, char *buf, int size));
-_PROTOTYPE(void devwrite, (long offset, char *buf, int size));
-_PROTOTYPE(void pr, (char *fmt, int cnt, char *s, char *p));
-_PROTOTYPE(bit_nr getnumber, (char *s));
+PRIVATE _PROTOTYPE(void devwrite, (long offset, const char *buf, int size));
+_PROTOTYPE(void pr, (const char *fmt, int cnt, const char *s, const char *p));
+_PROTOTYPE(bit_nr getnumber, (const char *s));
 _PROTOTYPE(char **getlist, (char ***argv, char *type));
 _PROTOTYPE(void lsuper, (void));
 _PROTOTYPE(void getsuper, (void));
@@ -162,12 +160,12 @@ _PROTOTYPE(void lsi, (char **clist));
 _PROTOTYPE(bitchunk_t *allocbitmap, (int nblk));
 _PROTOTYPE(void loadbitmap, (bitchunk_t *bitmap, block_nr bno, int nblk));
 _PROTOTYPE(void dumpbitmap, (bitchunk_t *bitmap, block_nr bno, int nblk));
-_PROTOTYPE(void fillbitmap, (bitchunk_t *bitmap, Bit_nr lwb, Bit_nr upb, char **list));
+_PROTOTYPE(void fillbitmap, (bitchunk_t *bitmap, bit_nr lwb, bit_nr upb, char **list));
 _PROTOTYPE(void freebitmap, (bitchunk_t *p));
 _PROTOTYPE(void getbitmaps, (void));
 _PROTOTYPE(void putbitmaps, (void));
-_PROTOTYPE(void chkword, (unsigned w1, unsigned w2, Bit_nr bit, char *type, int *n, int *report));
-_PROTOTYPE(void chkmap, (bitchunk_t *cmap, bitchunk_t *dmap, Bit_nr bit, block_nr blkno, int nblk, char *type));
+_PROTOTYPE(void chkword, (unsigned w1, unsigned w2, bit_nr bit, char *type, int *n, int *report));
+_PROTOTYPE(void chkmap, (bitchunk_t *cmap, bitchunk_t *dmap, bit_nr bit, block_nr blkno, int nblk, char *type));
 _PROTOTYPE(void chkilist, (void));
 _PROTOTYPE(void getcount, (void));
 _PROTOTYPE(void counterror, (Ino_t ino));
@@ -180,12 +178,12 @@ _PROTOTYPE(void make_printable_name, (char *dst, char *src, int n));
 _PROTOTYPE(int chkdots, (Ino_t ino, off_t pos, dir_struct *dp, Ino_t exp));
 _PROTOTYPE(int chkname, (Ino_t ino, dir_struct *dp));
 _PROTOTYPE(int chkentry, (Ino_t ino, off_t pos, dir_struct *dp));
-_PROTOTYPE(int chkdirzone, (Ino_t ino, d_inode *ip, off_t pos, Zone_nr zno));
-_PROTOTYPE(void errzone, (char *mess, Zone_nr zno, int level, off_t pos));
-_PROTOTYPE(int markzone, (Ino_t ino, Zone_nr zno, int level, off_t pos));
-_PROTOTYPE(int chkindzone, (Ino_t ino, d_inode *ip, off_t *pos, Zone_nr zno, int level));
+_PROTOTYPE(int chkdirzone, (Ino_t ino, d_inode *ip, off_t pos, zone_nr zno));
+_PROTOTYPE(void errzone, (const char *mess, zone_nr zno, int level, off_t pos));
+_PROTOTYPE(int markzone, (Ino_t ino, zone_nr zno, int level, off_t pos));
+_PROTOTYPE(int chkindzone, (Ino_t ino, d_inode *ip, off_t *pos, zone_nr zno, int level));
 _PROTOTYPE(off_t jump, (int level));
-_PROTOTYPE(int zonechk, (Ino_t ino, d_inode *ip, off_t *pos, Zone_nr zno, int level));
+_PROTOTYPE(int zonechk, (Ino_t ino, d_inode *ip, off_t *pos, zone_nr zno, int level));
 _PROTOTYPE(int chkzones, (Ino_t ino, d_inode *ip, off_t *pos, zone_nr *zlist, int len, int level));
 _PROTOTYPE(int chkfile, (Ino_t ino, d_inode *ip));
 _PROTOTYPE(int chkdirectory, (Ino_t ino, d_inode *ip));
@@ -212,25 +210,22 @@ void initvars()
 }
 
 /* Print the string `s' and exit. */
-void fatal(s)
-char *s;
+void fatal(const char *s)
 {
   printf("%s\nfatal\n", s);
   exit(-1);
 }
 
 /* Test for end of line. */
-int eoln(c)
-int c;
+int eoln(int c)
 {
   return(c == EOF || c == '\n' || c == '\r');
 }
 
 /* Ask a question and get the answer unless automatic is set. */
-int yes(question)
-char *question;
+PRIVATE int yes(const char *question)
 {
-  register c, answer;
+  int c, answer;
 
   if (!repair) {
 	printf("\n");
@@ -248,8 +243,7 @@ char *question;
 }
 
 /* Convert string to integer.  Representation is octal. */
-int atoo(s)
-register char *s;
+PRIVATE int atoo(const char *s)
 {
   register int n = 0;
 
@@ -261,9 +255,7 @@ register char *s;
 }
 
 /* If repairing the file system, print a prompt and get a string from user. */
-int input(buf, size)
-char *buf;
-int size;
+int input(char *buf, int size)
 {
   register char *p = buf;
 
@@ -287,8 +279,7 @@ int size;
 }
 
 /* Allocate some memory and zero it. */
-char *alloc(nelem, elsize)
-unsigned nelem, elsize;
+PRIVATE char *alloc(unsigned nelem, unsigned elsize)
 {
   char *p;
 
@@ -298,8 +289,7 @@ unsigned nelem, elsize;
 }
 
 /* Print the name in a directory entry. */
-void printname(s)
-char *s;
+PRIVATE void printname(const char *s)
 {
   register n = NAME_MAX;
   int c;
@@ -315,8 +305,7 @@ char *s;
 /* Print the pathname given by a linked list pointed to by `sp'.  The
  * names are in reverse order.
  */
-void printrec(sp)
-struct stack *sp;
+void printrec(struct stack *sp)
 {
   if (sp->st_next != 0) {
 	printrec(sp->st_next);
@@ -326,9 +315,7 @@ struct stack *sp;
 }
 
 /* Print the current pathname.  */
-void printpath(mode, nlcr)
-int mode;
-int nlcr;
+void printpath(int mode, int nlcr)
 {
   if (ftop->st_next == 0)
 	putchar('/');
@@ -346,7 +333,7 @@ int nlcr;
 }
 
 /* Open the device.  */
-void devopen()
+void devopen(void)
 {
   if ((dev = open(device, repair ? O_RDWR : O_RDONLY)) < 0) {
 	perror(device);
@@ -364,9 +351,7 @@ void devclose()
 }
 
 /* Read or write a block. */
-void devio(bno, dir)
-block_nr bno;
-int dir;
+void devio(block_nr bno, int dir)
 {
   if (dir == READING && bno == thisblk) return;
   thisblk = bno;
@@ -391,20 +376,14 @@ int dir;
 }
 
 /* Read `size' bytes from the disk starting at byte `offset'. */
-void devread(offset, buf, size)
-long offset;
-char *buf;
-int size;
+void devread(long offset, char *buf, int size)
 {
   devio((block_nr) (offset / BLOCK_SIZE), READING);
   memmove(buf, &rwbuf[(int) (offset % BLOCK_SIZE)], (size_t)size);
 }
 
 /* Write `size' bytes to the disk starting at byte `offset'. */
-void devwrite(offset, buf, size)
-long offset;
-char *buf;
-int size;
+static void devwrite(long offset, const char *buf, int size)
 {
   if (!repair) fatal("internal error (devwrite)");
   if (size != BLOCK_SIZE) devio((block_nr) (offset / BLOCK_SIZE), READING);
@@ -414,16 +393,13 @@ int size;
 }
 
 /* Print a string with either a singular or a plural pronoun. */
-void pr(fmt, cnt, s, p)
-char *fmt, *s, *p;
-int cnt;
+void pr(const char *fmt, int cnt, const char *s, const char *p)
 {
   printf(fmt, cnt, cnt == 1 ? s : p);
 }
 
 /* Convert string to number. */
-bit_nr getnumber(s)
-register char *s;
+bit_nr getnumber(const char *s)
 {
   register bit_nr n = 0;
 
@@ -435,8 +411,7 @@ register char *s;
 }
 
 /* See if the list pointed to by `argv' contains numbers. */
-char **getlist(argv, type)
-char ***argv, *type;
+char **getlist(char ***argv, char *type)
 {
   register char **list = *argv;
   register empty = 1;
@@ -455,7 +430,7 @@ char ***argv, *type;
 /* Make a listing of the super block.  If `repair' is set, ask the user
  * for changes.
  */
-void lsuper()
+void lsuper(void)
 {
   char buf[80];
 
@@ -483,7 +458,7 @@ void lsuper()
 }
 
 /* Get the super block from either disk or user.  Do some initial checks. */
-void getsuper()
+void getsuper(void)
 {
   devread(btoa(BLK_SUPER), (char *) &sb, sizeof(sb));
   if (listsuper) lsuper();
@@ -499,7 +474,7 @@ void getsuper()
 }
 
 /* Check the super block for reasonable contents. */
-void chksuper()
+void chksuper(void)
 {
   register n;
   register off_t maxsize;
@@ -541,8 +516,7 @@ void chksuper()
 /* Make a listing of the inodes given by `clist'.  If `repair' is set, ask
  * the user for changes.
  */
-void lsi(clist)
-char **clist;
+void lsi(char **clist)
 {
   register bit_nr bit;
   register ino_t ino;
@@ -571,8 +545,7 @@ char **clist;
 }
 
 /* Allocate `nblk' blocks worth of bitmap. */
-bitchunk_t *allocbitmap(nblk)
-int nblk;
+bitchunk_t *allocbitmap(int nblk)
 {
   register bitchunk_t *bitmap;
 
