diff --git a/src/inc/fpstr.plh b/src/inc/fpstr.plh
index 48465ca..02eecb1 100644
--- a/src/inc/fpstr.plh
+++ b/src/inc/fpstr.plh
@@ -1,10 +1,17 @@
 import fpstr
 //
+// String formatting bits
+//
+const FPSTR_FIXED = 1 // Fixed count of fractional digits
+const FPSTR_FLOAT = 0 // Floating count of fractional digits
+const FPSTR_STRIP = 2 // Strip trailing fractional zeros
+const FPSTR_EXP   = 4 // Force exponential format
+//
 // Parse string into decrecord, return SANE conversion output
 //
 predef str2ext(str, ext)#1
 //
 // Convert extended FP to string using , return string
 //
-predef ext2str(ext, str, numdigits, expformat)#1
+predef ext2str(ext, str, intdigits, fracdigits, format)#1
 end
diff --git a/src/libsrc/fpstr.pla b/src/libsrc/fpstr.pla
index 461d6ca..423984f 100644
--- a/src/libsrc/fpstr.pla
+++ b/src/libsrc/fpstr.pla
@@ -129,14 +129,15 @@ end
 //
 // Convert extended FP to string using , return string
 //
-export def ext2str(ext, str, numdigits, expformat)
-    byte d, i, sigdigits
+export def ext2str(ext, str, intdigits, fracdigits, format)
+    byte d, i, sigdigits, numdigits
     word dp, tens
     byte decform[t_decformat]
     byte decrec[t_decrecord]
 
-    decform:style  = 0
-    decform:digits = numdigits
+    numdigits = intdigits + fracdigits
+    decform:style  = format & $01
+    decform:digits = decform:style ?? fracdigits :: numdigits
     sane:fpOp3(FFEXT|FOB2D, @decrec, ext, @decform)
     ^(str+1) = decrec.sgn ?? '-' :: ' '
     if decrec.sig.1 == 'I'
@@ -154,19 +155,24 @@ export def ext2str(ext, str, numdigits, expformat)
         return str
     fin
     if decrec.sig.1 == '0'
+        while decrec.sig < fracdigits
+            decrec.sig++
+            decrec.sig[decrec.sig] = '0'
+        loop
         decrec:exp = -decrec.sig
     fin
     dp = decrec.sig + decrec:exp
     sigdigits = decrec.sig
-    if decrec:exp < 0
+    if decrec:exp < 0 and format & $02
         //
         // Strip off trailing fractional zeros
         //
         while sigdigits > dp and decrec.sig[sigdigits] == '0'
             sigdigits--
+            decrec:exp++
         loop
     fin
-    if (decrec:exp + (decrec.sig - sigdigits)) < -numdigits or decrec:exp > 0 or expformat
+    if sigdigits - decrec:exp > numdigits or decrec:exp > 0 or format & $04
         //
         // Convert to exponential format
         //
diff --git a/src/libsrc/fpu.pla b/src/libsrc/fpu.pla
index 9f3d5cf..efa7f04 100644
--- a/src/libsrc/fpu.pla
+++ b/src/libsrc/fpu.pla
@@ -42,7 +42,7 @@ def shiftUp
 end
 def shiftDown
     stackRegs[0], stackRegs[1], stackRegs[2], stackRegs[3] = stackRegs[1], stackRegs[2], stackRegs[3], stackRegs[0]
-    memset(stackRegs[3], 0, t_extended)
+    memcpy(stackRegs[3], stackRegs[2], t_extended)
 end
 def dup
     stackRegs[0], stackRegs[1], stackRegs[2], stackRegs[3] = stackRegs[3], stackRegs[0], stackRegs[1], stackRegs[2]
@@ -154,9 +154,9 @@ def pushStr(pStr)
     str2ext(pStr, stackRegs[0])
     return sane:zpRestore()
 end
-def pullStr(pStr, sigdigits, expformat)
+def pullStr(pStr, intdigits, fracdigits, format)
     sane:zpSave()
-    ext2str(stackRegs[0], pStr, sigdigits, expformat)
+    ext2str(stackRegs[0], pStr, intdigits, fracdigits, format)
     sane:zpRestore()
     return shiftDown
 end
@@ -165,9 +165,9 @@ def loadStr(pStr, reg)
     str2ext(pStr, stackRegs[reg])
     return sane:zpRestore()
 end
-def storStr(pStr, sigdigits, expformat, reg)
+def storStr(pStr, intdigits, fracdigits, format, reg)
     sane:zpSave()
-    ext2str(stackRegs[reg], pStr, sigdigits, expformat)
+    ext2str(stackRegs[reg], pStr, intdigits, fracdigits, format)
     return sane:zpRestore()
 end
 //
@@ -254,10 +254,10 @@ end
 //
 def dumpStack#0
     byte r
-    byte regStr[24]
+    byte regStr[16]
 
