Update 671-language-nand.markdown

Author: Joe7M

_build/reference/671-language-nand.markdown

@@ -1,15 +1,52 @@
 # NAND
 
-> a NAND b
+> y = a NAND b
 
 Bitwise exclusive NOT AND.
 
+Truth table:
 
-~~~
+| a | b | a NAND b |
+|:-:|:-:|:--------:|
+|0  | 0 | 1        |
+|0  | 1 | 1        |
+|1  | 0 | 1        |
+|1  | 1 | 0        |
 
+
+### Example 1
+
+The NOT-operation as part of NAND performs a bitwise inversion on all bits of a number. This leads to the following (maybe unexpected) result: 
+
+```
+print 1 NAND 1   ' Output: 11111111111111111111111111111110
+```
+
+### Example 2: Operate NAND only on last n bits
+
+If you want to operate NAND only on the last `n` bits of the numbers, you can use the following code:
+
+```
+n = 4
+a = 0b1101
+b = 0b1001
+
+print bin((a NAND b) BAND ((1 lshift n ) - 1)) 
+
+' Output 110
+```
+
+### Example 3: Two's complement
+
+> Two's complement is a mathematical operation to reversibly convert
+> a positive binary number into a negative binary number with equivalent negative value. ([Wikipedia](https://en.wikipedia.org/wiki/Two%27s_complement))
+
+```
 ' Two's complement is the standard way of representing negative integers in binary. 
 ' The sign is changed by inverting all of the bits and adding one.
-Def invsgn(n) = ((n Nand n) + 1) - Frac(n) ' invert the sign of n
+
+Def invsgn(n) = ((n Nand n) + 1) - Frac(n)              ' invert the sign of n
+
 While True Do
   Input "Enter a number (Enter empty to stop) : ", n
   If Isstring(n) Then
@@ -19,7 +56,7 @@ While True Do
   Print "This is the number with inverted sign: "; invsgn(n)
   Print
 Wend
+```
 
-~~~