# Numbering rule of scifunc\_block input / output port

**URL:** <https://scilab.discourse.group/t/numbering-rule-of-scifunc-block-input-output-port/599>\
**Category:** Xcos\
**Created:** [July 30, 2024, 1:52am UTC](https://scilab.discourse.group/t/numbering-rule-of-scifunc-block-input-output-port/599 "2024-07-30T01:52:41Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Alex](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@Alex](https://scilab.discourse.group/u/Alex)\
**Post date:** [July 30, 2024, 1:52am UTC](https://scilab.discourse.group/t/numbering-rule-of-scifunc-block-input-output-port/599/1 "2024-07-30T01:52:41Z")

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In Xcos, when I edit the scifunc\_block as below, which port is u1, u2, u3 and y1, y2, y3?  
Is there any numbering rule of input / output port number?  
For example, from upside to downside u1, u2, u3,… , y1, y2, y3,…  
Please teach me.

 ![scifunc_block](https://global.discourse-cdn.com/free1/uploads/utc/original/1X/bd07acee1037d0a21999a70f9ba7da62c59b78e5.jpeg)

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**Author:** ![davidcl](https://yyz2.discourse-cdn.com/free1/user_avatar/scilab.discourse.group/davidcl/32/1029_2.png) [@davidcl](https://scilab.discourse.group/u/davidcl)\
**Post date:** [August 13, 2024, 8:57am UTC](https://scilab.discourse.group/t/numbering-rule-of-scifunc-block-input-output-port/599/2 "2024-08-13T08:57:11Z")

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Hi,

You are correct :

- `u1` is for the first input, `u2` for the second input, etc…
- `y1` is for the first output, `y2` for the second output, etc…

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<div class="post-metadata">

**Author:** ![Alex](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@Alex](https://scilab.discourse.group/u/Alex)\
**Post date:** [August 18, 2024, 10:55pm UTC](https://scilab.discourse.group/t/numbering-rule-of-scifunc-block-input-output-port/599/3 "2024-08-18T22:55:33Z")

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Dear davidcl

Thank you very much for your reply.  
I understood my recognition is correct.

Best regards.