diff --git a/README.md b/README.md
index 39db55a..fe43985 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,4 @@
-# common
\ No newline at end of file
+# common
+
+* master: [![Build Status](https://travis-ci.org/c64lib/common.svg?branch=master)](https://travis-ci.org/c64lib/common)
+* develop: [![Build Status](https://travis-ci.org/c64lib/common.svg?branch=develop)](https://travis-ci.org/c64lib/common)
diff --git a/common.asm b/common.asm
index 81b91bd..7716269 100644
--- a/common.asm
+++ b/common.asm
@@ -8,7 +8,7 @@
  * value: byte to be negated
  */
 .function neg(value) {
-	.return value ^ $FF
+  .return value ^ $FF
 }
 .assert "neg($00) gives $FF", neg($00), $FF
 .assert "neg($FF) gives $00", neg($FF), $00
diff --git a/mem.asm b/mem.asm
index eda3128..ae4eb68 100644
--- a/mem.asm
+++ b/mem.asm
@@ -1,95 +1,105 @@
 #importonce
 .filenamespace c64lib
 
+/*
+ * MOS 650X Vector table constants.
+ */
+.label NMI_LO       = $FFFA
+.label NMI_HI       = $FFFB
+.label RESET_LO     = $FFFC
+.label RESET_HI     = $FFFD
+.label IRQ_LO       = $FFFE
+.label IRQ_HI       = $FFFF
+
 /*
  * Adds 16 bit number "value" to given memory cell specified by "low" address.
  *
  * MOD: A, C
  */
 .macro add16(value, low) {
-	clc
-	lda low
-	adc #<value
-	sta low
-	lda low + 1
-	adc #>value
-	sta low + 1
+  clc
+  lda low
+  adc #<value
+  sta low
+  lda low + 1
+  adc #>value
+  sta low + 1
 }
 .assert "add16($0102, $A000)", { :add16($0102, $A000) }, {
-	clc; lda $A000; adc #$02; sta $A000
-	lda $A001; adc #$01; sta $A001
+  clc; lda $A000; adc #$02; sta $A000
+  lda $A001; adc #$01; sta $A001
 }
-				
+        
 /*
  * Subtracts 16 bit number "value" from given memory cell specified by "low" address.
  *
  * MOD: A, C
  */
 .macro sub16(value, low) {
-	sec
-	lda low
-	sbc	#<value
-	sta low
-	lda low + 1
-	sbc #>value
-	sta low + 1
+  sec
+  lda low
+  sbc #<value
+  sta low
+  lda low + 1
+  sbc #>value
+  sta low + 1
 }
 .assert "sub16($0102, $A000)", { :sub16($0102, $A000) }, {
-	sec; lda $A000; sbc #$02; sta $A000
-	lda $A001; sbc #$01; sta $A001
+  sec; lda $A000; sbc #$02; sta $A000
+  lda $A001; sbc #$01; sta $A001
 }
-	
+  
 /*
  * Adds value from "source" memory location to value in "destination" memory location.
  *
  * MOD: A, C
  */
 .macro addMem16(source, destination) {
-	clc
-	lda source
-	adc destination
-	sta destination
-	lda source + 1
-	adc destination + 1
-	sta destination + 1
+  clc
+  lda source
+  adc destination
+  sta destination
+  lda source + 1
+  adc destination + 1
+  sta destination + 1
 }
 .assert "addMem16($A000, $B000)", { :addMem16($A000, $B000) }, {
-	clc; lda $A000; adc $B000; sta $B000
-	lda $A001; adc $B001; sta $B001
+  clc; lda $A000; adc $B000; sta $B000
+  lda $A001; adc $B001; sta $B001
 }
-				
+        
 /*
  * Subtracts value from "source" memory location from value in "destination" memory location.
  *
  * MOD: A, C
  */
-.macro subMem16(source, destination) {			
-	sec
-	lda destination
-	sbc source
-	sta destination
-	lda destination + 1
-	sbc source + 1
-	sta destination + 1
+.macro subMem16(source, destination) {      
+  sec
+  lda destination
+  sbc source
+  sta destination
+  lda destination + 1
+  sbc source + 1
+  sta destination + 1
 }
 .assert "subMem16($A000, $B000)", { :subMem16($A000, $B000) }, {
-	sec; lda $B000; sbc $A000; sta $B000
-	lda $B001; sbc $A001; sta $B001
+  sec; lda $B000; sbc $A000; sta $B000
+  lda $B001; sbc $A001; sta $B001
 }
-				
+        
 /*
  * Shifts left 2 byte number specified with "low" address. Carry flag indicates last bit that has been "shifted out".
  * 
  * MOD: A, C
  */
 .macro asl16(low) {
-	clc
-	asl low
-	bcc !+
-	lda low + 1
-	asl
-	ora #%1
-	sta low + 1
+  clc
+  asl low
+  bcc !+
+  lda low + 1
+  asl
+  ora #%1
+  sta low + 1
 !:
 }
 
