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98 lines
2.8 KiB
Markdown
98 lines
2.8 KiB
Markdown
The [RESTORE](RESTORE) statement is used to reset the DATA pointer to the beginning of the data.
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## Syntax
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> [RESTORE](RESTORE) [lineNumber|lineLabel]
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## Description
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* The line label or number enables a labeled data field to be [READ](READ) more than once as required.
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* Datafield label names are not required when working with ONE or a progression of data fields in the main body of code.
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* Label multiple data fields to restore them to use them again when necessary.
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* If RESTORE is used with unlabeled data fields or no datafield is designated then the first data field is read.
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* Use RESTORE to avoid an [ERROR Codes](ERROR-Codes) when reading a data field!
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* See the [DATA](DATA) statement for [STRING](STRING) data value specifications.
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* **Do not place [DATA](DATA) fields after [SUB](SUB) or [FUNCTION](FUNCTION) procedures! QB64 will FAIL to [RESTORE](RESTORE) properly!**
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> QBasic allowed programmers to add DATA fields anywhere because the IDE separated the main code from other procedures.
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## Example(s)
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Restoring a labeled DATA field to avoid going past the end of DATA.
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```vb
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DO
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INPUT "Enter a month number(1 to 12): ", monthnum%
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RESTORE Months
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FOR i = 1 TO monthnum%
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READ month$, days% 'variables must match data field types
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NEXT
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PRINT "The month "; month$; " has"; days%; "days."
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LOOP UNTIL monthnum% < 1 OR monthnum% > 12
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Months:
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DATA January, 31, February, 28, March, 31, April, 30, May, 31, June, 30
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DATA July, 31, August, 31, September, 30, October, 31, November, 30, December, 31
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```
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```text
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Enter a month number(1 to 12): 6
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The month June has 30 days.
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```
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> *Note:* String DATA values do not require quotes unless they have commas, end spaces or QBasic keywords in them.
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Using RESTORE to know the number of elements in the DATA in order to dimension and store the items in a array.
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```vb
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DO
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READ dummy$ 'we won't actually use this string for anything else than to know when there is no more DATA.
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count = count + 1
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LOOP UNTIL dummy$ = "stop" 'when dummy$ = "stop" then we know that it is the last entry so it only does the above loop until then.
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count = count - 1 'since the last string is "stop" and we don't want to store it in the array.
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PRINT "The number of relevant entries are:"; count
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DIM entry$(count) 'Now we know how many elements we need to make space for (DIM)
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RESTORE 'We restore it so that it begins reading from the first DATA again.
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FOR c = 1 TO count
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READ entry$(c) 'read the DATA and store it into the array.
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NEXT
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'we can now print the contents of the array:
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FOR c = 1 TO count
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PRINT entry$(c)
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NEXT
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END
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DATA "entry1", "entry2", "entry3", "stop"
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```
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```text
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The number of relevant entries are: 3
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entry1
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entry2
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entry3
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```
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*Note:* Now we can add any number of entries without further compensation to the code.
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## See Also
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* [DATA](DATA), [READ](READ)
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* [line numbers](line-numbers) / line labels
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