@@ -582,10 +555,7 @@ int nblk;
 }
 
 /* Load the bitmap starting at block `bno' from disk. */
-void loadbitmap(bitmap, bno, nblk)
-bitchunk_t *bitmap;
-block_nr bno;
-int nblk;
+void loadbitmap(bitchunk_t *bitmap, block_nr bno, int nblk)
 {
   register i;
   register bitchunk_t *p;
@@ -597,10 +567,7 @@ int nblk;
 }
 
 /* Write the bitmap starting at block `bno' to disk. */
-void dumpbitmap(bitmap, bno, nblk)
-bitchunk_t *bitmap;
-block_nr bno;
-int nblk;
+void dumpbitmap(bitchunk_t *bitmap, block_nr bno, int nblk)
 {
   register i;
   register bitchunk_t *p = bitmap;
@@ -610,10 +577,7 @@ int nblk;
 }
 
 /* Set the bits given by `list' in the bitmap. */
-void fillbitmap(bitmap, lwb, upb, list)
-bitchunk_t *bitmap;
-bit_nr lwb, upb;
-char **list;
+void fillbitmap(bitchunk_t *bitmap, bit_nr lwb, bit_nr upb, char **list)
 {
   register bit_nr bit;
 
@@ -659,11 +623,8 @@ void putbitmaps()
 /* `w1' and `w2' are differing words from two bitmaps that should be
  * identical.  Print what's the matter with them.
  */
-void chkword(w1, w2, bit, type, n, report)
-unsigned w1, w2;
-char *type;
-bit_nr bit;
-int *n, *report;
+void chkword(unsigned w1, unsigned w2, bit_nr bit, char *type,
+    int *n, int *report)
 {
   for (; (w1 | w2); w1 >>= 1, w2 >>= 1, bit++)
 	if ((w1 ^ w2) & 1 && ++(*n) % MAXPRINT == 0 && *report &&
@@ -679,12 +640,8 @@ int *n, *report;
 /* Check if the given (correct) bitmap is identical with the one that is
  * on the disk.  If not, ask if the disk should be repaired.
  */
-void chkmap(cmap, dmap, bit, blkno, nblk, type)
-bitchunk_t *cmap, *dmap;
-bit_nr bit;
-block_nr blkno;
-int nblk;
-char *type;
+void chkmap(bitchunk_t *cmap, bitchunk_t *dmap, bit_nr bit,
+    block_nr blkno, int nblk, char *type)
 {
   register bitchunk_t *p = dmap, *q = cmap;
   int report = 1, nerr = 0;
@@ -706,7 +663,7 @@ char *type;
 }
 
 /* See if the inodes that aren't allocated are cleared. */
-void chkilist()
+void chkilist(void)
 {
   register ino_t ino = 1;
   mode_t mode;
@@ -732,8 +689,7 @@ void getcount()
 }
 
 /* The reference count for inode `ino' is wrong.  Ask if it should be adjusted. */
-void counterror(ino)
-ino_t ino;
+void counterror(ino_t ino)
 {
   d_inode inode;
 
@@ -799,9 +755,7 @@ void printperm(mode_t mode, int shift, int special, int overlay)
 }
 
 /* List the given inode. */
-void list(ino, ip)
-ino_t ino;
-d_inode *ip;
+void list(ino_t ino, d_inode *ip)
 {
   if (firstlist) {
 	firstlist = 0;
@@ -838,8 +792,7 @@ d_inode *ip;
  * Don't name the function remove() - that is owned by ANSI, and chaos results
  * when it is a macro.
  */
-int Remove(dp)
-dir_struct *dp;
+int Remove(dir_struct *dp)
 {
   setbit(spec_imap, (bit_nr) dp->d_inum);
   if (yes(". remove entry")) {
@@ -887,10 +840,7 @@ register int n;
 }
 
 /* See if the `.' or `..' entry is as expected. */
-int chkdots(ino, pos, dp, exp)
-ino_t ino, exp;
-off_t pos;
-dir_struct *dp;
+int chkdots(ino_t ino, off_t pos, dir_struct *dp, ino_t exp)
 {
   char printable_name[4 * NAME_MAX + 1];
 
@@ -922,9 +872,7 @@ dir_struct *dp;
 }
 
 /* Check the name in a directory entry. */
-int chkname(ino, dp)
-ino_t ino;
-dir_struct *dp;
+int chkname(ino_t ino, dir_struct *dp)
 {
   register n = NAME_MAX + 1;
   register char *p = dp->d_name;
@@ -952,10 +900,7 @@ dir_struct *dp;
 /* Check a directory entry.  Here the routine `descendtree' is called
  * recursively to check the file or directory pointed to by the entry.
  */
-int chkentry(ino, pos, dp)
-ino_t ino;
-off_t pos;
-dir_struct *dp;
+int chkentry(ino_t ino, off_t pos, dir_struct *dp)
 {
   if (dp->d_inum < ROOT_INODE || dp->d_inum > sb.s_ninodes) {
 	printf("bad inode found in directory ");
@@ -1003,11 +948,7 @@ dir_struct *dp;
 /* Check a zone of a directory by checking all the entries in the zone.
  * The zone is split up into chunks to not allocate too much stack.
  */
-int chkdirzone(ino, ip, pos, zno)
-ino_t ino;
-d_inode *ip;
-off_t pos;
-zone_nr zno;
+int chkdirzone(ino_t ino, d_inode *ip, off_t pos, zone_nr zno)
 {
   dir_struct dirblk[CDIRECT];
   register dir_struct *dp;
@@ -1041,11 +982,7 @@ zone_nr zno;
 }
 
 /* There is something wrong with the given zone.  Print some details. */
-void errzone(mess, zno, level, pos)
-char *mess;
-zone_nr zno;
-int level;
-off_t pos;
+void errzone(const char *mess, zone_nr zno, int level, off_t pos)
 {
   printf("%s zone in ", mess);
   printpath(1, 0);
@@ -1062,11 +999,7 @@ off_t pos;
 /* Found the given zone in the given inode.  Check it, and if ok, mark it
  * in the zone bitmap.
  */
-int markzone(ino, zno, level, pos)
-ino_t ino;
-zone_nr zno;
-int level;
-off_t pos;
+int markzone(ino_t ino, zone_nr zno, int level, off_t pos)
 {
   register bit_nr bit = (bit_nr) zno - FIRST + 1;
 
@@ -1089,12 +1022,7 @@ off_t pos;
 /* Check an indirect zone by checking all of its entries.
  * The zone is split up into chunks to not allocate too much stack.
  */
-int chkindzone(ino, ip, pos, zno, level)
-ino_t ino;
-d_inode *ip;
-off_t *pos;
-zone_nr zno;
-int level;
+int chkindzone(ino_t ino, d_inode *ip, off_t *pos, zone_nr zno, int level)
 {
   zone_nr indirect[CINDIR];
   register n = NR_INDIRECTS / CINDIR;
@@ -1111,8 +1039,7 @@ int level;
 /* Return the size of a gap in the file, represented by a null zone number
  * at some level of indirection.
  */
-off_t jump(level)
-int level;
+off_t jump(int level)
 {
   off_t power = ZONE_SIZE;
 
@@ -1125,12 +1052,7 @@ int level;
 /* Check a zone, which may be either a normal data zone, a directory zone,
  * or an indirect zone.
  */
-int zonechk(ino, ip, pos, zno, level)
-ino_t ino;
-d_inode *ip;
-off_t *pos;
-zone_nr zno;
-int level;
+int zonechk(ino_t ino, d_inode *ip, off_t *pos, zone_nr zno, int level)
 {
   if (level == 0) {
 	if ((ip->i_mode & I_TYPE) == I_DIRECTORY &&
@@ -1143,13 +1065,8 @@ int level;
 }
 
 /* Check a list of zones given by `zlist'. */
-int chkzones(ino, ip, pos, zlist, len, level)
-ino_t ino;
-d_inode *ip;
-off_t *pos;
-zone_nr *zlist;
-int len;
-int level;
+int chkzones(ino_t ino, d_inode *ip, off_t *pos, zone_nr *zlist,
+ int len, int level)
 {
   register ok = 1, i;
 
@@ -1183,9 +1100,7 @@ d_inode *ip;
 }
 
 /* Check a directory by checking the contents.  Check if . and .. are present. */
-int chkdirectory(ino, ip)
-ino_t ino;
-d_inode *ip;
+int chkdirectory(ino_t ino, d_inode *ip)
 {
   register ok;
 
@@ -1207,9 +1122,7 @@ d_inode *ip;
 #ifdef I_SYMBOLIC_LINK
 
 /* Check the validity of a symbolic link. */
-int chklink(ino, ip)
-ino_t ino;
-d_inode *ip;
+int chklink(ino_t ino, d_inode *ip)
 {
   int ok;
 
@@ -1255,9 +1168,7 @@ d_inode *ip;
 }
 
 /* Check the mode and contents of an inode. */
-int chkmode(ino, ip)
-ino_t ino;
-d_inode *ip;
+int chkmode(ino_t ino, d_inode *ip)
 {
   switch (ip->i_mode & I_TYPE) {
       case I_REGULAR:
@@ -1290,9 +1201,7 @@ d_inode *ip;
 }
 
 /* Check an inode. */
-int chkinode(ino, ip)
-ino_t ino;
-d_inode *ip;
+int chkinode(ino_t ino, d_inode *ip)
 {
   if (ino == ROOT_INODE && (ip->i_mode & I_TYPE) != I_DIRECTORY) {
 	printf("root inode is not a directory ");
diff --git a/commands/talk/net.c b/commands/talk/net.c
index 6dd6beb24..eee4acfc5 100644
--- a/commands/talk/net.c
+++ b/commands/talk/net.c
@@ -195,17 +195,15 @@ udp_io_hdr_t *udp_io_hdr;
    return(0);
 }
 
