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https://github.com/QB64-Phoenix-Edition/QB64pe.git
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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
91 lines
4.6 KiB
Plaintext
91 lines
4.6 KiB
Plaintext
The '''FIELD''' statement creates a [[STRING]] type definition for a [[RANDOM|random]]-access file buffer.
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{{PageSyntax}}
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:{{KW|FIELD}} [#]{{Parameter|fileNumber%}} {{Parameter|fieldWidth1%}} AS {{Parameter|variable1$}}[, {{Parameter|fieldWidthN%}} AS {{Parameter|variableN$}}]
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{{PageDescription}}
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* {{Parameter|fileNumber%}} is a file number used in the [[OPEN]] statement or a value from the [[FREEFILE]] function.
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* Combined size of the {{Parameter|fieldWidth%}} parameters '''MUST not exceed''' the [[LEN]] = recordsize in the [[RANDOM]] [[OPEN]] statement or a [[ERROR Codes|"FIELD overflow" error]] will occur.
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* Variables are limited to [[STRING]] types. Use [[TYPE]] instead of FIELD if you want to use numerical values.
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* Once a FIELD is defined in a statement, [[GET]] can read and [[PUT]] can write data without placeholders or variables.
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* [[LSET]], [[RSET]], [[PRINT (file statement)|PRINT #]], [[PRINT USING (file statement)|PRINT # USING]], and [[WRITE (file statement)|WRITE #]] can be used to place characters in the file buffer before a [[PUT]].
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* All field definitions for a file are removed when the file is [[CLOSE|closed]] or [[RESET]] and all strings are set to null("").
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* Do NOT re-assign a field defined variable value or use it in an [[INPUT]] statement if you want the variable to remain a field!
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''Example:'' Comparing a TYPE definition with a FIELD {{KW|STRING|string}} definition.
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Demo using a TYPE definition to create a file:
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{{CodeStart}} '' ''
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{{Cl|TYPE}} ClientType
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CName {{Cl|AS}} {{Cl|STRING}} * 30 '30 bytes
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Address {{Cl|AS}} {{Cl|STRING}} * 30 '30 bytes
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City {{Cl|AS}} {{Cl|STRING}} * 15 '15 bytes
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State {{Cl|AS}} {{Cl|STRING}} * 2 ' 2 bytes
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Zip {{Cl|AS}} {{Cl|STRING}} * 5 ' 5 bytes
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{{Cl|END}} {{Cl|TYPE}} ' total size = 82 bytes
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{{Cl|DIM}} Client {{Cl|AS}} ClientType
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RecordLEN = {{Cl|LEN}}(Client) 'find the size of each TYPE record
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{{Cl|OPEN}} "ADDRESS.DAT" {{Cl|FOR (file statement)|FOR}} {{Cl|RANDOM}} {{Cl|AS}} #1 {{Cl|LEN}} = RecordLEN
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{{Cl|RESTORE}} ClientData 'restore to start of DATA
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record = 0
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{{Cl|DO}}
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{{Cl|READ}} CName$, Address$, City$, State$, Zip$ 'read DATA
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{{Cl|IF}} CName$ = "END" {{Cl|THEN}} {{Cl|EXIT DO}}
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record = record + 1 'increment record number
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Client.CName = CName$
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Client.Address = Address$
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Client.City = City$
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Client.State = State$
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Client.Zip = Zip$
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{{Cl|PUT}} #1, record, Client 'PUT by record number
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{{Cl|LOOP}}
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{{Cl|CLOSE}} #1
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{{Cl|END}}
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ClientData:
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{{Cl|DATA}} "Bob White","104 Birdland Rd.","Bellview","PA","15236"
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{{Cl|DATA}} "Ward Cleaver","123 W. Beaver St.","Beaver","PA","15255"
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{{Cl|DATA}} "Elmer Fudd","45 Wabbit St.","Bethel Park","PA","15022"
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{{Cl|DATA}} "Wyley Coyote","33 Roadrunner Ave.","Clairton","PA","15122"
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{{Cl|DATA}} "Jim Morrison","19 Doorway Dr.","Belleview","PA","15236"
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{{Cl|DATA}} "END",0,0,0,0 '' ''
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{{CodeEnd}} '' ''
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Demo using the FIELD statement to read the file:
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{{CodeStart}} '' ''
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{{Cl|CONST}} NM = 30, AD = 30, CT = 15, ST = 2, ZC = 5 ' Define field and record lengths with constants.
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{{Cl|CONST}} RLEN = NM + AD + CY + ST + ZC
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'
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{{Cl|OPEN}} "ADDRESS.DAT" {{Cl|FOR (file statement)|FOR}} {{Cl|RANDOM}} {{Cl|AS}} #1 {{Cl|LEN}} = RLEN
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{{Cl|FIELD}} #1, NM {{Cl|AS}} CName$, AD {{Cl|AS}} Address$, CY {{Cl|AS}} City$, ST {{Cl|AS}} State$, ZC {{Cl|AS}} Zip$
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{{Cl|FIELD}} #1, RLEN {{Cl|AS}} Clist$ 'define entire record
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{{Cl|GET}} #1, 1 'GET does not need a variable to read FIELD records!
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'Read file for zip codes from 15230 to 15239 .
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{{Cl|DO}} {{Cl|WHILE}} {{Cl|NOT}} {{Cl|EOF}}(1)
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ZipCheck$ = Zip$ 'read zip codes
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{{Cl|IF}} (ZipCheck$ >= "15230" {{Cl|AND (boolean)|AND}} ZipCheck$ <= "15239") {{Cl|THEN}}
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Info$ = Clist$
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{{Cl|PRINT}} {{Cl|LEFT$}}(Info$, 30) 'read name string
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{{Cl|PRINT}} {{Cl|MID$}}(Info$, 31, 30) 'read address string
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{{Cl|PRINT}} {{Cl|RIGHT$}}(Info$, 17) 'read city, state and zip code
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{{Cl|PRINT}}
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{{Cl|END IF}}
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{{Cl|GET}} #1 'simply GET reads each FIELD record after first
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{{Cl|LOOP}}
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{{Cl|CLOSE}} #1
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{{Cl|END}} '' ''
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{{CodeEnd}}
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{{PageSeeAlso}}
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* {{KW|OPEN}}
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* {{KW|GET}}, {{KW|PUT}}
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* {{KW|LSET}}, {{KW|RSET}}
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{{PageNavigation}} |