added stack

ass1/stack.asm

@@ -0,0 +1,56 @@
+.code
+
+stack   START   0
+
+	LDA   #9
+   	STA   @stackptr
+   	JSUB  stackpush     . PUSHA
+
+  	JSUB  stackpop      . POPA
+	LDA   @stackptr
+
+halt    J       halt
+
+
+stackinit
+        STA     stacktmp       
+
+        LDA     #STACK          
+        STA     stackptr       
+
+        LDA     stacktmp        
+        RSUB
+
+
+stackpush
+        STA     stacktmp        
+
+        LDA     stackptr
+        ADD     #3              
+        STA     stackptr
+
+        LDA     stacktmp        
+        RSUB
+
+
+stackpop
+        STA     stacktmp        
+
+        LDA     stackptr
+        SUB     #3              
+        STA     stackptr
+
+        LDA     stacktmp        
+        RSUB
+
+
+.data
+
+stackptr    WORD    0
+
+stacktmp    WORD    0
+
+STACKSIZE   EQU     50          
+STACK       RESW    STACKSIZE
+
+        END     stack