-void TimeOut(sig)
-int sig;
+void TimeOut(int sig)
 {
 }
 
-int NetConnect(port)
-u16_t port;
+int NetConnect(u16_t port)
 {
-int s;
-nwio_tcpconf_t tcpconf;
-nwio_tcpcl_t tcpcopt;
+   int s;
+   nwio_tcpconf_t tcpconf;
+   nwio_tcpcl_t tcpcopt;
 
    tcpconf.nwtc_flags = NWTC_NOFLAGS;
    tcpconf.nwtc_flags |= NWTC_LP_SET | NWTC_SET_RA | NWTC_SET_RP;
diff --git a/commands/talk/net.h b/commands/talk/net.h
index 56358763f..8d7d725be 100644
--- a/commands/talk/net.h
+++ b/commands/talk/net.h
@@ -11,5 +11,5 @@ extern int tcp_fd;
 _PROTOTYPE(int NetInit, (void));
 _PROTOTYPE(int getreply, (struct talk_reply *reply, int timeout));
 _PROTOTYPE(int sendrequest, (struct talk_request *request, int here));
-_PROTOTYPE(int NetConnect, (U16_t port));
+_PROTOTYPE(int NetConnect, (u16_t port));
 _PROTOTYPE(int NetListen, (int timeout));
diff --git a/drivers/audio/es1370/pci_helper.c b/drivers/audio/es1370/pci_helper.c
index 64362ca9a..6cea93c1e 100644
--- a/drivers/audio/es1370/pci_helper.c
+++ b/drivers/audio/es1370/pci_helper.c
@@ -33,7 +33,7 @@ PUBLIC unsigned pci_inw(u16_t port) {
 
 
 PUBLIC unsigned pci_inl(u16_t port) {
-	U32_t value;
+	u32_t value;
 	int s;
 	if ((s=sys_inl(port, &value)) !=OK)
 		printf("%s: warning, sys_inl failed: %d\n", DRIVER_NAME, s);
diff --git a/drivers/dp8390/rtl8029.c b/drivers/dp8390/rtl8029.c
index e5885abc1..d2ff930ec 100644
--- a/drivers/dp8390/rtl8029.c
+++ b/drivers/dp8390/rtl8029.c
@@ -38,7 +38,7 @@ _PROTOTYPE( static void rtl_init, (struct dpeth *dep)			);
 #if 0
 _PROTOTYPE( static u16_t get_ee_word, (dpeth_t *dep, int a)		);
 _PROTOTYPE( static void ee_wen, (dpeth_t *dep)				);
-_PROTOTYPE( static void set_ee_word, (dpeth_t *dep, int a, U16_t w)	);
+_PROTOTYPE( static void set_ee_word, (dpeth_t *dep, int a, u16_t w)	);
 _PROTOTYPE( static void ee_wds, (dpeth_t *dep)				);
 #endif
 
diff --git a/drivers/fxp/mii.c b/drivers/fxp/mii.c
index b72765054..46a2712d0 100644
--- a/drivers/fxp/mii.c
+++ b/drivers/fxp/mii.c
@@ -16,9 +16,7 @@ Media Independent (Ethernet) Interface functions
 /*===========================================================================*
  *				mii_print_stat_speed			     *
  *===========================================================================*/
-PUBLIC void mii_print_stat_speed(stat, extstat)
-u16_t stat;
-u16_t extstat;
+PUBLIC void mii_print_stat_speed(u16_t stat, u16_t extstat)
 {
 	int fs, ft;
 
@@ -119,8 +117,7 @@ u16_t extstat;
 /*===========================================================================*
  *				mii_print_techab			     *
  *===========================================================================*/
-PUBLIC void mii_print_techab(techab)
-u16_t techab;
+PUBLIC void mii_print_techab(u16_t techab)
 {
 	int fs, ft;
 
diff --git a/drivers/fxp/mii.h b/drivers/fxp/mii.h
index ebd3b5f19..24431d2d9 100644
--- a/drivers/fxp/mii.h
+++ b/drivers/fxp/mii.h
@@ -111,8 +111,8 @@ Definitions for the Media Independent (Ethernet) Interface
 #define		MII_ESTAT_RES		0x0FFF	/* Reserved */
 /* 0x10 ... 0x1F */		/* Vendor Specific */
 
-_PROTOTYPE( void mii_print_stat_speed, (U16_t stat, U16_t extstat)	);
-_PROTOTYPE( void mii_print_techab, (U16_t techab)			);
+_PROTOTYPE( void mii_print_stat_speed, (u16_t stat, u16_t extstat)	);
+_PROTOTYPE( void mii_print_techab, (u16_t techab)			);
 
 #endif
 /*
diff --git a/drivers/rtl8139/rtl8139.c b/drivers/rtl8139/rtl8139.c
index 9da970e26..6ae4bc4dd 100644
--- a/drivers/rtl8139/rtl8139.c
+++ b/drivers/rtl8139/rtl8139.c
@@ -94,25 +94,22 @@ PUBLIC re_t re_table[RE_PORT_NR];
 static u16_t eth_ign_proto;
 static tmra_ut rl_watchdog;
 
-FORWARD _PROTOTYPE( unsigned my_inb, (U16_t port) );
-FORWARD _PROTOTYPE( unsigned my_inw, (U16_t port) );
-FORWARD _PROTOTYPE( unsigned my_inl, (U16_t port) );
-static unsigned my_inb(U16_t port) {
+static unsigned my_inb(u16_t port) {
 	u32_t value;
 	int s;
 	if ((s=sys_inb(port, &value)) !=OK)
 		printf("RTL8139: warning, sys_inb failed: %d\n", s);
 	return value;
 }
-static unsigned my_inw(U16_t port) {
+static unsigned my_inw(u16_t port) {
 	u32_t value;
 	int s;
 	if ((s=sys_inw(port, &value)) !=OK)
 		printf("RTL8139: warning, sys_inw failed: %d\n", s);
 	return value;
 }
-static unsigned my_inl(U16_t port) {
-	U32_t value;
+static unsigned my_inl(u16_t port) {
+	u32_t value;
 	int s;
 	if ((s=sys_inl(port, &value)) !=OK)
 		printf("RTL8139: warning, sys_inl failed: %d\n", s);
@@ -122,17 +119,17 @@ static unsigned my_inl(U16_t port) {
 #define rl_inw(port, offset)	(my_inw((port) + (offset)))
 #define rl_inl(port, offset)	(my_inl((port) + (offset)))
 
-static void my_outb(U16_t port, u8_t value) {
+static void my_outb(u16_t port, u8_t value) {
 	int s;
 	if ((s=sys_outb(port, value)) !=OK)
 		printf("RTL8139: warning, sys_outb failed: %d\n", s);
 }
-static void my_outw(U16_t port, U16_t value) {
+static void my_outw(u16_t port, u16_t value) {
 	int s;
 	if ((s=sys_outw(port, value)) !=OK)
 		printf("RTL8139: warning, sys_outw failed: %d\n", s);
 }
-static void my_outl(U16_t port, U32_t value) {
+static void my_outl(u16_t port, u32_t value) {
 	int s;
 	if ((s=sys_outl(port, value)) !=OK)
 		printf("RTL8139: warning, sys_outl failed: %d\n", s);
@@ -158,9 +155,9 @@ _PROTOTYPE( static void rl_writev, (const message *mp, int from_int,
 _PROTOTYPE( static void rl_writev_s, (const message *mp, int from_int)	);
 _PROTOTYPE( static void rl_check_ints, (re_t *rep)			);
 _PROTOTYPE( static void rl_report_link, (re_t *rep)			);
-_PROTOTYPE( static void mii_print_techab, (U16_t techab)		);
-_PROTOTYPE( static void mii_print_stat_speed, (U16_t stat,
-							U16_t extstat)	);
+_PROTOTYPE( static void mii_print_techab, (u16_t techab)		);
+_PROTOTYPE( static void mii_print_stat_speed, (u16_t stat,
+							u16_t extstat)	);
 _PROTOTYPE( static void rl_clear_rx, (re_t *rep)			);
 _PROTOTYPE( static void rl_do_reset, (re_t *rep)			);
 _PROTOTYPE( static void rl_getstat, (message *mp)			);
@@ -1918,8 +1915,7 @@ resspeed:
 
 }
 
-static void mii_print_techab(techab)
-u16_t techab;
+static void mii_print_techab(u16_t techab)
 {
 	int fs, ft;
 	if ((techab & MII_ANA_SEL_M) != MII_ANA_SEL_802_3)
@@ -1991,9 +1987,7 @@ u16_t techab;
 	}
 }
 
-static void mii_print_stat_speed(stat, extstat)
-u16_t stat;
-u16_t extstat;
+static void mii_print_stat_speed(u16_t stat, u16_t extstat)
 {
 	int fs, ft;
 	fs= 1;
@@ -2093,8 +2087,7 @@ u16_t extstat;
 /*===========================================================================*
  *				rl_clear_rx				     *
  *===========================================================================*/
-static void rl_clear_rx(rep)
-re_t *rep;
+static void rl_clear_rx(re_t *rep)
 {
 	port_t port;
 	u8_t cr;
@@ -2726,7 +2719,7 @@ timer_t *tp;
 _PROTOTYPE( static void rtl_init, (struct dpeth *dep)			);
 _PROTOTYPE( static u16_t get_ee_word, (dpeth_t *dep, int a)		);
 _PROTOTYPE( static void ee_wen, (dpeth_t *dep)				);
-_PROTOTYPE( static void set_ee_word, (dpeth_t *dep, int a, U16_t w)	);
+_PROTOTYPE( static void set_ee_word, (dpeth_t *dep, int a, u16_t w)	);
 _PROTOTYPE( static void ee_wds, (dpeth_t *dep)				);
 
 static void rtl_init(dep)
@@ -2882,7 +2875,7 @@ dpeth_t *dep;
 	/* micro_delay(1); */			/* Is this required? */
 }
 
-static void set_ee_word(dep, a, w)
+static void set_ee_word(dpeth_t *dep, int a, u16_t w)
 dpeth_t *dep;
 int a;
 u16_t w;
diff --git a/drivers/rtl8169/rtl8169.c b/drivers/rtl8169/rtl8169.c
index a21298189..0676428d4 100644
--- a/drivers/rtl8169/rtl8169.c
+++ b/drivers/rtl8169/rtl8169.c
@@ -182,10 +182,7 @@ static re_t re_table[RE_PORT_NR];
 static u16_t eth_ign_proto;
 static timer_t rl_watchdog;
 
