Bitwise Operations - Revision history

RanXerox: /* The NOT Operator */

2015-11-05T19:53:28Z

‎The NOT Operator

RanXerox: /* The XOR Operator (exclusive OR) */

2015-11-05T19:49:48Z

‎The XOR Operator (exclusive OR)

RanXerox: /* The AND Operator: & */

2015-11-05T19:42:53Z

‎The AND Operator: &

RanXerox: /* The OR Operator (inclusive OR) */

2015-11-05T19:41:55Z

‎The OR Operator (inclusive OR)

RanXerox: /* The AND Operator */

2015-11-05T19:17:13Z

‎The AND Operator

RanXerox: /* Flags */

2015-11-05T18:52:10Z

‎Flags

RanXerox: /* Flags */

2015-11-05T18:48:44Z

‎Flags

RanXerox: /* The OR Operator (inclusive OR) */

2015-11-05T18:41:08Z

‎The OR Operator (inclusive OR)

RanXerox at 21:46, 28 November 2013

2013-11-28T21:46:47Z

RanXerox: /* Converting from decimal to binary and from binary to decimal */

2013-03-28T22:49:44Z

‎Converting from decimal to binary and from binary to decimal

@@ Line 141: / Line 141: @@
     = 1000 (decimal 8)
-==The NOT Operator==
+==The NOT Operator (bitwise not): !==
 ==Left and right shift==

@@ Line 128: / Line 128: @@
   IF (<ATTR>&attr_identified)
-==The XOR Operator (exclusive OR)==
+==The XOR Operator (exclusive OR): ^==
 ==The NOT Operator==
 ==Left and right shift==

@@ Line 111: / Line 111: @@
   ATTR|=attr_move_always
-==The AND Operator: &==
+==The AND Operator (logical and): &==
 A ''bitwise AND'' takes two equal-length binary representations and performs the ''logical AND operation'' on each pair of the corresponding bits, by multiplying them. If both bits in the compared position are 1, the bit in the resulting binary representation is 1 (1 × 1 = 1); otherwise, the result is 0 (1 × 0 = 0 and 0 × 0 = 0). For example:

@@ Line 85: / Line 85: @@
 Now you can probably see the pattern... the numbers 1,2,4,8,16,32,64,128,... are all multiples of 2 and they are special because they all have a single 1 in them when converted to binary.  To enable or disable an individual flag on an object is accomplished using the bitwise operators AND, OR, XOR, and NOT.
-==The OR Operator (inclusive OR)==
+==The OR Operator (inclusive OR): |==
 A ''bitwise OR'' takes two bit patterns of equal length and performs the logical ''inclusive OR'' operation on each pair of corresponding bits. When you perform this operation, the result in each position is 0 if both bits are 0, and the result is 1 if either (or both) the bits were 1. For example:
@@ Line 93: / Line 93: @@
    = 0111 (decimal 7)
-In Sphere, this technique is commonly used to set a ''flag'' in a register, where each bit represents an individual Boolean state. Thus, 0010 (decimal 2) can be considered a set of four flags, where the first, third, and fourth flags are clear (0) and the second flag is set (1). The fourth flag may be set by performing a bitwise OR between this value and a bit pattern with only the fourth bit set:
+In Sphere, this technique is commonly used to set a ''flag'' in a register, while preserving the existing flags.  So, 0010 (decimal 2) can be considered a set of four flags, where the first, third, and fourth flags are clear (0) and the second flag is set (1). The fourth flag may be set by performing a bitwise OR between this value and a bit pattern with only the fourth bit set:
 (decimal 2)
   OR 1000 (decimal 8)
    = 1010 (decimal 10)
 ==The AND Operator: &==

@@ Line 99: / Line 99: @@
    = 1010 (decimal 10)
-==The AND Operator==
+==The AND Operator: &==
 ==The XOR Operator (exclusive OR)==
 ==The NOT Operator==

@@ Line 73: / Line 73: @@
 |-
 |Flag Name:     ||  attr_invis||  attr_owned||  attr_magic||attr_move_never||attr_move_always||  attr_newbie||  attr_decay||attr_identified
 |-
 |Binary Number: ||    10000000||    01000000||    00100000||       00010000||        00001000||     00000100||    00000010||       00000001

@@ Line 68: / Line 68: @@
   attr_secure     01000000
-Notice a pattern?  Let's tip it on it's side and chart the first 8 flags:
+This technique is a very efficient way to store a number of Boolean values using as little memory as possible.  Let's tip that list on it's side and chart the first 8 flags:
 {|border=1 cellpadding=5
@@ Line 80: / Line 80: @@
 |Decimal Number:||         128||          64||          32||             16||               8||            4||           2||              1
 |}
 ==The OR Operator (inclusive OR)==

@@ Line 1: / Line 1: @@
-Bitwise operations are used to perform an action on the bits (the 1's and 0's) of a number.  Understanding what bitwise operators do requires you to understand how to convert from decimal to binary and from binary to decimal.
+Bitwise operations are used to perform an action on the bits (the 1's and 0's) of a number.
 In this article a "binary" formatted number (which represents the "bits" of a number) will be written with a <sup>2</sup>... and a decimal number with a <sup>10</sup>
 ==Converting from decimal to binary and from binary to decimal==
@@ Line 62: / Line 150: @@
 # Therefore, the negative binary number 1111111111010011<sup>2</sup> is equal to the decimal number -45<sup>10</sup>
-==The OR Operator (inclusive OR)==
+-->

@@ Line 5: / Line 5: @@
 ==Converting from decimal to binary and from binary to decimal==
-For example 11010011<sup>2</sup> is equal to 21110<sup>10</sup>, and 14310<sup>10</sup> is equal to 10001111<sup>2...
+For example 11010011<sup>2</sup> is equal to 21110<sup>10</sup>, and 14310<sup>10</sup> is equal to 10001111<sup>2</sup>...
 ;From decimal to binary