Editing Binary-coded decimal (section)

==Representational variations==
Various BCD implementations exist that employ other representations for numbers. [[Programmable calculator]]s manufactured by [[Texas Instruments]], [[Hewlett-Packard]], and others typically employ a [[floating-point]] BCD format, typically with two or three digits for the (decimal) exponent. The extra bits of the sign digit may be used to indicate special numeric values, such as [[infinity]], [[arithmetic underflow|underflow]]/[[arithmetic overflow|overflow]], and [[Defined and undefined|error]] (a blinking display).

===Signed variations===
Signed decimal values may be represented in several ways. The [[COBOL]] programming language, for example, supports five zoned decimal formats, with each one encoding the numeric sign in a different way:
{| class="wikitable" style="width:95%"
|-
! style="background:#D0E0FF; width:25%"| Type
! style="background:#D0E0FF; width:55%"| Description
! style="background:#D0E0FF; width:20%"| Example
|-
| [[Signed number representations|Unsigned]]
| No sign [[nibble]]
| <code>F1 F2 <u>F</u>3</code>
|-
| Signed trailing ''(canonical format)''
| Sign nibble in the last (least significant) byte
| <code>F1 F2 <u>C</u>3</code>
|-
| Signed leading ''(overpunch)''
| Sign nibble in the first (most significant) byte
| <code><u>C</u>1 F2 F3</code>
|-
| Signed trailing separate
| Separate sign character byte (<code>'+'</code> or <code>'−'</code>) following the digit bytes
| <code>F1 F2 F3 <u>2B</u></code>
|-
| Signed leading separate
| Separate sign character byte (<code>'+'</code> or <code>'−'</code>) preceding the digit bytes
| <code><u>2B</u> F1 F2 F3</code>
|}

==={{anchor|TBCD}}Telephony binary-coded decimal (TBCD)===
[[3GPP]] developed '''TBCD''',<ref name="3GPP_2013_TS29002"/> an expansion to BCD where the remaining (unused) bit combinations are used to add specific [[telephony]] symbols,<ref name="ETSI_SPS"/><ref name="OpenSS_XMAP"/> similar to those in [[DTMF|telephone keypad]] design.
{| class="wikitable" style="width:30%; text-align:center"
|-
! style="background:#E0E0E0; width:50%" |Decimal<br />digit
! style="background:#E0E0E0; width:50%" |TBCD<br />8 4 2 1
|-
! style="background:#F0F0F0" |*
| 1 0 1 0
|-
! style="background:#F0F0F0" |#
| 1 0 1 1
|-
! style="background:#F0F0F0" |a
| 1 1 0 0
|-
! style="background:#F0F0F0" |b
| 1 1 0 1
|-
! style="background:#F0F0F0" |c
| 1 1 1 0
|-
! style="background:#F0F0F0" |Used as filler when there is an odd number of digits
| 1 1 1 1
|}

The mentioned 3GPP document defines '''TBCD-STRING''' with swapped nibbles in each byte. Bits, octets and digits indexed from 1, bits from the right, digits and octets from the left.
<blockquote>
bits 8765 of octet ''n'' encoding digit 2''n''

bits 4321 of octet ''n'' encoding digit 2(''n'' – 1) + 1
</blockquote>

Meaning number <code>1234</code>, would become <code>21 43</code> in TBCD.

This format is used in modern [[mobile telephony]] to send dialed numbers, as well as [[Mobile country code|operator ID]] (the MCC/MNC tuple), [[International Mobile Equipment Identity|IMEI]], [[International mobile subscriber identity|IMSI]] (SUPI), et.c.<ref>{{cite web|url=https://www.etsi.org/deliver/etsi_ts/124500_124599/124501/16.10.00_60/ts_124501v161000p.pdf|title=Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3. (3GPP TS 24.501 version 16.10.0 Release 16) TS 24.501 release 16.10.0|publisher=[[ETSI]] and [[3GPP]]|access-date=February 26, 2022|archive-date=February 17, 2022|archive-url=https://web.archive.org/web/20220217231615/https://www.etsi.org/deliver/etsi_ts/124500_124599/124501/16.10.00_60/ts_124501v161000p.pdf|url-status=live}} (TS 24.501)</ref><ref>{{cite web|url=https://www.etsi.org/deliver/etsi_ts/123000_123099/123003/16.08.00_60/ts_123003v160800p.pdf|title=Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; 5G; Numbering, addressing and identification (3GPP TS 23.003 version 16.8.0 Release 16)|publisher=[[ETSI]] and [[3GPP]]|access-date=February 26, 2022|archive-date=February 26, 2022|archive-url=https://web.archive.org/web/20220226144220/https://www.etsi.org/deliver/etsi_ts/123000_123099/123003/16.08.00_60/ts_123003v160800p.pdf|url-status=live}} (TS 23.003)</ref>