-FORWARD _PROTOTYPE(unsigned my_inb, (U16_t port));
-FORWARD _PROTOTYPE(unsigned my_inw, (U16_t port));
-FORWARD _PROTOTYPE(unsigned my_inl, (U16_t port));
-static unsigned my_inb(U16_t port)
+static unsigned my_inb(u16_t port)
 {
 	u32_t value;
 	int s;
@@ -193,7 +190,7 @@ static unsigned my_inb(U16_t port)
 		printf("RTL8169: warning, sys_inb failed: %d\n", s);
 	return value;
 }
-static unsigned my_inw(U16_t port)
+static unsigned my_inw(u16_t port)
 {
 	u32_t value;
 	int s;
@@ -201,9 +198,9 @@ static unsigned my_inw(U16_t port)
 		printf("RTL8169: warning, sys_inw failed: %d\n", s);
 	return value;
 }
-static unsigned my_inl(U16_t port)
+static unsigned my_inl(u16_t port)
 {
-	U32_t value;
+	u32_t value;
 	int s;
 	if ((s = sys_inl(port, &value)) != OK)
 		printf("RTL8169: warning, sys_inl failed: %d\n", s);
@@ -213,21 +210,21 @@ static unsigned my_inl(U16_t port)
 #define rl_inw(port, offset)	(my_inw((port) + (offset)))
 #define rl_inl(port, offset)	(my_inl((port) + (offset)))
 
-static void my_outb(U16_t port, u8_t value)
+static void my_outb(u16_t port, u8_t value)
 {
 	int s;
 
 	if ((s = sys_outb(port, value)) != OK)
 		printf("RTL8169: warning, sys_outb failed: %d\n", s);
 }
-static void my_outw(U16_t port, U16_t value)
+static void my_outw(u16_t port, u16_t value)
 {
 	int s;
 
 	if ((s = sys_outw(port, value)) != OK)
 		printf("RTL8169: warning, sys_outw failed: %d\n", s);
 }
-static void my_outl(U16_t port, U32_t value)
+static void my_outl(u16_t port, u32_t value)
 {
 	int s;
 
@@ -410,7 +407,7 @@ PRIVATE void sef_cb_signal_handler(int signo)
 	exit(0);
 }
 
-static void mdio_write(U16_t port, int regaddr, int value)
+static void mdio_write(u16_t port, int regaddr, int value)
 {
 	int i;
 
@@ -428,7 +425,7 @@ static void mdio_write(U16_t port, int regaddr, int value)
 	}
 }
 
-static int mdio_read(U16_t port, int regaddr)
+static int mdio_read(u16_t port, int regaddr)
 {
 	int i, value = -1;
 
diff --git a/include/minix/devio.h b/include/minix/devio.h
index dc3d7ea7f..f654a0ae1 100644
--- a/include/minix/devio.h
+++ b/include/minix/devio.h
@@ -13,7 +13,6 @@
 #include <minix/types.h>        /* u8_t, u16_t, u32_t needed */
 
 typedef u16_t port_t;
-typedef U16_t Port_t;
 
 /* We have different granularities of port I/O: 8, 16, 32 bits.
  * Also see <ibm/portio.h>, which has functions for bytes, words,  
diff --git a/include/minix/portio.h b/include/minix/portio.h
index 852a7160e..c5aa3d68f 100644
--- a/include/minix/portio.h
+++ b/include/minix/portio.h
@@ -11,18 +11,18 @@ Created:	Jan 15, 1992 by Philip Homburg
 #include <minix/types.h>
 #endif
 
-unsigned inb(U16_t _port);
-unsigned inw(U16_t _port);
-unsigned inl(U32_t _port);
-void outb(U16_t _port, u8_t _value);
-void outw(U16_t _port, U16_t _value);
-void outl(U16_t _port, U32_t _value);
-void insb(U16_t _port, void *_buf, size_t _count);
-void insw(U16_t _port, void *_buf, size_t _count);
-void insl(U16_t _port, void *_buf, size_t _count);
-void outsb(U16_t _port, void *_buf, size_t _count);
-void outsw(U16_t _port, void *_buf, size_t _count);
-void outsl(U16_t _port, void *_buf, size_t _count);
+unsigned inb(u16_t _port);
+unsigned inw(u16_t _port);
+unsigned inl(u32_t _port);
+void outb(u16_t _port, u8_t _value);
+void outw(u16_t _port, u16_t _value);
+void outl(u16_t _port, u32_t _value);
+void insb(u16_t _port, void *_buf, size_t _count);
+void insw(u16_t _port, void *_buf, size_t _count);
+void insl(u16_t _port, void *_buf, size_t _count);
+void outsb(u16_t _port, void *_buf, size_t _count);
+void outsw(u16_t _port, void *_buf, size_t _count);
+void outsl(u16_t _port, void *_buf, size_t _count);
 void intr_disable(void);
 void intr_enable(void);
 
diff --git a/include/minix/types.h b/include/minix/types.h
index e84537222..8740ae0d0 100644
--- a/include/minix/types.h
+++ b/include/minix/types.h
@@ -101,33 +101,6 @@ typedef long	       off_t;	   /* offset within a file */
 typedef int            pid_t;	   /* process id (must be signed) */
 typedef short          uid_t;	   /* user id */
 
-/* The following types are needed because MINIX uses K&R style function
- * definitions (for maximum portability).  When a short, such as dev_t, is
- * passed to a function with a K&R definition, the compiler automatically
- * promotes it to an int.  The prototype must contain an int as the parameter,
- * not a short, because an int is what an old-style function definition
- * expects.  Thus using dev_t in a prototype would be incorrect.  It would be
- * sufficient to just use int instead of dev_t in the prototypes, but Dev_t
- * is clearer.
- */
-typedef unsigned long  U32_t;
-typedef int            I16_t;
-typedef long           I32_t;
-
-#if _EM_WSIZE == 2
-/*typedef unsigned int      Ino_t; Ino_t is now 32 bits */
-typedef unsigned int    Zone1_t;
-typedef unsigned int Bitchunk_t;
-typedef unsigned int      U16_t;
-
-#else /* _EM_WSIZE == 4, or _EM_WSIZE undefined */
-/*typedef int	          Ino_t; Ino_t is now 32 bits */
-typedef int 	        Zone1_t;
-typedef int	     Bitchunk_t;
-typedef int	          U16_t;
-
-#endif /* _EM_WSIZE == 2, etc */
-
 /* Signal handler type, e.g. SIG_IGN */
 typedef void _PROTOTYPE( (*sighandler_t), (int) );
 
diff --git a/include/net/gen/ether.h b/include/net/gen/ether.h
index 690e76570..0cb00dea6 100644
--- a/include/net/gen/ether.h
+++ b/include/net/gen/ether.h
@@ -17,7 +17,6 @@ typedef struct ether_addr
 } ether_addr_t;
 
 typedef u16_t ether_type_t;
-typedef U16_t Ether_type_t;
 
 #define ETH_ARP_PROTO	 0x806
 #define ETH_IP_PROTO	 0x800
diff --git a/include/net/gen/oneCsum.h b/include/net/gen/oneCsum.h
index b9de8fa1d..3bfae46ec 100644
--- a/include/net/gen/oneCsum.h
+++ b/include/net/gen/oneCsum.h
@@ -5,6 +5,6 @@ server/ip/gen/oneCsum.h
 #ifndef __SERVER__IP__GEN__ONECSUM_H__
 #define __SERVER__IP__GEN__ONECSUM_H__
 
-u16_t oneC_sum _ARGS(( U16_t prev, void *data, size_t data_len ));
+u16_t oneC_sum _ARGS(( u16_t prev, void *data, size_t data_len ));
 
 #endif /* __SERVER__IP__GEN__ONECSUM_H__ */
diff --git a/include/net/gen/resolv.h b/include/net/gen/resolv.h
index bd9060346..4ad157f50 100644
--- a/include/net/gen/resolv.h
+++ b/include/net/gen/resolv.h
@@ -99,7 +99,7 @@ char *__hostalias _ARGS(( const char *name ));
 
 u16_t _getshort _ARGS(( const u8_t *msgp ));
 u32_t _getlong _ARGS(( const u8_t *msgp ));
-void __putshort _ARGS(( U16_t s, u8_t *msgp ));
+void __putshort _ARGS(( u16_t s, u8_t *msgp ));
 void __putlong _ARGS(( u32_t l, u8_t *msgp ));
 
 void p_query _ARGS(( char *msg ));
diff --git a/include/net/gen/tcp.h b/include/net/gen/tcp.h
index 11022e330..05d016ac4 100644
--- a/include/net/gen/tcp.h
+++ b/include/net/gen/tcp.h
@@ -14,6 +14,5 @@ server/ip/gen/tcp.h
 #define TCPPORT_RESERVED	1024
 
 typedef u16_t tcpport_t;
-typedef U16_t Tcpport_t;	/* for use in prototypes */
 
 #endif /* __SERVER__IP__GEN__TCP_H__ */
diff --git a/include/net/gen/udp.h b/include/net/gen/udp.h
index a78dceb41..fae397a05 100644
--- a/include/net/gen/udp.h
+++ b/include/net/gen/udp.h
@@ -6,7 +6,6 @@ server/ip/gen/udp.h
 #define __SERVER__IP__GEN__UDP_H__
 
 typedef u16_t udpport_t;
-typedef U16_t Udpport_t;
 
