diff --git a/system/system.h65 b/system/system.h65
index 058d860..1b0533c 100644
--- a/system/system.h65
+++ b/system/system.h65
@@ -8,43 +8,57 @@
 .ifndef INCLUDE_SYSTEM
 INCLUDE_SYSTEM = 1
 ; reserved RAM addresses
-; 00-0f - free
-; 10-1f - arguments / return values
+; 00-0f - free use  (Z0-Z15)
+; 10-1f - arguments / return values (ARG0-ARG15)
 ; 20-ff - free
 ; 0100 - 01FF Stack
 ; 0200,0201 keybuffer write/read pointer
 ; 0202-02ff keybuffer
 ; 0300 lcd character counter
-; 0400, 0401, 0402 dht status, dht bit, dht_bit_rot
-; 0403 value offset
-; 0405-04a0 rh high/low, temp high/low, checksum
+
 
 .include "io_W65C22.h65"
 .include "utility.h65"
+.importzp Z0,Z1,Z2,Z3,Z4,Z5,Z6,Z7,Z8,Z9,Z10,Z11,Z12,Z13,Z14,Z15
+.importzp ARG0,ARG1,ARG2,ARG3,ARG4,ARG5,ARG6,ARG7,ARG8,ARG9,ARG10,ARG11,ARG12,ARG13,ARG14,ARG15
 
-; ARGUMENTS
-; a,x,y can also be used 
-ARG0    = $10
-ARG1    = $11
-ARG2    = $12
-ARG3    = $13
-ARG4    = $14
-ARG5    = $15
-ARG6    = $16
-ARG7    = $17
-ARG8    = $18
-ARG9    = $19
-ARG10   = $1a
-ARG11   = $1b
-ARG12   = $1c
-ARG13   = $1d
-ARG14   = $1e
-ARG15   = $1f
+; Z0    = $0
+; Z1    = $1
+; Z2    = $2
+; Z3    = $3
+; Z4    = $4
+; Z5    = $5
+; Z6    = $6
+; Z7    = $7
+; Z8    = $8
+; Z9    = $9
+; Z10   = $a
+; Z11   = $b
+; Z12   = $c
+; Z13   = $d
+; Z14   = $e
+; Z15   = $f
+; ; ARGUMENTS
+; ; a,x,y can also be used 
+; ARG0    = $10
+; ARG1    = $11
+; ARG2    = $12
+; ARG3    = $13
+; ARG4    = $14
+; ARG5    = $15
+; ARG6    = $16
+; ARG7    = $17
+; ARG8    = $18
+; ARG9    = $19
+; ARG10   = $1a
+; ARG11   = $1b
+; ARG12   = $1c
+; ARG13   = $1d
+; ARG14   = $1e
+; ARG15   = $1f
 
 
 ; RETURN VALUE 
-; in a
-
 .segment "VIA1"
 ; IO1:    .res 16
 IO1     = $6000
diff --git a/system/system.s65 b/system/system.s65
index 4d8db89..222515f 100644
--- a/system/system.s65
+++ b/system/system.s65
@@ -1,3 +1,42 @@
+; .include "system.h65"
+.exportzp Z0,Z1,Z2,Z3,Z4,Z5,Z6,Z7,Z8,Z9,Z10,Z11,Z12,Z13,Z14,Z15
+.exportzp ARG0,ARG1,ARG2,ARG3,ARG4,ARG5,ARG6,ARG7,ARG8,ARG9,ARG10,ARG11,ARG12,ARG13,ARG14,ARG15
+
 .zeropage
-.org $10
-.res 16
+.org $0
+.assert * = $0, error, "Code not at 0"
+Z0:   .res 1
+Z1:   .res 1
+Z2:   .res 1
+Z3:   .res 1
+Z4:   .res 1
+Z5:   .res 1
+Z6:   .res 1
+Z7:   .res 1
+Z8:   .res 1
+Z9:   .res 1
+Z10:  .res 1
+Z11:  .res 1
+Z12:  .res 1
+Z13:  .res 1
+Z14:  .res 1
+Z15:  .res 1
+; ARGUMENTS
+; a,x,y can also be used 
+.assert * = $10, error, "Code not at 10"
+ARG0:     .res 1
+ARG1:     .res 1
+ARG2:     .res 1
+ARG3:     .res 1
+ARG4:     .res 1
+ARG5:     .res 1
+ARG6:     .res 1
+ARG7:     .res 1
+ARG8:     .res 1
+ARG9:     .res 1
+ARG10:    .res 1
+ARG11:    .res 1
+ARG12:    .res 1
+ARG13:    .res 1
+ARG14:    .res 1
+ARG15:    .res 1