--- /sys/src/9k/k10/mmu.c
+++ /sys/src/9k/k10/mmu.c
@@ -197,7 +197,7 @@ mmuput(uintptr va, uintmem pa, Page*)
 				break;
 		}
 		if(page == nil){
-			if(up->mmuptp[0] == 0){
+			if(up->mmuptp[0] == nil){
 				page = mmuptpalloc();
 			}
 			else {
--- /sys/src/9k/port/fault.c
+++ /sys/src/9k/port/fault.c
@@ -23,7 +23,7 @@ fault(uintptr addr, int read)
 	m->pfault++;
 	for(;;) {
 		s = seg(up, addr, 1);		/* leaves s->lk qlocked if seg != nil */
-		if(s == 0) {
+		if(s == nil) {
 			up->psstate = sps;
 			return -1;
 		}
@@ -80,7 +80,7 @@ fixfault(Segment *s, uintptr addr, int read, int dommuput)
 	addr &= ~(pgsize-1);
 	soff = addr-s->base;
 	p = &s->map[soff/s->ptemapmem];
-	if(*p == 0)
+	if(*p == nil)
 		*p = ptealloc();
 
 	etp = *p;
@@ -109,7 +109,7 @@ fixfault(Segment *s, uintptr addr, int read, int dommuput)
 	case SG_BSS:
 	case SG_SHARED:			/* Zero fill on demand */
 	case SG_STACK:
-		if(*pg == 0) {
+		if(*pg == nil) {
 			new = newpage(1, s, addr, 1);
 			if(new == nil)
 				return -1;
@@ -159,7 +159,7 @@ fixfault(Segment *s, uintptr addr, int read, int dommuput)
 		break;
 
 	case SG_PHYSICAL:
-		if(*pg == 0) {
+		if(*pg == nil) {
 			fn = s->pseg->pgalloc;
 			if(fn)
 				*pg = (*fn)(s, addr);
@@ -327,7 +327,7 @@ seg(Proc *p, uintptr addr, int dolock)
 	et = &p->seg[NSEG];
 	for(s = p->seg; s < et; s++) {
 		n = *s;
-		if(n == 0)
+		if(n == nil)
 			continue;
 		if(addr >= n->base && addr < n->top) {
 			if(dolock == 0)
--- /sys/src/9k/port/page.c
+++ /sys/src/9k/port/page.c
@@ -101,8 +101,8 @@ if(pm->limit > 600*MiB)
 		}
 	}
 	palloc.tail = p - 1;
-	palloc.head->prev = 0;
-	palloc.tail->next = 0;
+	palloc.head->prev = nil;
+	palloc.tail->next = nil;
 
 	palloc.user = p - palloc.pages;
 
@@ -149,10 +149,10 @@ pagechaintail(Page *p)
 	}
 	else {
 		palloc.head = p;
-		p->prev = 0;
+		p->prev = nil;
 	}
 	palloc.tail = p;
-	p->next = 0;
+	p->next = nil;
 	palloc.freecount++;
 }
 
@@ -167,10 +167,10 @@ pagechainhead(Page *p)
 	}
 	else {
 		palloc.tail = p;
-		p->next = 0;
+		p->next = nil;
 	}
 	palloc.head = p;
-	p->prev = 0;
+	p->prev = nil;
 	palloc.freecount++;
 }
 
@@ -234,7 +234,7 @@ newpage(int clear, Segment *s, uintptr va, int locked)
 			break;
 
 	ct = PG_NOFLUSH;
-	if(p == 0) {
+	if(p == nil) {
 		p = palloc.head;
 		p->color = color;
 		ct = PG_NEWCOL;
@@ -290,7 +290,7 @@ putpage(Page *p)
 	else
 		pagechainhead(p);
 
-	if(palloc.r.p != 0)
+	if(palloc.r.p != nil)
 		wakeup(&palloc.r);
 
 	unlock(p);
@@ -307,7 +307,7 @@ auxpage(void)
 	if(palloc.freecount <= highwater) {
 		/* memory's tight, don't use it for file cache */
 		unlock(&palloc);
-		return 0;
+		return nil;
 	}
 	pageunchain(p);
 
@@ -383,7 +383,7 @@ retry:
 			break;
 
 	/* No page of the correct color */
-	if(np == 0) {
+	if(np == nil) {
 		unlock(&palloc);
 		uncachepage(p);
 		return 1;
@@ -437,12 +437,12 @@ uncachepage(Page *p)			/* Always called with a locked page */
 {
 	Page **l, *f;
 