 #define UDP_HDR_SIZE	8
 #define UDP_IO_HDR_SIZE	16
diff --git a/kernel/arch/i386/protect.c b/kernel/arch/i386/protect.c
index 802be8320..a746b1e5d 100644
--- a/kernel/arch/i386/protect.c
+++ b/kernel/arch/i386/protect.c
@@ -48,7 +48,7 @@ PUBLIC void enable_iop(struct proc *pp)
 /*===========================================================================*
  *				seg2phys				     *
  *===========================================================================*/
-PUBLIC phys_bytes seg2phys(const U16_t seg)
+PUBLIC phys_bytes seg2phys(const u16_t seg)
 {
 /* Return the base address of a segment, with seg being a 
  * register, or a 286/386 segment selector.
diff --git a/kernel/arch/i386/proto.h b/kernel/arch/i386/proto.h
index 7a8ed8356..e421510ce 100644
--- a/kernel/arch/i386/proto.h
+++ b/kernel/arch/i386/proto.h
@@ -75,10 +75,10 @@ _PROTOTYPE( void write_cr0, (unsigned long value)                       );
 _PROTOTYPE( unsigned long read_cr4, (void)                              );
 _PROTOTYPE( void write_cr4, (unsigned long value)                       );
 _PROTOTYPE( unsigned long read_cpu_flags, (void)                        );
-_PROTOTYPE( void phys_insb, (U16_t port, phys_bytes buf, size_t count)  );
-_PROTOTYPE( void phys_insw, (U16_t port, phys_bytes buf, size_t count)  );
-_PROTOTYPE( void phys_outsb, (U16_t port, phys_bytes buf, size_t count) );
-_PROTOTYPE( void phys_outsw, (U16_t port, phys_bytes buf, size_t count) );
+_PROTOTYPE( void phys_insb, (u16_t port, phys_bytes buf, size_t count)  );
+_PROTOTYPE( void phys_insw, (u16_t port, phys_bytes buf, size_t count)  );
+_PROTOTYPE( void phys_outsb, (u16_t port, phys_bytes buf, size_t count) );
+_PROTOTYPE( void phys_outsw, (u16_t port, phys_bytes buf, size_t count) );
 _PROTOTYPE( u32_t read_cr3, (void) );
 _PROTOTYPE( void reload_cr3, (void) );
 _PROTOTYPE( void phys_memset, (phys_bytes ph, u32_t c, phys_bytes bytes));
diff --git a/kernel/proto.h b/kernel/proto.h
index b8ff91a2c..da4e8c25a 100644
--- a/kernel/proto.h
+++ b/kernel/proto.h
@@ -53,8 +53,8 @@ _PROTOTYPE( int isokendpt_f, (endpoint_t e, int *p, int f)		);
 _PROTOTYPE( void check_ticks_left, (struct proc *p));
 
 /* start.c */
-_PROTOTYPE( void cstart, (U16_t cs, U16_t ds, U16_t mds,
-				U16_t parmoff, U16_t parmsize)		);
+_PROTOTYPE( void cstart, (u16_t cs, u16_t ds, u16_t mds,
+				u16_t parmoff, u16_t parmsize)		);
 
 /* system.c */
 _PROTOTYPE( int get_priv, (register struct proc *rc, int proc_type)	);
@@ -142,7 +142,7 @@ _PROTOTYPE( phys_bytes umap_remote, (const struct proc* rp, int seg,
         vir_bytes vir_addr, vir_bytes bytes)				);
 _PROTOTYPE( phys_bytes umap_virtual, (struct proc* rp,
 			int seg, vir_bytes vir_addr, vir_bytes bytes)	);
-_PROTOTYPE( phys_bytes seg2phys, (U16_t)                                );
+_PROTOTYPE( phys_bytes seg2phys, (u16_t)                                );
 _PROTOTYPE( int vm_phys_memset, (phys_bytes source, u8_t pattern,
                 phys_bytes count)                                       );
 _PROTOTYPE( vir_bytes alloc_remote_segment, (u32_t *, segframe_t *,
diff --git a/kernel/start.c b/kernel/start.c
index 75e875ee6..d70ac8878 100644
--- a/kernel/start.c
+++ b/kernel/start.c
@@ -15,10 +15,13 @@ FORWARD _PROTOTYPE( char *get_value, (const char *params, const char *key));
 /*===========================================================================*
  *				cstart					     *
  *===========================================================================*/
-PUBLIC void cstart(cs, ds, mds, parmoff, parmsize)
-U16_t cs, ds;			/* kernel code and data segment */
-U16_t mds;			/* monitor data segment */
-U16_t parmoff, parmsize;	/* boot parameters offset and length */
+PUBLIC void cstart(
+   u16_t cs,		/* kernel code segment */
+   u16_t ds,		/* kernel data segment */
+   u16_t mds,		/* monitor data segment */
+   u16_t parmoff,	/* boot parameters offset */
+   u16_t parmsize	/* boot parameters length */
+)
 {
 /* Perform system initializations prior to calling main(). Most settings are
  * determined with help of the environment strings passed by MINIX' loader.
@@ -111,9 +114,10 @@ U16_t parmoff, parmsize;	/* boot parameters offset and length */
  *				get_value				     *
  *===========================================================================*/
 
-PRIVATE char *get_value(params, name)
-  const char *params;				/* boot monitor parameters */
-  const char *name;				/* key to look up */
+PRIVATE char *get_value(
+  const char *params,			/* boot monitor parameters */
+  const char *name			/* key to look up */
+)
 {
 /* Get environment value - kernel version of getenv to avoid setting up the
  * usual environment array.
diff --git a/lib/libc/ip/oneC_sum.c b/lib/libc/ip/oneC_sum.c
index cc3d9af09..702b9d35b 100644
--- a/lib/libc/ip/oneC_sum.c
+++ b/lib/libc/ip/oneC_sum.c
@@ -6,7 +6,7 @@
 #include <sys/types.h>
 #include <net/gen/oneCsum.h>
 
-u16_t oneC_sum(U16_t prev, void *data, size_t size)
+u16_t oneC_sum(u16_t prev, void *data, size_t size)
 {
 	u8_t *dptr;
 	size_t n;
diff --git a/lib/libc/ip/res_comp.c b/lib/libc/ip/res_comp.c
index 0b4574027..66b772b7d 100644
--- a/lib/libc/ip/res_comp.c
+++ b/lib/libc/ip/res_comp.c
@@ -42,7 +42,7 @@ int dn_skipname _ARGS(( const u_char *comp_dn, const u_char *eom ));
 #include <stdio.h>
 #include <arpa/nameser.h>
 
-static dn_find();
+static int dn_find();
 #endif
 
 #ifdef __STDC__
@@ -325,9 +325,7 @@ getlong(msgp)
 
 
 void
-putshort(s, msgp)
-	register U16_t s;
-	register u8_t *msgp;
+putshort(u16_t s, u8_t *msgp)
 {
 
 	msgp[1] = s;
@@ -335,9 +333,7 @@ putshort(s, msgp)
 }
 
 void
-putlong(l, msgp)
-	register u32_t l;
-	register u8_t *msgp;
+putlong(u32_t l, u8_t *msgp)
 {
 
 	msgp[3] = l;
diff --git a/lib/libc/ip/res_send.c b/lib/libc/ip/res_send.c
index 88090f3f1..5bc3101f9 100644
--- a/lib/libc/ip/res_send.c
+++ b/lib/libc/ip/res_send.c
@@ -81,11 +81,9 @@ static char sccsid[] = "@(#)res_send.c	6.27 (Berkeley) 2/24/91";
 #include <net/gen/udp_hdr.h>
 #include <net/gen/udp_io.h>
 
-static int tcp_connect _ARGS(( ipaddr_t host, Tcpport_t port, int *terrno ));
-static int tcpip_writeall _ARGS(( int fd, const char *buf, size_t siz ));
 static int udp_connect _ARGS(( void ));
 static int udp_sendto _ARGS(( int fd, const char *buf, unsigned buflen,
-				ipaddr_t addr, Udpport_t port ));
+				ipaddr_t addr, udpport_t port ));
 static int udp_receive _ARGS(( int fd, char *buf, unsigned buflen,
 				time_t timeout ));
 
@@ -718,10 +716,7 @@ _res_close()
 }
 
 #if _MINIX
-static int tcp_connect(host, port, terrno)
-ipaddr_t host;
-tcpport_t port;
-int *terrno;
+static int tcp_connect(ipaddr_t host, tcpport_t port, int *terrno)
 {
 	char *dev_name;
 	int fd;
@@ -810,12 +805,13 @@ static int udp_connect()
 	return fd;
 }
 
-static int udp_sendto(fd, buf, buflen, addr, port)
-int fd;
-const char *buf;
-unsigned buflen;
-ipaddr_t addr;
-udpport_t port;
+static int udp_sendto(
+  int fd,
+  const char *buf,
+  unsigned buflen,
+  ipaddr_t addr,
+  udpport_t port
+)
 {
 	char *newbuf;
 	udp_io_hdr_t *udp_io_hdr;
@@ -843,11 +839,7 @@ udpport_t port;
 	return r;
 }
 
-static int udp_receive(fd, buf, buflen, timeout)
-int fd;
-char *buf;
-unsigned buflen;
-time_t timeout;
+static int udp_receive(int fd, char *buf, unsigned buflen, time_t timeout)
 {
 	char *newbuf;
 	udp_io_hdr_t *udp_io_hdr;
diff --git a/lib/libc/other/getgrent.c b/lib/libc/other/getgrent.c
index 54978ac99..b2095e2fb 100644
--- a/lib/libc/other/getgrent.c
+++ b/lib/libc/other/getgrent.c
@@ -3,7 +3,6 @@
  *							Author: Kees J. Bot
  *								31 Jan 1994
  */
-#define nil 0
 #define open _open
 #define fcntl _fcntl
 #define read _read
@@ -45,7 +44,7 @@ int setgrent(void)
 {
 	if (grfd >= 0) endgrent();
 
-	if (grfile == nil) grfile= GROUP;
+	if (grfile == NULL) grfile= GROUP;
 
 	if ((grfd= open(grfile, O_RDONLY)) < 0) return -1;
 	(void) fcntl(grfd, F_SETFD, fcntl(grfd, F_GETFD) | FD_CLOEXEC);
@@ -87,10 +86,10 @@ static char *scan_punct(int punct)
 
 	for (;;) {
 		last= lineptr;
-		if (*lineptr == 0) return nil;
+		if (*lineptr == 0) return NULL;
 		if (*lineptr == '\n') break;
 		if (*lineptr++ == punct) break;
-		if (lineptr[-1] == ':') return nil;	/* :::,,,:,,,? */
+		if (lineptr[-1] == ':') return NULL;	/* :::,,,:,,,? */
 	}
 	*last= 0;
 	return field;
@@ -103,25 +102,25 @@ struct group *getgrent(void)
 	char **mem;
 