@@ -99,18 +109,18 @@
  * MOD: A
  */
 .macro copyFast(source, destination, count) {
-	.for(var i = 0; i < count; i++) {
-		lda source + i
-		sta destination + i
-	}
+  .for(var i = 0; i < count; i++) {
+    lda source + i
+    sta destination + i
+  }
 }
 .assert "copyFast($A000, $B000, 0) copies nothing", { :copyFast($A000, $B000, 0) }, {}
 .assert "copyFast($A000, $B000, 1) copies one byte", { :copyFast($A000, $B000, 1) }, {
-	lda $A000; sta $B000
+  lda $A000; sta $B000
 }
 .assert "copyFast($A000, $B000, 2) copies two bytes", { :copyFast($A000, $B000, 2) }, {
-	lda $A000; sta $B000
-	lda $A001; sta $B001
+  lda $A000; sta $B000
+  lda $A001; sta $B001
 }
 
 /*
@@ -119,15 +129,15 @@
  * MOD: A, X
  */
 .macro fillScreen(address, value) {
-	lda #value
-	ldx #$00
+  lda #value
+  ldx #$00
 loop:
-	sta address, x
-	sta address + $0100, x
-	sta address + $0200, x
-	sta address + $0300, x
-	inx
-	bne loop
+  sta address, x
+  sta address + $0100, x
+  sta address + $0200, x
+  sta address + $0300, x
+  inx
+  bne loop
 }
 
 /*
@@ -136,9 +146,9 @@ loop:
  * MOD: -
  */
 .macro inc16(destination) {
-	inc destination
-	bne !+
-	inc destination + 1
+  inc destination
+  bne !+
+  inc destination + 1
 !:
 }
 
@@ -148,8 +158,8 @@ loop:
  * MOD: A
  */
 .macro set8(value, mem) {
-	lda #value
-	sta mem
+  lda #value
+  sta mem
 }
 
 /*
@@ -158,22 +168,22 @@ loop:
  * MOD: A
  */
 .macro set16(value, mem) {
-	:set8(<value, mem)
-	:set8(>value, mem + 1)
+  :set8(<value, mem)
+  :set8(>value, mem + 1)
 }
 .assert "set16($1234, $A000) stores $34 under $A000 and $12 under $A001", { :set16($3412, $A000) }, {
-	lda #$12
-	sta $A000
-	lda #$34
-	sta $A001
+  lda #$12
+  sta $A000
+  lda #$34
+  sta $A001
 }
 
 .macro copyWordIndirect(source, destinationPointer) {
-	ldy #0
-	lda source
-	sta (destinationPointer), y
-	iny
-	lda source + 1
-	sta (destinationPointer), y
-}
-							
+  ldy #0
+  lda source
+  sta (destinationPointer), y
+  iny
+  lda source + 1
+  sta (destinationPointer), y
+}
+