Use backtick code blocks for syntax highlighting

06-01.md

@@ -120,10 +120,14 @@ For example, suppose you have an array base address in BX and an index
 into the array in SI. You could add the two registers together to
 address memory, like this:
 
-    add  bx,si
-    mov  al,[bx]
+```nasm
+add  bx,si
+mov  al,[bx]
+```
 
 Or you could let the processor do the arithmetic for you in a single
 instruction:
 
-    mov  al,[bx+si]
+```nasm
+mov  al,[bx+si]
+```