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88 lines
3.1 KiB
Text
88 lines
3.1 KiB
Text
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The '''RESTORE''' statement is used to reset the DATA pointer to the beginning of the data.
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{{PageSyntax}}
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:: RESTORE [datafield]
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* The datafield line label or number enables a labeled data field to be [[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|"Out of Data" error]] when reading a data field!
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* See the [[DATA]] statement for [[STRING]] data value specifications.
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* '''Do not place [[DATA]] fields after [[SUB]] or [[FUNCTION]] procedures! QB64 will FAIL to [[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:'' Restoring a labeled DATA field to avoid going past the end of DATA.
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{{CodeStart}}
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DO
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{{Cl|INPUT}} "Enter a month number(1 to 12): ", monthnum%
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{{Cl|RESTORE}} Months
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FOR i = 1 TO monthnum%
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{{Cl|READ}} month$, days% 'variables must match data field types
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NEXT
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{{Cl|PRINT}} "The month "; month$; " has"; days%; "days."
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LOOP UNTIL monthnum% < 1 OR monthnum% > 12
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Months:
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{{Cl|DATA}} January, 31, February, 28, March, 31, April, 30, May, 31, June, 30
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{{Cl|DATA}} July, 31, August, 31, September, 30, October, 31, November, 30, December, 31
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{{CodeEnd}}
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{{OutputStart}}
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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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{{OutputEnd}}
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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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''Example:'' 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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{{CodeStart}}
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{{Cl|DO}}
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{{Cl|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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{{Cl|LOOP}} {{Cl|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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{{Cl|PRINT}} "The number of relevant entries are:"; count
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{{Cl|DIM}} entry$(count) 'Now we know how many elements we need to make space for (DIM)
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{{Cl|RESTORE}} 'We restore it so that it begins reading from the first DATA again.
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{{Cl|FOR}} c = 1 {{Cl|TO}} count
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{{Cl|READ}} entry$(c) 'read the DATA and store it into the array.
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{{Cl|NEXT}}
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'we can now print the contents of the array:
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{{Cl|FOR}} c = 1 {{Cl|TO}} count
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{{Cl|PRINT}} entry$(c)
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{{Cl|NEXT}}
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{{Cl|END}}
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{{Cl|DATA}} "entry1", "entry2", "entry3", "stop"
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{{CodeEnd}}
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{{small|Code By: Cyperium}}
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{{OutputStart}}
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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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{{OutputEnd}}
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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]], [[READ]]
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{{PageNavigation}}
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