     for r = 3 downto 0
-        storStr(@regStr, 8, 0, r)
+        storStr(@regStr, 6, 4, 1, r)
         puts("  "); puti(r); putc(':'); puts(@regStr); putln
     next
 end
diff --git a/src/samplesrc/sanity.pla b/src/samplesrc/sanity.pla
index 26a0568..bc558bc 100644
--- a/src/samplesrc/sanity.pla
+++ b/src/samplesrc/sanity.pla
@@ -131,14 +131,15 @@ def str2ext(str, ext)
     //putc(decrec.sgn ?? '-' :: '+'); puts(@decrec.sig); putc('e'); puti(decrec:exp); putln
     return sane:fpOp2(FFEXT|FOD2B, ext, @decrec)
 end
-def ext2str(ext, str, numdigits, expformat)
-    byte d, i, sigdigits
+def ext2str(ext, str, intdigits, fracdigits, format)
+    byte d, i, sigdigits, numdigits
     word dp, tens
     byte decform[t_decformat]
     byte decrec[t_decrecord]
 
-    decform:style  = 0
-    decform:digits = numdigits
+    numdigits = intdigits + fracdigits
+    decform:style  = format & $01
+    decform:digits = decform:style ?? fracdigits :: numdigits
     sane:fpOp3(FFEXT|FOB2D, @decrec, ext, @decform)
     ^(str+1) = decrec.sgn ?? '-' :: ' '
     if decrec.sig.1 == 'I'
@@ -156,21 +157,28 @@ def ext2str(ext, str, numdigits, expformat)
         return str
     fin
     if decrec.sig.1 == '0'
+        while decrec.sig < fracdigits
+            decrec.sig++
+            decrec.sig[decrec.sig] = '0'
+        loop
         decrec:exp = -decrec.sig
     fin
     dp = decrec.sig + decrec:exp
     sigdigits = decrec.sig
-    //putc(decrec.sgn ?? '-' :: '+'); puts(@decrec.sig); putc('e'); puti(decrec:exp); putln
-    if decrec:exp < 0
+    if decrec:exp < 0 and format & $02
         //
         // Strip off trailing fractional zeros
         //
         while sigdigits > dp and decrec.sig[sigdigits] == '0'
             sigdigits--
+            decrec:exp++
         loop
     fin
+    //sane:zpRestore()
     //puts("sigdigits: "); puti(sigdigits); putln
-    if (decrec:exp + (decrec.sig - sigdigits)) < -numdigits or decrec:exp > 0 or expformat
+    //putc(decrec.sgn ?? '-' :: '+'); puts(@decrec.sig); putc('e'); puti(decrec:exp); putln
+    //sane:zpSave()
+    if sigdigits - decrec:exp > numdigits or decrec:exp > 0 or format & $04
         //
         // Convert to exponential format
         //
@@ -243,7 +251,7 @@ def ext2str(ext, str, numdigits, expformat)
     ^str = i
     return str
 end
-def divstri(strNum, denom, expformat)#0
+def divstri(strNum, denom, format)#0
     byte strResult[20]
     byte xResult[t_extended]
 
@@ -253,7 +261,7 @@ def divstri(strNum, denom, expformat)#0
     sane:zpSave()
     str2ext(strNum, @xResult)
     sane:fpOp2(FFINT|FODIV, @xResult, @denom) // Div int denom into ext Result
-    ext2str(@xResult, @strResult, 6, expformat)
+    ext2str(@xResult, @strResult, format & $05 ?? 1 :: 6, 4, format)
     sane:zpRestore()
     puts(strNum); putc('/'); puti(denom); putc('='); puts(@strResult); putln
 end
@@ -316,13 +324,14 @@ sane:zpRestore()
 //
 // String conversion tests
 //
-divstri("-3", 0, 0)
-divstri("3", 0, 0)
-divstri("-100.5", 4, 0)
-divstri("00.5", 2, 0)
-divstri(".5", 10, 0)
-divstri("800000", 2, 0)
-divstri("800000", 2, 1)
-divstri("1e+2", 2, 0)
-divstri("-1e-2", 2, 0)
+divstri("-3", 0, 2)
+divstri("3", 0, 2)
+divstri("-100.5", 4, 2)
+divstri("00.5", 2, 2)
+divstri(".5", 10, 3)
+divstri("800000", 2, 2)
+divstri("800000", 2, 4)
+divstri("1e+2", 2, 2)
+divstri("-1e-2", 2, 2)
+divstri("0", 1, 2)
 done