Variables - Formats - Encoding - Binary

2015-01-26T23:15:08Z

DoyleChris: /* BCD32 - 4 BYTES */

{{:Ambox-Content-WIP}}
{{Infobox-Applicable-FSVersion
| FSXI = false
| FSXA = true
| FSX = true
| FS2004 = true
| FS2002 = true
| FS2000 = false
| FS98 = false
}}
Placeholder for Variables - Formats - Encoding - Binary related info.

For passing info to gauges, or into missions via SimConnect applets.

== Binary-Encoding ==
In a fixed-width binary code, each letter, digit, or other character, is represented by a sequence of bits of the same length,
 
usually indicated in code tables by the octal, decimal or hexadecimal notation for the value of that sequence of bits interpreted as a binary number.
 
i.e. A method of coding data, as sequences of characters.

Binary-coded decimal, (BCD),is a method of storing individual decimal based characters.
 
Binary-coded octal, (BCO), is the octal equivalent.

== Example Legibility ==
Requires checking -

For legibility purposes only, the examples below include spaces, dots, hyphens, etc. as seperators.
 
Your code should not include those characters.

== Binary-Coded Decimal (BCD) ==
Used in - ???

A method of storing individual digits for 'easy' manipulation.
 
The implementation used in FS is actually "Packed BCD",
where one BCD digit is stored in each half byte, (aka nibble).

=== 1 BYTE ===
Just for explaining the principle.
 
These are the BITs in a 8 bit number with their order value for a BCD encoded number:
<PRE>
8 4 2 1 . 8 4 2 1
</PRE>

Example -
 
0001-0111 is 1-7 which is 1x10 + 7x1 = 17
 
One BCD digit is stored in each half byte, (aka nibble).

=== Storage Types ===
BCD 16 or 32 defines the storage type -

typedef VAR16 BCD16, *PBCD16, **PPBCD16; // 4-digit BCD number (0000-9999)
 
typedef VAR32 BCD32, *PBCD32, **PPBCD32; // 8-digit BCD number (00000000-99999999)

=== BCD16 - 2 BYTES ===
Used in - ???

These are the BITs in a 16 bit number with their order value for a BCD encoded number:
<PRE>
8 4 2 1 . 8 4 2 1 . 8 4 2 1 . 8 4 2 1
</PRE>

This is 2 bytes and can store a 4 digit BDC16 encoded number,
 
with one BCD digit stored in each half byte, (aka nibble).

Example -
 
0011-0110 0010-0101 is 3-6 2-5 which is 3x100 + 6x10 + 2x1 + 5x0.1 = 362.5

Useage -
 
FS example required

==== Note - ====
For COM and NAV frequencies there's a legacy related matter -
 
Since the highest order digit in the instrument (gauge) is always 1 (one),
 
it is not recorded in the BCD representation to save space. (now only 4 digits have to be stored)

e.g.
 
For a frequency of 136.25
 
1 is assumed
 
so the recorded BCD is 3625

=== BCD32 - 4 BYTES ===
Used in - ADF Radios

These are the BITs in a 32 bit number with their order value for a BCD encoded number:
<PRE>
8 4 2 1 . 8 4 2 1 . 8 4 2 1 . 8 4 2 1 . 8 4 2 1 . 8 4 2 1 . 8 4 2 1 . 8 4 2 1
</PRE>

BCD32 is 4 bytes for an 8 digit BCD encoded number,
 
again with one BCD digit stored in each half byte, (aka nibble).

Example -
 
THIS EXAMPLE NEEDS CHECKING/CORRECTING
 
0001-0011 1000-0100 0101-0000 0000-0000 is 1-3 8-4 5-0 0-0 which is 1x1000 + 3x100 + 8x10 + 4x1 + 5x0.1 = 1384.5

Useage - ADF Radios
 
FS example required

== Binary-Coded Octal (BCO) ==
Equivalent for Octal required.

== Related ==
Hex-Decimal-Binary online converter at - http://flor.nl/dec2hex.html

[[category:Aircraft Design]]
[[category:Panel and Gauge Design]]

FSDeveloper Wiki - User contributions [en-gb]

Variables - Formats - Encoding - Binary