<p>In the custom uint256 encoding used in Bitcoin, bit 0x00800000 denotes the sign, so 0x1CFFFFFF actually denotes the value <em>-2<sup>200</sup>(2<sup>23</sup> - 1)</em>. Obviously the target value cannot go negative, so this aspect of the encoding is not useful in this context, but for whatever reason, that's what Bitcoin's creator chose.</p>

CC BY-SA 4.0
2022-04-30T20:01:11.397Z
Thank you that was helpful. I am not so deep in coding. That means when I am looking at the last 6 digits 000000 to 7FFFFF are positive and 800000 to FFFFFF are negative?
steff123
CC BY-SA 4.0
2022-04-30T21:44:38.123Z
@steff123 That's right.
Pieter Wuille
CC BY-SA 4.0
2022-04-30T17:48:37.087Z
2022-05-08T21:18:53.260Z
2022-05-08T21:18:53.260Z
Pieter Wuille
<p>Is there a specific reason why 1D00FFFF is the target bit for the genesis block and not 1CFFFFFF? Both bits are forcing 8 zeros in the front of the hash (hexadecimal).</p>
<p>Regards steff</p>

<genesis-block><difficulty-retargetting>
Why 1D00FFFF and not 1CFFFFFF as target in genesis block
steff123
# Why 1D00FFFF and not 1CFFFFFF as target in genesis block

(Asked by: username_0 on 2022-04-30)

Is there a specific reason why 1D00FFFF is the target bit for the genesis block and not 1CFFFFFF? Both bits are forcing 8 zeros in the front of the hash (hexadecimal).

Regards steff

**Tags:** genesis-block, difficulty-retargetting


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## 1 answers

### Answer by username_1 on 2022-04-30. Score: 2 | Accepted answer

In the custom uint256 encoding used in Bitcoin, bit 0x00800000 denotes the sign, so 0x1CFFFFFF actually denotes the value *-2200(223 - 1)*. Obviously the target value cannot go negative, so this aspect of the encoding is not useful in this context, but for whatever reason, that's what Bitcoin's creator chose.

> **Comments:**
> **username_0**: Thank you that was helpful. I am not so deep in coding. That means when I am looking at the last 6 digits 000000 to 7FFFFF are positive and 800000 to FFFFFF are negative?  
> **username_1**: @username_0 That's right.  

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