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| Contributions |
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| 2021-05-05 17:24:29  JimPeterson  wrote:
| requestClarification - Web site problem?
| see: https://forth-standard.org/standard/right-bracket#contribution-197
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This entry on the web site seems a bit messed up, being different from all other entries.  It looks like something went wrong.


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| Replies |
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| 2021-05-02 12:32:34  ruv  replies:
| requestClarification - Return value of XC-WIDTH for control characters
| see: https://forth-standard.org/standard/xchar/XC-WIDTH#reply-678
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> what the width should be for control characters ( 1 to $1F and $80 to $9F )

Whatever it should be, it should be specified — zero, one, or system dependent.

The space that a control character takes depends on the environment and context. E.g. Tab (0x9) can take from 1 to 8  [em](https://en.wikipedia.org/wiki/Em_(typography)) (depending on the position on the display, and the display properties). Bell (0x7) usually takes 0 em.

Obviously, a Forth system cannot return the actual width for control characters in all cases.

If a program knows the environment and wants to calculate the actual width of a **string**, it should implement its own version of [`X-WIDTH`](/standard/xchar/X-WIDTH). And then it doesn't matter what `XC-WIDTH` returns for control characters. But what `XC-WIDTH` returns should be good enough as a fallback.

Perhaps a good enough approach is to suppose that the control characters don't have any "control" function and they are mapped to some real characters and displayed as usual characters. And then `XC-WIDTH` should return `1` for them.

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A side note. In XML the most control characters are illegal due to unclear semantics in the context of XML (see useful [comments at StackOverflow](https://stackoverflow.com/questions/404107/why-are-control-characters-illegal-in-xml-1-0)).



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| 2021-05-02 15:10:25  StephenPelc  replies:
| requestClarification - How many cells can be compared ? Must have any limit ?
| see: https://forth-standard.org/standard/string/COMPARE#reply-679
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Note that where the standard mentions characters, it nearly always means "primitive characters" or pchars for short. With the AU=1 decision, this means bytes in all practical cases. UTF-16 systems need to use XCHAR operations. KEY and EMIT are still there to handle 8 bit operations such as Telnet. Note also that on most implementations, TCP/IP and USB operations can have packet breaks in the middle of UTF-16 characters.