-	if(p->image == 0)
+	if(p->image == nil)
 		return;
 
 	lock(&palloc.hashlock);
 	l = &pghash(p->daddr);
-	for(f = *l; f; f = f->hash) {
+	for(f = *l; f != nil; f = f->hash) {
 		if(f == p) {
 			*l = p->hash;
 			break;
@@ -451,7 +451,7 @@ uncachepage(Page *p)			/* Always called with a locked page */
 	}
 	unlock(&palloc.hashlock);
 	putimage(p->image);
-	p->image = 0;
+	p->image = nil;
 	p->daddr = 0;
 }
 
@@ -484,13 +484,13 @@ cachedel(Image *i, ulong daddr)
 
 	lock(&palloc.hashlock);
 	l = &pghash(daddr);
-	for(f = *l; f; f = f->hash) {
+	for(f = *l; f != nil; f = f->hash) {
 		if(f->image == i && f->daddr == daddr) {
 			lock(f);
 			if(f->image == i && f->daddr == daddr){
 				*l = f->hash;
 				putimage(f->image);
-				f->image = 0;
+				f->image = nil;
 				f->daddr = 0;
 			}
 			unlock(f);
@@ -507,7 +507,7 @@ lookpage(Image *i, ulong daddr)
 	Page *f;
 
 	lock(&palloc.hashlock);
-	for(f = pghash(daddr); f; f = f->hash) {
+	for(f = pghash(daddr); f != nil; f = f->hash) {
 		if(f->image == i && f->daddr == daddr) {
 			unlock(&palloc.hashlock);
 
@@ -528,7 +528,7 @@ lookpage(Image *i, ulong daddr)
 	}
 	unlock(&palloc.hashlock);
 
-	return 0;
+	return nil;
 }
 
 uvlong
@@ -545,7 +545,7 @@ pagereclaim(int npages)
 	 * end of the list (see putpage) so start there and work
 	 * backward.
 	 */
-	for(p = palloc.tail; p && p->image && npages > 0; p = p->prev) {
+	for(p = palloc.tail; p != nil && p->image != nil && npages > 0; p = p->prev) {
 		if(p->ref == 0 && canlock(p)) {
 			if(p->ref == 0) {
 				npages--;
@@ -608,16 +608,16 @@ freepte(Segment *s, Pte *p)
 		ptop = &p->pages[PTEPERTAB];
 		if(fn) {
 			for(pg = p->pages; pg < ptop; pg++) {
-				if(*pg == 0)
+				if(*pg == nil)
 					continue;
 				(*fn)(*pg);
-				*pg = 0;
+				*pg = nil;
 			}
 			break;
 		}
 		for(pg = p->pages; pg < ptop; pg++) {
 			pt = *pg;
-			if(pt == 0)
+			if(pt == nil)
 				continue;
 			lock(pt);
 			ref = --pt->ref;
@@ -628,9 +628,9 @@ freepte(Segment *s, Pte *p)
 		break;
 	default:
 		for(pg = p->first; pg <= p->last; pg++)
-			if(*pg) {
+			if(*pg != nil) {
 				putpage(*pg);
-				*pg = 0;
+				*pg = nil;
 			}
 	}
 	free(p);
--- /sys/src/9k/port/proc.c
+++ /sys/src/9k/port/proc.c
@@ -70,7 +70,7 @@ schedinit(void)		/* never returns */
 		if((e = up->edf) && (e->flags & Admitted))
 			edfrecord(up);
 		updatecpu(up);
-		m->proc = 0;
+		m->proc = nil;
 		switch(up->state) {
 		case Running:
 			ready(up);
@@ -159,7 +159,7 @@ sched(void)
 	}
 	if(p != m->readied)
 		m->schedticks = m->ticks + HZ/10;
-	m->readied = 0;
+	m->readied = nil;
 	up = p;
 	up->state = Running;
 	up->mach = m;
@@ -373,11 +373,11 @@ dequeueproc(Schedq *rq, Proc *tp)
 	/*
 	 *  p->mach==0 only when process state is saved
 	 */
-	if(p == 0 || p->mach){
+	if(p == nil || p->mach){
 		unlock(runq);
 		return nil;
 	}
-	if(p->rnext == 0)
+	if(p->rnext == nil)
 		rq->tail = l;
 	if(l)
 		l->rnext = p->rnext;
@@ -584,16 +584,16 @@ newproc(void)
 