 	/* Open the file if not yet open. */
-	if (grfd < 0 && setgrent() < 0) return nil;
+	if (grfd < 0 && setgrent() < 0) return NULL;
 
 	/* Until a good line is read. */
 	for (;;) {
-		if (!getline()) return nil;	/* EOF or corrupt. */
+		if (!getline()) return NULL;	/* EOF or corrupt. */
 
-		if ((entry.gr_name= scan_punct(':')) == nil) continue;
-		if ((entry.gr_passwd= scan_punct(':')) == nil) continue;
-		if ((p= scan_punct(':')) == nil) continue;
-		entry.gr_gid= strtol(p, nil, 0);
+		if ((entry.gr_name= scan_punct(':')) == NULL) continue;
+		if ((entry.gr_passwd= scan_punct(':')) == NULL) continue;
+		if ((p= scan_punct(':')) == NULL) continue;
+		entry.gr_gid= strtol(p, NULL, 0);
 
 		entry.gr_mem= mem= members;
 		if (*lineptr != '\n') {
 			do {
-				if ((*mem= scan_punct(',')) == nil) goto again;
+				if ((*mem= scan_punct(',')) == NULL) goto again;
 				if (mem < arraylimit(members) - 1) mem++;
 			} while (*lineptr != 0);
 		}
-		*mem= nil;
+		*mem= NULL;
 		return &entry;
 	again:;
 	}
@@ -133,7 +132,7 @@ struct group *getgrgid(gid_t gid)
 	struct group *gr;
 
 	endgrent();
-	while ((gr= getgrent()) != nil && gr->gr_gid != gid) {}
+	while ((gr= getgrent()) != NULL && gr->gr_gid != gid) {}
 	endgrent();
 	return gr;
 }
@@ -144,7 +143,7 @@ struct group *getgrnam(const char *name)
 	struct group *gr;
 
 	endgrent();
-	while ((gr= getgrent()) != nil && strcmp(gr->gr_name, name) != 0) {}
+	while ((gr= getgrent()) != NULL && strcmp(gr->gr_name, name) != 0) {}
 	endgrent();
 	return gr;
 }
diff --git a/lib/libc/other/getpwent.c b/lib/libc/other/getpwent.c
index 22e5dfe87..d5a7e9b2b 100644
--- a/lib/libc/other/getpwent.c
+++ b/lib/libc/other/getpwent.c
@@ -3,7 +3,6 @@
  *							Author: Kees J. Bot
  *								31 Jan 1994
  */
-#define nil 0
 #define open _open
 #define fcntl _fcntl
 #define read _read
@@ -44,7 +43,7 @@ int setpwent(void)
 {
 	if (pwfd >= 0) endpwent();
 
-	if (pwfile == nil) pwfile= PASSWD;
+	if (pwfile == NULL) pwfile= PASSWD;
 
 	if ((pwfd= open(pwfile, O_RDONLY)) < 0) return -1;
 	(void) fcntl(pwfd, F_SETFD, fcntl(pwfd, F_GETFD) | FD_CLOEXEC);
@@ -86,7 +85,7 @@ static char *scan_colon(void)
 
 	for (;;) {
 		last= lineptr;
-		if (*lineptr == 0) return nil;
+		if (*lineptr == 0) return NULL;
 		if (*lineptr == '\n') break;
 		if (*lineptr++ == ':') break;
 	}
@@ -100,21 +99,21 @@ struct passwd *getpwent(void)
 	char *p;
 
 	/* Open the file if not yet open. */
-	if (pwfd < 0 && setpwent() < 0) return nil;
+	if (pwfd < 0 && setpwent() < 0) return NULL;
 
 	/* Until a good line is read. */
 	for (;;) {
-		if (!getline()) return nil;	/* EOF or corrupt. */
+		if (!getline()) return NULL;	/* EOF or corrupt. */
 
-		if ((entry.pw_name= scan_colon()) == nil) continue;
-		if ((entry.pw_passwd= scan_colon()) == nil) continue;
-		if ((p= scan_colon()) == nil) continue;
-		entry.pw_uid= strtol(p, nil, 0);
-		if ((p= scan_colon()) == nil) continue;
-		entry.pw_gid= strtol(p, nil, 0);
-		if ((entry.pw_gecos= scan_colon()) == nil) continue;
-		if ((entry.pw_dir= scan_colon()) == nil) continue;
-		if ((entry.pw_shell= scan_colon()) == nil) continue;
+		if ((entry.pw_name= scan_colon()) == NULL) continue;
+		if ((entry.pw_passwd= scan_colon()) == NULL) continue;
+		if ((p= scan_colon()) == NULL) continue;
+		entry.pw_uid= strtol(p, NULL, 0);
+		if ((p= scan_colon()) == NULL) continue;
+		entry.pw_gid= strtol(p, NULL, 0);
+		if ((entry.pw_gecos= scan_colon()) == NULL) continue;
+		if ((entry.pw_dir= scan_colon()) == NULL) continue;
+		if ((entry.pw_shell= scan_colon()) == NULL) continue;
 
 		if (*lineptr == 0) return &entry;
 	}
@@ -126,7 +125,7 @@ struct passwd *getpwuid(uid_t uid)
 	struct passwd *pw;
 
 	endpwent();
-	while ((pw= getpwent()) != nil && pw->pw_uid != uid) {}
+	while ((pw= getpwent()) != NULL && pw->pw_uid != uid) {}
 	endpwent();
 	return pw;
 }
@@ -137,7 +136,7 @@ struct passwd *getpwnam(const char *name)
 	struct passwd *pw;
 
 	endpwent();
-	while ((pw= getpwent()) != nil && strcmp(pw->pw_name, name) != 0) {}
+	while ((pw= getpwent()) != NULL && strcmp(pw->pw_name, name) != 0) {}
 	endpwent();
 	return pw;
 }
diff --git a/lib/libc/posix/_getcwd.c b/lib/libc/posix/_getcwd.c
index 6dcca5d85..17117ca56 100644
--- a/lib/libc/posix/_getcwd.c
+++ b/lib/libc/posix/_getcwd.c
@@ -2,7 +2,6 @@
  *							Author: Kees J. Bot
  *								30 Apr 1989
  */
-#define nil 0
 #define chdir _chdir
 #define closedir _closedir
 #define getcwd _getcwd
@@ -65,22 +64,22 @@ char *getcwd(char *path, size_t size)
 	char *p, *up, *dotdot;
 	int cycle;
 
-	if (path == nil || size <= 1) { errno= EINVAL; return nil; }
+	if (path == NULL || size <= 1) { errno= EINVAL; return NULL; }
 
 	p= path + size;
 	*--p = 0;
 
-	if (stat(".", &current) < 0) return nil;
+	if (stat(".", &current) < 0) return NULL;
 
 	while (1) {
 		dotdot= "..";
-		if (stat(dotdot, &above) < 0) { recover(p); return nil; }
+		if (stat(dotdot, &above) < 0) { recover(p); return NULL; }
 
 		if (above.st_dev == current.st_dev
 					&& above.st_ino == current.st_ino)
 			break;	/* Root dir found */
 
-		if ((d= opendir(dotdot)) == nil) { recover(p); return nil; }
+		if ((d= opendir(dotdot)) == NULL) { recover(p); return NULL; }
 
 		/* Cycle is 0 for a simple inode nr search, or 1 for a search
 		 * for inode *and* device nr.
@@ -91,7 +90,7 @@ char *getcwd(char *path, size_t size)
 			char name[3 + NAME_MAX + 1];
 
 			tmp.st_ino= 0;
-			if ((entry= readdir(d)) == nil) {
+			if ((entry= readdir(d)) == NULL) {
 				switch (++cycle) {
 				case 1:
 					rewinddir(d);
@@ -100,7 +99,7 @@ char *getcwd(char *path, size_t size)
 					closedir(d);
 					errno= ENOENT;
 					recover(p);
-					return nil;
+					return NULL;
 				}
 			}
 			if (strcmp(entry->d_name, ".") == 0) continue;
@@ -127,16 +126,16 @@ char *getcwd(char *path, size_t size)
 			closedir(d);
 			errno = ERANGE;
 			recover(p);
-			return nil;
+			return NULL;
 		}
 		closedir(d);
 
-		if (chdir(dotdot) < 0) { recover(p); return nil; }
+		if (chdir(dotdot) < 0) { recover(p); return NULL; }
 		p= up;
 
 		current= above;
 	}
-	if (recover(p) < 0) return nil;	/* Undo all those chdir("..")'s. */
+	if (recover(p) < 0) return NULL;	/* Undo all those chdir("..")'s. */
 	if (*p == 0) *--p = '/';	/* Cwd is "/" if nothing added */
 	if (p > path) strcpy(path, p);	/* Move string to start of path. */
 	return path;
diff --git a/lib/libc/posix/_ptrace.c b/lib/libc/posix/_ptrace.c
index d4d7f52b9..c33059eef 100644
--- a/lib/libc/posix/_ptrace.c
+++ b/lib/libc/posix/_ptrace.c
@@ -2,11 +2,7 @@
 #define ptrace	_ptrace
 #include <unistd.h>
 
-PUBLIC long ptrace(req, pid, addr, data)
-int req;
-pid_t pid;
-long addr;
-long data;
+PUBLIC long ptrace(int req, pid_t pid, long addr, long data)
 {
   message m;
 
diff --git a/servers/inet/generic/icmp.c b/servers/inet/generic/icmp.c
index 855389a33..c7a10da9b 100644
--- a/servers/inet/generic/icmp.c
+++ b/servers/inet/generic/icmp.c
@@ -371,10 +371,11 @@ int code;
 	enqueue_pack(icmp_port, pack);
 }
 
