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83 lines
3.3 KiB
Plaintext
83 lines
3.3 KiB
Plaintext
The [[DATA]] statement creates a line of fixed program information separated by commas. The DATA can be later READ by the program at runtime.
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{{PageSyntax}}
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: [[DATA]] [value1, value2, ...]
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{{PageDescription}}
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* DATA is used at the beginning of every data field line with commas separating the values that follow.
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* Values can be any '''literal''' [[STRING]] or numerical type. '''Variables cannot be used.'''
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* DATA fields can be placed and READ consecutively in the main program code body with or without line labels for [[RESTORE]].
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* DATA is best placed after the main program code.
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** '''QB64''' DATA can be placed inside a [[SUB]] or [[FUNCTION]] procedures.
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* [[RESTORE]] will only read the first data field if the DATA is not labeled or no label is specified in a RESTORE call.
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* When using multiple DATA fields, label each data field with a line label so that each data pointer can be reset for multiple reads with '''[[RESTORE]] ''linelabel'''''.
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* QBasic comma separations were flexible to allow column alignments when creating them. QB64 removes spacing between commas.
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* [[STRING]] DATA values with end spaces, QBasic keywords and values that include the comma character must be enclosed in quotation marks.
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* DATA fields can only be created by the programmer and cannot be changed by a user or lost.
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* Comments after a data line require a colon before the comment.
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* If a [[READ]] statement attempts to read past the last data value, an [[ERROR Codes|"Out of Data" error]] will occur. Use end of data markers when necessary.
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* '''[[DATA]] fields can be placed after [[SUB]] or [[FUNCTION]] procedures, but line labels are not allowed.'''
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{{PageExamples}}
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''Example 1:'' Creating two DATA fields that can be [[READ]] repeatedly using [[RESTORE]] with the appropriate line label.
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{{CodeStart}} '' ''
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{{Cl|RESTORE}} Database2
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{{Cl|READ}} A$, B$, C$, D$ 'read 4 string values from second DATA field
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PRINT A$ + B$ + C$ + D$ 'note that quoted strings values are spaced
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{{Cl|RESTORE}} Database1
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FOR i = 1 TO 18
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{{Cl|READ}} number% 'read first DATA field 18 times only
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PRINT number%;
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NEXT
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END
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Database1:
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{{Cl|DATA}} 1, 0, 0, 1, 1, 0, 1, 1, 1
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{{Cl|DATA}} 2, 0, 0, 2, 2, 0, 2, 2, 2 : ' DATA line comments require a colon
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Database2:
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{{Cl|DATA}} "Hello, ", "world! ", Goodbye, work! '' ''
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{{CodeEnd}}
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{{OutputStart}}Hello world! Goodbyework!
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1 0 0 1 1 0 1 1 1 2 0 0 2 2 0 2 2 2
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{{OutputEnd}}
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''Example 2:'' How to [[RESTORE]] and [[READ]] DATA in a [[SUB]] procedure in QB64. Line labels can be used for multiple DATA fields.
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{{CodeStart}} '' ''
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{{Cl|DIM}} {{Cl|SHARED}} num(10) 'shared array or must be passed as a parameter
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ReadData 2 '<<<<<<< change value to 1 to read other data
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{{Cl|FOR...NEXT|FOR}} i = 1 {{Cl|TO}} 10
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{{Cl|PRINT}} num(i);
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{{Cl|NEXT}}
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{{Cl|END}}
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{{Cl|SUB}} ReadData (mode)
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{{Cl|IF...THEN|IF}} mode = 1 {{Cl|THEN}} {{Cl|RESTORE}} mydata1 {{Cl|ELSE}} {{Cl|RESTORE}} mydata2
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{{Cl|FOR...NEXT|FOR}} i = 1 {{Cl|TO}} 10
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{{Cl|READ}} num(i)
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{{Cl|NEXT}}
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mydata1:
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{{Cl|DATA}} 1,2,3,4,5,6,7,8,9,10
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mydata2:
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{{Cl|DATA}} 10,9,8,7,6,5,4,3,2,1
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{{Cl|END SUB}} '' ''
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{{CodeEnd}}
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{{OutputStart}} 10 9 8 7 6 5 4 3 2 1 {{OutputEnd}}
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{{PageSeeAlso}}
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* [[READ]]
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* [[RESTORE]]
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* [[SUB]], [[FUNCTION]]
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{{PageNavigation}}
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