 	p->state = Scheding;
 	p->psstate = "New";
-	p->mach = 0;
-	p->qnext = 0;
+	p->mach = nil;
+	p->qnext = nil;
 	p->nchild = 0;
 	p->nwait = 0;
-	p->waitq = 0;
-	p->parent = 0;
-	p->pgrp = 0;
-	p->egrp = 0;
-	p->fgrp = 0;
-	p->rgrp = 0;
+	p->waitq = nil;
+	p->parent = nil;
+	p->pgrp = nil;
+	p->egrp = nil;
+	p->fgrp = nil;
+	p->rgrp = nil;
 	p->pdbg = 0;
 	p->kp = 0;
 	if(up != nil && up->procctl == Proc_tracesyscall)
@@ -602,7 +602,7 @@ newproc(void)
 		p->procctl = 0;
 	p->syscalltrace = nil;
 	p->notepending = 0;
-	p->ureg = 0;
+	p->ureg = nil;
 	p->privatemem = 0;
 	p->errstr = p->errbuf0;
 	p->syserrstr = p->errbuf1;
@@ -622,12 +622,12 @@ newproc(void)
 	p->noteid = incref(&noteidalloc);
 	if(p->pid <= 0 || p->noteid <= 0)
 		panic("pidalloc");
-	if(p->kstack == 0)
+	if(p->kstack == nil)
 		p->kstack = smalloc(KSTACK);
 
 	/* sched params */
-	p->mp = 0;
-	p->wired = 0;
+	p->mp = nil;
+	p->wired = nil;
 	procpriority(p, PriNormal, 0);
 	p->cpu = 0;
 	p->lastupdate = sys->ticks*Scaling;
@@ -650,7 +650,7 @@ procwired(Proc *p, int bm)
 	if(bm < 0){
 		/* pick a machine to wire to */
 		memset(nwired, 0, sizeof(nwired));
-		p->wired = 0;
+		p->wired = nil;
 		for(i=0; (pp = psincref(i)) != nil; i++){
 			wm = pp->wired;
 			if(wm && pp->pid)
@@ -871,7 +871,7 @@ postnote(Proc *p, int dolock, char *n, int flag)
 	if(dolock)
 		qlock(&p->debug);
 
-	if(flag != NUser && (p->notify == 0 || p->notified))
+	if(flag != NUser && (p->notify == nil || p->notified))
 		p->nnote = 0;
 
 	ret = 0;
@@ -1051,8 +1051,8 @@ pexit(char *exitstr, int freemem)
 	 */
 	if(up->kp == 0) {
 		p = up->parent;
-		if(p == 0) {
-			if(exitstr == 0)
+		if(p == nil) {
+			if(exitstr == nil)
 				exitstr = "unknown";
 			panic("boot process died: %s", exitstr);
 		}
@@ -1136,7 +1136,7 @@ pexit(char *exitstr, int freemem)
 	qunlock(&up->debug);
 
 	edfstop(up);
-	if(up->edf){
+	if(up->edf != nil){
 		free(up->edf);
 		up->edf = nil;
 	}
@@ -1174,7 +1174,7 @@ pwait(Waitmsg *w)
 	}
 
 	lock(&up->exl);
-	if(up->nchild == 0 && up->waitq == 0) {
+	if(up->nchild == 0 && up->waitq == nil) {
 		unlock(&up->exl);
 		error(Enochild);
 	}
@@ -1205,7 +1205,7 @@ dumpaproc(Proc *p)
 	uintptr bss;
 	char *s;
 
-	if(p == 0)
+	if(p == nil)
 		return;
 
 	bss = 0;
@@ -1213,7 +1213,7 @@ dumpaproc(Proc *p)
 		bss = p->seg[BSEG]->top;
 
 	s = p->psstate;
-	if(s == 0)
+	if(s == nil)
 		s = statename[p->state];
 	print("%3d:%10s pc %#p dbgpc %#p  %8s (%s) ut %ld st %ld bss %#p qpc %#p nl %d nd %lud lpc %#p pri %lud\n",
 		p->pid, p->text, p->pc, dbgpc(p), s, statename[p->state],
@@ -1227,7 +1227,7 @@ procdump(void)
 	int i;
 	Proc *p;
 
-	if(up)
+	if(up != nil)
 		print("up %d\n", up->pid);
 	else
 		print("no current process\n");
@@ -1333,8 +1333,8 @@ kproc(char *name, void (*func)(void *), void *arg)
 	p->notified = 0;
 	p->lastnote = up->lastnote;
 	p->notify = up->notify;
-	p->ureg = 0;
-	p->dbgreg = 0;
+	p->ureg = nil;
+	p->dbgreg = nil;
 
 	procpriority(p, PriKproc, 0);
 
@@ -1342,7 +1342,7 @@ kproc(char *name, void (*func)(void *), void *arg)
 
 	kstrdup(&p->user, eve);
 	kstrdup(&p->text, name);
-	if(kpgrp == 0)
+	if(kpgrp == nil)
 		kpgrp = newpgrp();
 	p->pgrp = kpgrp;
 	incref(kpgrp);
@@ -1442,7 +1442,7 @@ killbig(char *why)
 		l = 0;
 		for(i=1; i<NSEG; i++) {
 			s = p->seg[i];
-			if(s != nil)
+			if(s != 0)
 				l += s->top - s->base;
 		}
 		if(l > max && ((p->procmode&0222) || strcmp(eve, p->user)!=0)) {
@@ -1507,7 +1507,7 @@ accounttime(void)
 	static ulong nrun;
 
 	p = m->proc;
-	if(p) {
+	if(p != nil) {
 		nrun++;
 		p->time[p->insyscall]++;
 	}
--- /sys/src/9k/port/segment.c
+++ /sys/src/9k/port/segment.c
@@ -52,11 +52,11 @@ putseg(Segment *s)
 	Pte **pp, **emap;
 	Image *i;
 