-PUBLIC void icmp_snd_mtu(port_nr, pack, mtu)
-int port_nr;
-acc_t *pack;
-u16_t mtu;
+PUBLIC void icmp_snd_mtu(
+  int port_nr,
+  acc_t *pack,
+  u16_t mtu
+)
 {
 	icmp_hdr_t *icmp_hdr;
 	icmp_port_t *icmp_port;
diff --git a/servers/inet/generic/icmp_lib.h b/servers/inet/generic/icmp_lib.h
index 7501f1a7a..8601ff499 100644
--- a/servers/inet/generic/icmp_lib.h
+++ b/servers/inet/generic/icmp_lib.h
@@ -16,7 +16,7 @@ void icmp_snd_time_exceeded ARGS(( int port_nr, acc_t *pack, int code ));
 void icmp_snd_unreachable ARGS(( int port_nr, acc_t *pack, int code ));
 void icmp_snd_redirect ARGS(( int port_nr, acc_t *pack, int code,
 							ipaddr_t gw ));
-void icmp_snd_mtu ARGS(( int port_nr, acc_t *pack, U16_t mtu ));
+void icmp_snd_mtu ARGS(( int port_nr, acc_t *pack, u16_t mtu ));
 
 #endif /* ICMP_LIB_H */
 
diff --git a/servers/inet/generic/ip_lib.c b/servers/inet/generic/ip_lib.c
index a9f6114c8..a921686c4 100644
--- a/servers/inet/generic/ip_lib.c
+++ b/servers/inet/generic/ip_lib.c
@@ -15,15 +15,12 @@ Copyright 1995 Philip Homburg
 
 THIS_FILE
 
-PUBLIC ipaddr_t ip_get_netmask (hostaddr)
-ipaddr_t hostaddr;
+PUBLIC ipaddr_t ip_get_netmask (ipaddr_t hostaddr)
 {
 	return ip_netmask(ip_nettype(hostaddr));
 }
 
-PUBLIC int ip_chk_hdropt (opt, optlen)
-u8_t *opt;
-int optlen;
+PUBLIC int ip_chk_hdropt (u8_t *opt, int optlen)
 {
 	int i, security_present= FALSE, lose_source_present= FALSE,
 		strict_source_present= FALSE, record_route_present= FALSE,
@@ -122,8 +119,7 @@ int optlen;
 	return NW_OK;
 }
 
-PUBLIC void ip_print_frags(acc)
-acc_t *acc;
+PUBLIC void ip_print_frags(acc_t *acc)
 {
 #if DEBUG
 	ip_hdr_t *ip_hdr;
@@ -151,16 +147,14 @@ assert (acc->acc_length >= IP_MIN_HDR_SIZE);
 #endif
 }
 
-PUBLIC ipaddr_t ip_get_ifaddr(port_nr)
-int port_nr;
+PUBLIC ipaddr_t ip_get_ifaddr(int port_nr)
 {
 	assert(port_nr >= 0 && port_nr < ip_conf_nr);
 
 	return ip_port_table[port_nr].ip_ipaddr;
 }
 
-PUBLIC nettype_t ip_nettype(ipaddr)
-ipaddr_t ipaddr;
+PUBLIC nettype_t ip_nettype(ipaddr_t ipaddr)
 {
 	u8_t highbyte;
 	nettype_t nettype;
@@ -198,8 +192,7 @@ ipaddr_t ipaddr;
 	return nettype;
 }
 
-PUBLIC ipaddr_t ip_netmask(nettype)
-nettype_t nettype;
+PUBLIC ipaddr_t ip_netmask(nettype_t nettype)
 {
 	switch(nettype)
 	{
@@ -213,8 +206,7 @@ nettype_t nettype;
 }
 
 #if 0
-PUBLIC char *ip_nettoa(nettype)
-nettype_t nettype;
+PUBLIC char *ip_nettoa(nettype_t nettype)
 {
 	switch(nettype)
 	{
diff --git a/servers/inet/generic/ip_read.c b/servers/inet/generic/ip_read.c
index 67fe32f22..5bb89c400 100644
--- a/servers/inet/generic/ip_read.c
+++ b/servers/inet/generic/ip_read.c
@@ -28,9 +28,7 @@ FORWARD acc_t *reassemble ARGS(( ip_port_t *ip_port, acc_t *pack,
 FORWARD void route_packets ARGS(( event_t *ev, ev_arg_t ev_arg ));
 FORWARD int broadcast_dst ARGS(( ip_port_t *ip_port, ipaddr_t dest ));
 
-PUBLIC int ip_read (fd, count)
-int fd;
-size_t count;
+PUBLIC int ip_read(int fd, size_t count)
 {
 	ip_fd_t *ip_fd;
 	acc_t *pack;
diff --git a/servers/inet/generic/ipr.c b/servers/inet/generic/ipr.c
index 6a3013a15..5aaaaa546 100644
--- a/servers/inet/generic/ipr.c
+++ b/servers/inet/generic/ipr.c
@@ -651,11 +651,12 @@ time_t timeout;
 	assert(result == NW_OK);
 }
 
-PUBLIC void ipr_mtu(port_nr, dest, mtu, timeout)
-int port_nr;
-ipaddr_t dest;
-u16_t mtu;
-time_t timeout;
+PUBLIC void ipr_mtu(
+  int port_nr,
+  ipaddr_t dest,
+  u16_t mtu,
+  time_t timeout
+)
 {
 	oroute_t *oroute;
 	int result;
diff --git a/servers/inet/generic/ipr.h b/servers/inet/generic/ipr.h
index bece6b056..8f06cf762 100644
--- a/servers/inet/generic/ipr.h
+++ b/servers/inet/generic/ipr.h
@@ -81,7 +81,7 @@ void ipr_destunrch ARGS(( int port_nr, ipaddr_t dest, ipaddr_t subnetmask,
 	time_t timeout ));
 void ipr_ttl_exc ARGS(( int port_nr, ipaddr_t dest, ipaddr_t subnetmask,
 	time_t timeout ));
-void ipr_mtu ARGS(( int port_nr, ipaddr_t dest, U16_t mtu, time_t timeout ));
+void ipr_mtu ARGS(( int port_nr, ipaddr_t dest, u16_t mtu, time_t timeout ));
 
 #endif /* IPR_H */
 
diff --git a/servers/inet/generic/tcp.c b/servers/inet/generic/tcp.c
index 976bbfeca..25e686a6a 100644
--- a/servers/inet/generic/tcp.c
+++ b/servers/inet/generic/tcp.c
@@ -39,19 +39,19 @@ FORWARD int tcp_connect ARGS(( tcp_fd_t *tcp_fd ));
 FORWARD int tcp_listen ARGS(( tcp_fd_t *tcp_fd, int do_listenq ));
 FORWARD int tcp_acceptto ARGS(( tcp_fd_t *tcp_fd ));
 FORWARD tcpport_t find_unused_port ARGS(( int fd ));
-FORWARD int is_unused_port ARGS(( Tcpport_t port ));
+FORWARD int is_unused_port ARGS(( tcpport_t port ));
 FORWARD int reply_thr_put ARGS(( tcp_fd_t *tcp_fd, int reply,
 	int for_ioctl ));
 FORWARD void reply_thr_get ARGS(( tcp_fd_t *tcp_fd, int reply,
 	int for_ioctl ));
-FORWARD tcp_conn_t *find_conn_entry ARGS(( Tcpport_t locport,
-	ipaddr_t locaddr, Tcpport_t remport, ipaddr_t readaddr ));
+FORWARD tcp_conn_t *find_conn_entry ARGS(( tcpport_t locport,
+	ipaddr_t locaddr, tcpport_t remport, ipaddr_t readaddr ));
 FORWARD tcp_conn_t *find_empty_conn ARGS(( void ));
 FORWARD tcp_conn_t *find_best_conn ARGS(( ip_hdr_t *ip_hdr, 
 	tcp_hdr_t *tcp_hdr ));
 FORWARD tcp_conn_t *new_conn_for_queue ARGS(( tcp_fd_t *tcp_fd ));
-FORWARD int maybe_listen ARGS(( ipaddr_t locaddr, Tcpport_t locport,
-				ipaddr_t remaddr, Tcpport_t remport ));
+FORWARD int maybe_listen ARGS(( ipaddr_t locaddr, tcpport_t locport,
+				ipaddr_t remaddr, tcpport_t remport ));
 FORWARD int tcp_su4connect ARGS(( tcp_fd_t *tcp_fd ));
 FORWARD void tcp_buffree ARGS(( int priority ));
 #ifdef BUF_CONSISTENCY_CHECK
@@ -1276,8 +1276,7 @@ assert (data->acc_length == sizeof(nwio_tcpopt_t));
 }
 
 
-PRIVATE tcpport_t find_unused_port(fd)
-int fd;
+PRIVATE tcpport_t find_unused_port(int fd)
 {
 	tcpport_t port, nw_port;
 
@@ -1297,8 +1296,7 @@ int fd;
 	return 0;
 }
 
-PRIVATE int is_unused_port(port)
-tcpport_t port;
+PRIVATE int is_unused_port(tcpport_t port)
 {
 	int i;
 	tcp_fd_t *tcp_fd;
@@ -1426,11 +1424,12 @@ If no such connection exists NULL is returned.
 If a connection exists without mainuser it is closed.
 */
 
