diff --git a/crt0.o b/crt0.o
index f6703be..e0a0fd9 100644
Binary files a/crt0.o and b/crt0.o differ
diff --git a/crt0.s b/crt0.s
index 492179c..4dc7225 100644
--- a/crt0.s
+++ b/crt0.s
@@ -1,38 +1,53 @@
-.export _init, _exit
-.exportzp sp
-.import _main
+; ---------------------------------------------------------------------------
+; crt0.s
+; ---------------------------------------------------------------------------
+;
+; Startup code for cc65 (Single Board Computer version)
 
-.export __STARTUP__: absolute = 1
-.import __RAM_START__, __RAM_SIZE__
+.export   _init, _exit
+.import   _main
 
-.import copydata, zerobss, initlib, donelib
+.export   __STARTUP__ : absolute = 1        ; Mark as startup
+.import   __RAM_START__, __RAM_SIZE__       ; Linker generated
 
-; .include "zeropage.inc"
+.import    copydata, zerobss, initlib, donelib
 
-; reserve byte or sp
-.segment "ZEROPAGE"
-sp: .res 1
+.include  "zeropage.inc"
 
+; ---------------------------------------------------------------------------
+; Place the startup code in a special segment
 
+.segment  "STARTUP"
 
-.segment "STARTUP"
+; ---------------------------------------------------------------------------
+; A little light 6502 housekeeping
 
-_init: ldx #$ff
-        txs
-        cld
+_init:    LDX     #$FF                 ; Initialize stack pointer to $01FF
+          TXS
+          CLD                          ; Clear decimal mode
 
-        lda #<(__RAM_START__ + __RAM_SIZE__)
-        STA sp
-        lda #>(__RAM_START__ + __RAM_SIZE__)
-        STA sp+1
+; ---------------------------------------------------------------------------
+; Set cc65 argument stack pointer
 
-        jsr zerobss
-        jsr copydata
-        jsr initlib
+          LDA     #<(__RAM_START__ + __RAM_SIZE__)
+          STA     sp
+          LDA     #>(__RAM_START__ + __RAM_SIZE__)
+          STA     sp+1
 
-        jsr _main
+; ---------------------------------------------------------------------------
+; Initialize memory storage
 
-_exit:
-        jsr donelib
-        brk
+          JSR     zerobss              ; Clear BSS segment
+          JSR     copydata             ; Initialize DATA segment
+          JSR     initlib              ; Run constructors
 
+; ---------------------------------------------------------------------------
+; Call main()
+
+          JSR     _main
+
+; ---------------------------------------------------------------------------
+; Back from main (this is also the _exit entry):  force a software break
+
+_exit:    JSR     donelib              ; Run destructors
+          BRK
\ No newline at end of file
diff --git a/macro.sh b/macro.sh
index 1df0023..b8cc8eb 100755
--- a/macro.sh
+++ b/macro.sh
@@ -1,6 +1,6 @@
-cc65  test.c -o test.s
+cc65 -t none test.c -o test.s
 ca65  test.s -o test.o
 # ca65 startup.s -o startup.o
-ca65 zeropage.s -o zeropage.o
-ca65 crt0.s -o crt0.o
-ld65 crt0.o zeropage.o test.o -o test -C test.cfg
\ No newline at end of file
+# ca65 zeropage.s -o zeropage.o
+# ca65 crt0.s -o crt0.o
+ld65  zeropage.o test.o sbc.lib -o test -C test.cfg
\ No newline at end of file
diff --git a/ref.txt b/ref.txt
index 156bc69..cd1b831 100644
--- a/ref.txt
+++ b/ref.txt
@@ -2,4 +2,6 @@ https://www.qmtpro.com/~nes/misc/nestest.txt
 https://www.pagetable.com/?p=410
 https://pegvin.github.io/6502/index.html
 https://www.westerndesigncenter.com/wdc/documentation/w65c02s.pdf
-vasm6502_std -Fbin -Felf -mid=PC386 test.asm -o out
\ No newline at end of file
+vasm6502_std -Fbin -Felf -mid=PC386 test.asm -o out
+https://cc65.github.io/doc/customizing.html#s1
+/usr/share/cc65
\ No newline at end of file
diff --git a/sbc.lib b/sbc.lib
new file mode 100644
index 0000000..1284bfc
Binary files /dev/null and b/sbc.lib differ
diff --git a/test.cfg b/test.cfg
index a358fec..9e88781 100644
--- a/test.cfg
+++ b/test.cfg
@@ -7,7 +7,7 @@ MEMORY {
 
 SEGMENTS {
     ZEROPAGE: load = ZP,  type = zp;
-    DATA:     load = RAM, type = rw;
+    DATA:     load = RAM, type = rw, run = RAM;
     CODE:     load = ROM, type = ro;
     HEAP:    load = RAM, type = rw optional = yes;
     INIT:   load = ROM, type = ro optional = yes;
@@ -19,6 +19,17 @@ SEGMENTS {
     # ONCE:     load = ROM, type = ro, optional = yes;
 }
 
+FEATURES {
+    CONDES:    segment = STARTUP,
+               type    = constructor,
+               label   = __CONSTRUCTOR_TABLE__,
+               count   = __CONSTRUCTOR_COUNT__;
+    CONDES:    segment = STARTUP,
+               type    = destructor,
+               label   = __DESTRUCTOR_TABLE__,
+               count   = __DESTRUCTOR_COUNT__;
+}
+
 SYMBOLS { 
     __STACKSIZE__: type = weak, value = $0200; 
     # __RAM_START__: type = weak, value = $0200;
diff --git a/test.o b/test.o
index d66b34c..15bdbf1 100644
Binary files a/test.o and b/test.o differ
diff --git a/zeropage.o b/zeropage.o
index 838d475..b1f2501 100644
Binary files a/zeropage.o and b/zeropage.o differ