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44-04.md

@@ -74,10 +74,12 @@ way back in Chapter 24.) So, for example, if write mode 3 is enabled and
 the Set/Reset register is set to 1 (blue), then the following sequence
 of operations:
 
-    mov   dx,0a000h
-    mov   es,dx
-    mov   al,es:[0]
-    mov   byte ptr es:[0],0f0h
+```nasm
+mov   dx,0a000h
+mov   es,dx
+mov   al,es:[0]
+mov   byte ptr es:[0],0f0h
+```
 
 will change the first 4 pixels on the screen (the left nibble of the
 byte at offset 0 in display memory) to blue, and will leave the next 4
@@ -88,10 +90,12 @@ display memory is not particularly efficient on some processors. In
 Listing 44.2, I instead use **XCHG**, which reads and then writes a
 memory location in a single operation, as in:
 
-    mov    dx,0a000h
-    mov    es,dx
-    mov    al,0f0h
-    xchg   es:[0],al
+```nasm
+mov    dx,0a000h
+mov    es,dx
+mov    al,0f0h
+xchg   es:[0],al
+```
 
 Again, the actual value that's read is irrelevant. In general, the
 **XCHG** approach is more compact than two **MOV**s, and is faster on
@@ -103,9 +107,11 @@ information in display memory at that byte needs to be preserved; a
 simple write of 0FFH (to draw all bits) will set all 8 pixels to the
 set/reset color:
 
-    mov   dx,0a000h
-    mov   es,dx
-    mov   byte ptr es:[di],0ffh
+```nasm
+mov   dx,0a000h
+mov   es,dx
+mov   byte ptr es:[di],0ffh
+```
 
 > ![](images/i.jpg)
 > If you're familiar with VGA programming, you're no doubt aware that