a5: Addition oder Substraktion

src/c/a5/addsub.asm

@@ -13,10 +13,25 @@ addsub:
     mov [ebp-4], word 1
 
     mov eax, 0
-    add ax, word [foo]
+
+    mov operation, word [ebp+16]
+
     add ax, word [ebp+8]
-    add ax, word [ebp-4]
+
+    cmp operation, 0x2b
+    jne substract
+
+    add ax, word [ebp-12]
+    jmp return
+
+substract: sub ax, word [ebp-12]
+
+return:
 
     mov esp, ebp
     pop ebp
     ret
+
+section .data
+
+operation dw 2