--- a/src/ANN.cpp
+++ b/src/ANN.cpp
@@ -48,9 +48,9 @@ ANNdist annDist(						// interpoint squared distance
 	ANNpoint			p,
 	ANNpoint			q)
 {
-	register int d;
-	register ANNcoord diff;
-	register ANNcoord dist;
+	int d;
+	ANNcoord diff;
+	ANNcoord dist;
 
 	dist = 0;
 	for (d = 0; d < dim; d++) {
--- a/src/kd_fix_rad_search.cpp
+++ b/src/kd_fix_rad_search.cpp
@@ -147,11 +147,11 @@ void ANNkd_split::ann_FR_search(ANNdist box_dist)
 
 void ANNkd_leaf::ann_FR_search(ANNdist box_dist)
 {
-	register ANNdist dist;				// distance to data point
-	register ANNcoord* pp;				// data coordinate pointer
-	register ANNcoord* qq;				// query coordinate pointer
-	register ANNcoord t;
-	register int d;
+	ANNdist dist;				// distance to data point
+	ANNcoord* pp;				// data coordinate pointer
+	ANNcoord* qq;				// query coordinate pointer
+	ANNcoord t;
+	int d;
 
 	for (int i = 0; i < n_pts; i++) {	// check points in bucket
 
--- a/src/kd_pr_search.cpp
+++ b/src/kd_pr_search.cpp
@@ -180,12 +180,12 @@ void ANNkd_split::ann_pri_search(ANNdist box_dist)
 
 void ANNkd_leaf::ann_pri_search(ANNdist box_dist)
 {
-	register ANNdist dist;				// distance to data point
-	register ANNcoord* pp;				// data coordinate pointer
-	register ANNcoord* qq;				// query coordinate pointer
-	register ANNdist min_dist;			// distance to k-th closest point
-	register ANNcoord t;
-	register int d;
+	ANNdist dist;				// distance to data point
+	ANNcoord* pp;				// data coordinate pointer
+	ANNcoord* qq;				// query coordinate pointer
+	ANNdist min_dist;			// distance to k-th closest point
+	ANNcoord t;
+	int d;
 
 	min_dist = ANNprPointMK->max_key(); // k-th smallest distance so far
 
--- a/src/kd_search.cpp
+++ b/src/kd_search.cpp
@@ -171,12 +171,12 @@ void ANNkd_split::ann_search(ANNdist box_dist)
 
 void ANNkd_leaf::ann_search(ANNdist box_dist)
 {
-	register ANNdist dist;				// distance to data point
-	register ANNcoord* pp;				// data coordinate pointer
-	register ANNcoord* qq;				// query coordinate pointer
-	register ANNdist min_dist;			// distance to k-th closest point
-	register ANNcoord t;
-	register int d;
+	ANNdist dist;				// distance to data point
+	ANNcoord* pp;				// data coordinate pointer
+	ANNcoord* qq;				// query coordinate pointer
+	ANNdist min_dist;			// distance to k-th closest point
+	ANNcoord t;
+	int d;
 
 	min_dist = ANNkdPointMK->max_key(); // k-th smallest distance so far
 
--- a/src/kd_util.cpp
+++ b/src/kd_util.cpp
@@ -127,10 +127,10 @@ ANNdist annBoxDistance(			// compute distance from point to box
 	const ANNpoint		hi,				// high point of box
 	int					dim)			// dimension of space
 {
-	register ANNdist dist = 0.0;		// sum of squared distances
-	register ANNdist t;
+	ANNdist dist = 0.0;		// sum of squared distances
+	ANNdist t;
 
-	for (register int d = 0; d < dim; d++) {
+	for (int d = 0; d < dim; d++) {
 		if (q[d] < lo[d]) {				// q is left of box
 			t = ANNdist(lo[d]) - ANNdist(q[d]);
 			dist = ANN_SUM(dist, ANN_POW(t));
@@ -238,8 +238,8 @@ void annMedianSplit(
 	int l = 0;							// left end of current subarray
 	int r = n-1;						// right end of current subarray
 	while (l < r) {
-		register int i = (r+l)/2;		// select middle as pivot
-		register int k;
+		int i = (r+l)/2;		// select middle as pivot
+		int k;
 
 		if (PA(i,d) > PA(r,d))			// make sure last > pivot
 			PASWAP(i,r)
--- a/src/pr_queue.h
+++ b/src/pr_queue.h
@@ -86,9 +86,9 @@ public:
 		PQinfo inf)						// item info
 		{
 			if (++n > max_size) annError("Priority queue overflow.", ANNabort);
-			register int r = n;
+			int r = n;
 			while (r > 1) {				// sift up new item
-				register int p = r/2;
+				int p = r/2;
 				ANN_FLOP(1)				// increment floating ops
 				if (pq[p].key <= kv)	// in proper order
 					break;
@@ -105,9 +105,9 @@ public:
 		{
 			kv = pq[1].key;				// key of min item
 			inf = pq[1].info;			// information of min item
-			register PQkey kn = pq[n--].key;// last item in queue
-			register int p = 1;			// p points to item out of position
-			register int r = p<<1;		// left child of p
+			PQkey kn = pq[n--].key;// last item in queue
+			int p = 1;			// p points to item out of position
+			int r = p<<1;		// left child of p
 			while (r <= n) {			// while r is still within the heap
 				ANN_FLOP(2)				// increment floating ops
 										// set r to smaller child of p
--- a/src/pr_queue_k.h
+++ b/src/pr_queue_k.h
@@ -100,7 +100,7 @@ public:
 		PQKkey kv,						// key value
 		PQKinfo inf)					// item info
 		{
-			register int i;
+			int i;
 										// slide larger values up
 			for (i = n; i > 0; i--) {
 				if (mk[i-1].key > kv)