-PRIVATE tcp_conn_t *find_conn_entry(locport, locaddr, remport, remaddr)
-tcpport_t locport;
-ipaddr_t locaddr;
-tcpport_t remport;
-ipaddr_t remaddr;
+PRIVATE tcp_conn_t *find_conn_entry(
+  tcpport_t locport,
+  ipaddr_t locaddr,
+  tcpport_t remport,
+  ipaddr_t remaddr
+)
 {
 	tcp_conn_t *tcp_conn;
 	int i, state;
@@ -1682,11 +1681,12 @@ tcp_fd_t *tcp_fd;
 /*
 maybe_listen
 */
-PRIVATE int maybe_listen(locaddr, locport, remaddr, remport)
-ipaddr_t locaddr;
-tcpport_t locport;
-ipaddr_t remaddr;
-tcpport_t remport;
+PRIVATE int maybe_listen(
+  ipaddr_t locaddr,
+  tcpport_t locport,
+  ipaddr_t remaddr,
+  tcpport_t remport
+)
 {
 	int i;
 	tcp_conn_t *tcp_conn;
diff --git a/servers/inet/generic/tcp_int.h b/servers/inet/generic/tcp_int.h
index 9c5b17c17..58cf174a2 100644
--- a/servers/inet/generic/tcp_int.h
+++ b/servers/inet/generic/tcp_int.h
@@ -204,7 +204,7 @@ void tcp_bytesavailable ARGS(( tcp_fd_t *tcp_fd, int *bytesp ));
 /* tcp_send.c */
 void tcp_conn_write ARGS(( tcp_conn_t *tcp_conn, int enq ));
 void tcp_release_retrans ARGS(( tcp_conn_t *tcp_conn, u32_t seg_ack,
-	U16_t new_win ));
+	u16_t new_win ));
 void tcp_fast_retrans ARGS(( tcp_conn_t *tcp_conn ));
 void tcp_set_send_timer ARGS(( tcp_conn_t *tcp_conn ));
 void tcp_fd_write ARGS(( tcp_conn_t *tcp_conn ));
diff --git a/servers/inet/generic/tcp_send.c b/servers/inet/generic/tcp_send.c
index a10cf8aa5..e63cf368c 100644
--- a/servers/inet/generic/tcp_send.c
+++ b/servers/inet/generic/tcp_send.c
@@ -530,10 +530,11 @@ after_data:
 tcp_release_retrans
 */
 
-PUBLIC void tcp_release_retrans(tcp_conn, seg_ack, new_win)
-tcp_conn_t *tcp_conn;
-u32_t seg_ack;
-u16_t new_win;
+PUBLIC void tcp_release_retrans(
+  tcp_conn_t *tcp_conn,
+  u32_t seg_ack,
+  u16_t new_win
+)
 {
 	tcp_fd_t *tcp_fd;
 	size_t size, offset;
diff --git a/servers/inet/generic/udp.c b/servers/inet/generic/udp.c
index 7b511ea10..99e8f99b5 100644
--- a/servers/inet/generic/udp.c
+++ b/servers/inet/generic/udp.c
@@ -40,7 +40,7 @@ FORWARD void reply_thr_get ARGS(( udp_fd_t *udp_fd, int reply,
 	int for_ioctl ));
 FORWARD int udp_setopt ARGS(( udp_fd_t *udp_fd ));
 FORWARD udpport_t find_unused_port ARGS(( int fd ));
-FORWARD int is_unused_port ARGS(( Udpport_t port ));
+FORWARD int is_unused_port ARGS(( udpport_t port ));
 FORWARD int udp_packet2user ARGS(( udp_fd_t *udp_fd ));
 FORWARD void restart_write_fd ARGS(( udp_fd_t *udp_fd ));
 FORWARD u16_t pack_oneCsum ARGS(( acc_t *pack ));
@@ -676,8 +676,7 @@ assert (data->acc_length == sizeof(nwio_udpopt_t));
 	return NW_OK;
 }
 
-PRIVATE udpport_t find_unused_port(fd)
-int fd;
+PRIVATE udpport_t find_unused_port(int fd)
 {
 	udpport_t port, nw_port;
 
@@ -728,8 +727,7 @@ int for_ioctl;
 	assert (!result);
 }
 
-PRIVATE int is_unused_port(port)
-udpport_t port;
+PRIVATE int is_unused_port(udpport_t port)
 {
 	int i;
 	udp_fd_t *udp_fd;
diff --git a/servers/vfs/exec.c b/servers/vfs/exec.c
index ec7995317..1739f1178 100644
--- a/servers/vfs/exec.c
+++ b/servers/vfs/exec.c
@@ -253,16 +253,16 @@ PRIVATE int exec_newmem(
 /*===========================================================================*
  *				read_header				     *
  *===========================================================================*/
-PRIVATE int read_header(vp, sep_id, text_bytes, data_bytes, bss_bytes, 
-						tot_bytes, pc, hdrlenp)
-struct vnode *vp;		/* inode for reading exec file */
-int *sep_id;			/* true iff sep I&D */
-vir_bytes *text_bytes;		/* place to return text size */
-vir_bytes *data_bytes;		/* place to return initialized data size */
-vir_bytes *bss_bytes;		/* place to return bss size */
-phys_bytes *tot_bytes;		/* place to return total size */
-vir_bytes *pc;			/* program entry point (initial PC) */
-int *hdrlenp;
+PRIVATE int read_header(
+  struct vnode *vp,		/* inode for reading exec file */
+  int *sep_id,			/* true iff sep I&D */
+  vir_bytes *text_bytes,	/* place to return text size */
+  vir_bytes *data_bytes,	/* place to return initialized data size */
+  vir_bytes *bss_bytes,		/* place to return bss size */
+  phys_bytes *tot_bytes,	/* place to return total size */
+  vir_bytes *pc,		/* program entry point (initial PC) */
+  int *hdrlenp
+)
 {
 /* Read the header and extract the text, data, bss and total sizes from it. */
   off_t pos;
diff --git a/servers/vfs/mount.c b/servers/vfs/mount.c
index 6bf948dc5..b2089acdf 100644
--- a/servers/vfs/mount.c
+++ b/servers/vfs/mount.c
@@ -371,7 +371,7 @@ PRIVATE int mount_fs(endpoint_t fs_e)
 /*===========================================================================*
  *                              do_umount                                    *
  *===========================================================================*/
-PUBLIC int do_umount()
+PUBLIC int do_umount(void)
 {
 /* Perform the umount(name) system call. */
   char label[LABEL_MAX];
@@ -487,8 +487,7 @@ PUBLIC int unmount(
 /*===========================================================================*
  *                              name_to_dev                                  *
  *===========================================================================*/
-PRIVATE dev_t name_to_dev(allow_mountpt)
-int allow_mountpt;
+PRIVATE dev_t name_to_dev(int allow_mountpt)
 {
 /* Convert the block special file in 'user_fullpath' to a device number.
  * If the given path is not a block special file, but 'allow_mountpt' is set
@@ -533,7 +532,7 @@ PRIVATE int is_nonedev(dev_t dev)
 /*===========================================================================*
  *                              find_free_nonedev			     *
  *===========================================================================*/
-PRIVATE dev_t find_free_nonedev()
+PRIVATE dev_t find_free_nonedev(void)
 {
 /* Find a free "none" pseudo device. Do not allocate it yet.
  */
diff --git a/servers/vfs/request.c b/servers/vfs/request.c
index 73e948c29..329c7cef4 100644
--- a/servers/vfs/request.c
+++ b/servers/vfs/request.c
@@ -135,7 +135,7 @@ PUBLIC int req_chown(
 /*===========================================================================*
  *				req_create				     *
  *===========================================================================*/
-int req_create(
+PUBLIC int req_create(
   int fs_e,
   ino_t inode_nr,
   int omode,
@@ -204,10 +204,7 @@ PUBLIC int req_flush(endpoint_t fs_e, dev_t dev)
 /*===========================================================================*
  *				req_fstatfs	    			     *
  *===========================================================================*/
-PUBLIC int req_fstatfs(fs_e, who_e, buf)
-int fs_e;
-int who_e;
-char *buf;
+PUBLIC int req_fstatfs(int fs_e, int who_e, char *buf)
 {
   int r;
   cp_grant_id_t grant_id;
@@ -233,11 +230,7 @@ char *buf;
 /*===========================================================================*
  *				req_ftrunc	     			     *
  *===========================================================================*/
-PUBLIC int req_ftrunc(fs_e, inode_nr, start, end)
-endpoint_t fs_e;
-ino_t inode_nr;
-off_t start;
-off_t end;
+PUBLIC int req_ftrunc(endpoint_t fs_e, ino_t inode_nr, off_t start, off_t end)
 {
   message m;
 
@@ -257,13 +250,14 @@ off_t end;
 /*===========================================================================*
  *				req_getdents	     			     *
  *===========================================================================*/
-PUBLIC int req_getdents(fs_e, inode_nr, pos, buf, size, new_pos)
-endpoint_t fs_e;
-ino_t inode_nr;
-u64_t pos;
-char *buf;
-size_t size;
-u64_t *new_pos;
+PUBLIC int req_getdents(
+  endpoint_t fs_e,
+  ino_t inode_nr,
+  u64_t pos,
+  char *buf,
+  size_t size,
+  u64_t *new_pos
+)
 {
   int r;
   message m;
@@ -295,9 +289,7 @@ u64_t *new_pos;
 /*===========================================================================*
  *				req_inhibread	  			     *
  *===========================================================================*/
-PUBLIC int req_inhibread(fs_e, inode_nr)
-endpoint_t fs_e;
-ino_t inode_nr;
+PUBLIC int req_inhibread(endpoint_t fs_e, ino_t inode_nr)
 {
   message m;
 
@@ -313,18 +305,18 @@ ino_t inode_nr;
 /*===========================================================================*
  *				req_link	       			     *
  *===========================================================================*/
-PUBLIC int req_link(fs_e, link_parent, lastc, linked_file)
-endpoint_t fs_e;
-ino_t link_parent;
-char *lastc;
-ino_t linked_file;
+PUBLIC int req_link(
+  endpoint_t fs_e,
+  ino_t link_parent,
+  char *lastc,
+  ino_t linked_file
+)
 {
   int r;
   cp_grant_id_t grant_id;
-  size_t len;
+  const size_t len = strlen(lastc) + 1;
   message m;
 
-  len = strlen(lastc) + 1;
   grant_id = cpf_grant_direct(fs_e, (vir_bytes)lastc, len, CPF_READ);
   if(grant_id == -1)
 	  panic("req_link: cpf_grant_direct failed");
@@ -526,9 +518,7 @@ PUBLIC int req_mknod(
 /*===========================================================================*
  *				req_mountpoint	                 	     *
  *===========================================================================*/
-PUBLIC int req_mountpoint(fs_e, inode_nr)
-endpoint_t fs_e;
-ino_t inode_nr;
+PUBLIC int req_mountpoint(endpoint_t fs_e, ino_t inode_nr)
 {
   message m;