-	if(s == 0)
+	if(s == nil)
 		return;
 
 	i = s->image;
-	if(i != 0) {
+	if(i != nil) {
 		lock(i);
 		lock(s);
 		if(i->s == s && s->ref == 1)
@@ -79,13 +79,13 @@ putseg(Segment *s)
 
 	emap = &s->map[s->mapsize];
 	for(pp = s->map; pp < emap; pp++)
-		if(*pp)
+		if(*pp != nil)
 			freepte(s, *pp);
 
 	qunlock(&s->lk);
 	if(s->map != s->ssegmap)
 		free(s->map);
-	if(s->profile != 0)
+	if(s->profile != nil)
 		free(s->profile);
 	free(s);
 }
@@ -158,7 +158,7 @@ dupseg(Segment **seg, int segno, int share)
 	}
 	size = s->mapsize;
 	for(i = 0; i < size; i++)
-		if(pte = s->map[i])
+		if((pte = s->map[i]) != nil)
 			n->map[i] = ptecpy(pte);
 
 	n->flushme = s->flushme;
@@ -268,7 +268,7 @@ isoverlap(Proc* p, uintptr va, usize len)
 	newtop = va+len;
 	for(i = 0; i < NSEG; i++) {
 		ns = p->seg[i];
-		if(ns == 0)
+		if(ns == nil)
 			continue;
 		if(newtop > ns->base && va < ns->top)
 			return ns;
@@ -282,7 +282,7 @@ segclock(uintptr pc)
 	Segment *s;
 
 	s = up->seg[TSEG];
-	if(s == 0 || s->profile == 0)
+	if(s == nil || s->profile == nil)
 		return;
 
 	s->profile[0] += TK2MS(1);
--- /sys/src/9k/port/sysproc.c
+++ /sys/src/9k/port/sysproc.c
@@ -113,7 +113,7 @@ sysrfork(Ar0* ar0, va_list list)
 		nexterror();
 	}
 	for(i = 0; i < NSEG; i++)
-		if(up->seg[i])
+		if(up->seg[i] != nil)
 			p->seg[i] = dupseg(up->seg, i, n);
 	qunlock(&p->seglock);
 	poperror();
@@ -200,7 +200,7 @@ sysrfork(Ar0* ar0, va_list list)
 	p->fixedpri = up->fixedpri;
 	p->mp = up->mp;
 	wm = up->wired;
-	if(wm)
+	if(wm != nil)
 		procwired(p, wm->machno);
 	if(p->trace && (pt = proctrace) != nil){
 		strncpy((char*)&ptarg, p->text, sizeof ptarg);
--- /sys/src/9k/port/sysseg.c
+++ /sys/src/9k/port/sysseg.c
@@ -65,7 +65,7 @@ ibrk(uintptr addr, int seg)
 	Pte **map;
 
 	s = up->seg[seg];
-	if(s == 0)
+	if(s == nil)
 		error(Ebadarg);
 
 	if(addr == 0)
@@ -79,7 +79,7 @@ ibrk(uintptr addr, int seg)
 
 	/* We may start with the bss overlapping the data */
 	if(addr < s->base) {
-		if(seg != BSEG || up->seg[DSEG] == 0 || addr < up->seg[DSEG]->base)
+		if(seg != BSEG || up->seg[DSEG] == nil || addr < up->seg[DSEG]->base)
 			error(Enovmem);
 		addr = s->base;
 	}
@@ -106,7 +106,7 @@ ibrk(uintptr addr, int seg)
 
 	for(i = 0; i < NSEG; i++) {
 		ns = up->seg[i];
-		if(ns == 0 || ns == s)
+		if(ns == nil || ns == s)
 			continue;
 		if(newtop > ns->base && s->base < ns->top)
 			error(Esoverlap);
--- /sys/src/9k/boot/bootauth.c
+++ /sys/src/9k/boot/bootauth.c
@@ -39,7 +39,7 @@ authentication(int cpuflag)
 		av[ac++] = "-a";
 		av[ac++] = authaddr;
 	}
-	av[ac] = 0;
+	av[ac] = nil;
 	switch(fork()){
 	case -1:
 		fatal("starting factotum");