diff --git a/src/inc/fpu.plh b/src/inc/fpu.plh
index 5fcb8e7..ee8c9c2 100644
--- a/src/inc/fpu.plh
+++ b/src/inc/fpu.plh
@@ -1,42 +1,54 @@
 import fpu
+//
+// RPN Register indeces
+//
+const X_REG = 0
+const Y_REG = 1
+const Z_REG = 2
+const T_REG = 3
+//
+// FPU API
+//
 struc t_fpu
-word reset
-word pushDbl
-word pushDbl
-word pushDbl
-word pushExt
-word pushStr
-word pullDbl
-word pullDbl
-word pullDbl
-word pullExt
-word pullStr
-word loadDbl
-word loadDbl
-word loadDbl
-word loadExt
-word loadStr
-word storDbl
-word storDbl
-word storDbl
-word storExt
-word storStr
-word shiftUp
-word shiftDown
-word rotateUp
-word rotateDown
-word dup
-word swap
-word clear
-word add
-word sub
-word mul
-word div
-word rem
-word neg
-word abs
-word trunc
-word round
-word sqrt
+    word reset
+    word constPi
+    word constE
+    word pushDbl
+    word pushDbl
+    word pushDbl
+    word pushExt
+    word pushStr
+    word pullDbl
+    word pullDbl
+    word pullDbl
+    word pullExt
+    word pullStr
+    word loadDbl
+    word loadDbl
+    word loadDbl
+    word loadExt
+    word loadStr
+    word storDbl
+    word storDbl
+    word storDbl
+    word storExt
+    word storStr
+    word shiftUp
+    word shiftDown
+    word rotateUp
+    word rotateDown
+    word dup
+    word swap
+    word clear
+    word add
+    word sub
+    word mul
+    word div
+    word rem
+    word neg
+    word abs
+    word trunc
+    word round
+    word sqrt
 end
 end
diff --git a/src/libsrc/fpu.pla b/src/libsrc/fpu.pla
index efa7f04..03368cb 100644
--- a/src/libsrc/fpu.pla
+++ b/src/libsrc/fpu.pla
@@ -7,14 +7,15 @@ include "inc/fpstr.plh"
 //
 // External interface to FPU library
 //
-predef reset, pushInt, pushSgl, pushDbl, pushExt, pushStr
+predef reset, constPi, constE
+predef        pushInt, pushSgl, pushDbl, pushExt, pushStr
 predef        pullInt, pullSgl, pullDbl, pullExt, pullStr
 predef        loadInt, loadSgl, loadDbl, loadExt, loadStr
 predef        storInt, storSgl, storDbl, storExt, storStr
 predef        shiftUp, shiftDown, rotateUp, rotateDown, dup, swap, clear
 predef        add, sub, mul, div, rem
 predef        neg, abs, trunc, round, sqrt, square
-export word fpu = @reset
+export word fpu = @reset, @constPi, @constE
 word = @pushInt, @pushSgl, @pushDbl, @pushExt, @pushStr
 word = @pullInt, @pullSgl, @pullDbl, @pullExt, @pullStr
 word = @loadInt, @loadSgl, @loadDbl, @loadExt, @loadStr
@@ -23,6 +24,11 @@ word = @shiftUp, @shiftDown, @rotateUp, @rotateDown, @dup, @swap, @clear
 word = @add, @sub, @mul, @div, @rem
 word = @neg, @abs, @trunc, @round, @sqrt, @square
 //
+// Useful constants
+//
+byte ext_pi[t_extended] = $35,$C2,$68,$21,$A2,$DA,$0F,$C9,$00,$40
+byte ext_e[t_extended]  = $9B,$4A,$BB,$A2,$5B,$54,$F8,$AD,$00,$40
+//
 // FP Stack
 //
 byte stack[t_extended*4]
@@ -234,6 +240,15 @@ def square
     sane:zpRestore()
 end
 //
+// Push useful constants
+//
+def constPi
+    return pushExt(@ext_pi)
+end
+def constE
+    return pushExt(@ext_e)
+end
+//
 // Reset FPU and SANE
 //
 def reset
@@ -261,6 +276,16 @@ def dumpStack#0
         puts("  "); puti(r); putc(':'); puts(@regStr); putln
     next
 end
+def dumpExt#0
+    byte i
+
+    for i = 0 to t_extended-1
+        putc('$')
+        call($FDDA, stackRegs.[0, i], 0, 0, 0)
+        putc(' ')
+    next
+    putln
+end
 //
 // Run through some test cases
 //
@@ -281,4 +306,12 @@ dumpStack
 puts("Sqrt\n")
 sqrt
 dumpStack
+pushStr("2.71828182845904523536028747")
+dumpExt
+constE
+dumpExt
+pushStr("3.14159265358979323846264338")
+dumpExt
+constPi
+dumpExt
 done