Update bitwise logic operators

Author: boriel

docs/architectures/bitwiselogic.md

@@ -0,0 +1,94 @@
+#Bitwise Operators
+
+ZX Basic allows Bit Manipulation (bitwise), on every integer type (from 8 to 32 bits).
+
+| **BITWISE OPERATORS** |
+|: ---------------------------- :|
+| bAND |
+| bOR  |
+| bNOT |
+| bXOR |
+
+Except bNOT, all the others require two integral (Byte, Ubyte, Integer, UInteger, Long, ULong) operands.
+The operation will be applied bit by bit.
+
+---
+##bAND
+
+Performs the _Bitwise Conjunction_ and returns 1 for every bit if and only if both bits are 1.
+
+| a  | b  | result |
+|:----:|:----:|:------:|
+|  0  | 0  |  0 |
+|  0  | 1  | 0 |
+|  1  | 0  |  0 |
+|  1  | 1  |  1 |
+
+###Example
+
+Binary "mask" that will get only the 4 rightmost bits 0 1 2 3 of a number:
+
+`PRINT BIN 01110111 bAND BIN 00001111` will print 3, which is 0111`
+
+---
+
+## bOR
+
+Performs the _Bitwise Disjunction_ and returns 1 if any of the arguments is 1.
+
+| a  | b  | result |
+|:----:|:----:|:------:|
+|  0  | 0 |  0 |
+|  0  | 1  | 1 |
+|  1  | 0 |  1 |
+|  1  | 1  |  1 |
+
+###Example
+
+Ensure an ASCII letter is always in lowercase:
+
+`PRINT CHR$(CODE "A" OR BIN 10000)` will print `a` because lowercase letters have bit 5 set.
+
+---
+
+## bNOT
+
+Performs the _Bitwise Negation_ and returns _1_ if the arguments is _0_ and vice versa. 
+Basically it flips all the bits in an integer number.
+
+| a  |result |
+|:----:|:------:|
+|  0  | 1  |
+|  1  | 0  |
+
+
+###Example
+
+Invert the first cell (upper-leftmost) in the screen:
+
+```
+PRINT AT 0, 0; "A";
+FOR i = 0 TO 3
+    POKE 16384 + 256 * i, bNOT PEEK(16384 + 256 * i)
+NEXT
+```
+---
+
+#bXOR
+
+Performs a logical XOR and returns 1 if one and only one of the arguments is 1, 0 if both bits are the same.
+In essence, returns 1 ONLY if one of the arguments is 1. 
+
+| a  | b  | result |
+|:----:|:----:|:------:|
+|  0  | 0 |  0 |
+|  0  | 1  | 1 |
+|  1  | 0 |  1 |
+|  1  | 1  |  0 |
+---
+
+###Example
+
+Flips an ASCII letter from lower to uppercase and vice versa
+
+`PRINT CHR$(CODE "A" bXOR BIN 10000)`