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67 lines
3.2 KiB
Plaintext
67 lines
3.2 KiB
Plaintext
The [[CVI]] function decodes a 2-byte [[STRING]] generated by [[MKI$]] (or read from a file) to [[INTEGER]] numeric values.
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{{PageSyntax}}
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: {{Parameter|result%}} = [[CVI]]({{Parameter|stringData$}})
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{{PageDescription}}
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* ''CV'' functions ([[CVD]], [[CVS]], [[CVI]], [[CVL]], [[CVDMBF]], [[CVSMBF]]) are used to convert values encoded by ''MK$'' functions ([[MKD$]], [[MKS$]], [[MKI$]], [[MKL$]], [[MKDMBF$]], [[MKSMBF$]]).
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* '''QB64''' has [[_CV]] and [[_MK$]] functions which can also deal with extended [[Data types|data types]].
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* [[INTEGER]] values can range from -32768 to 32767.
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* Doesn't return [[_UNSIGNED]] values.
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{{PageExamples}}
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''Example 1:''
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{{CodeStart}} '' ''
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{{Cl|FIELD}} #1, 2 {{Cl|AS}} N$, 12 {{Cl|AS}} B$...
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{{Cl|GET}} #1 'GET does not need a position or variable with successive FIELD buffer reads
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Y = {{Cl|CVI}}(N$) '' ''
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{{CodeEnd}}
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:''Explanation:'' Reads a field from file #1, and converts the first two bytes (N$) into an integer number assigned to the variable Y.
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:Since the representation of an integer number can use up to 5 ASCII characters (five bytes), writing to a file using [[MKI$]] conversion, and then reading back with the [[CVI]] conversion can save up to 3 bytes of storage space.
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''Example 2:'' How CVI converts the ASCII code values created by the MKI$ function.
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{{CodeStart}}
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{{Cl|SCREEN (statement)|SCREEN}} 12
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{{Cl|DIM}} Q {{Cl|AS}} {{Cl|STRING}} * 1
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Q = {{Cl|CHR$}}(34)
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' create Print using templates to align the values returned
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tmp1$ = "1st character code = ### * 1 = ### "
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tmp2$ = "2nd character code = ### * 256 = ##### "
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tmp3$ = " & "
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tmp4$ = " CVI Total = ##### "
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{{Cl|DO...LOOP|DO}}
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{{Cl|COLOR}} 14: {{Cl|LOCATE}} 13, 20: {{Cl|INPUT}} "Enter an Integer from 1 to 32767(0 quits): ", number%
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{{Cl|IF...THEN|IF}} number% < 1 {{Cl|THEN}} {{Cl|EXIT DO}}
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{{Cl|CLS}}
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ASCII$ = {{Cl|MKI$}}(number%) ' create the 2 byte character string
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{{Cl|COLOR}} 11
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{{Cl|_PRINTSTRING}} (152, 240), "{{Cl|MKI$}} creates 2 byte ASCII string: " + Q + ASCII$ + Q ' displays character(s)
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asc1% = {{Cl|ASC}}(ASCII$) ' find the ASCII code values of each character
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asc2% = {{Cl|ASC}}(ASCII$, 2) ' '''QB64''' allows ASC to read specific characters in a string
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{{Cl|LOCATE}} 18, 20: {{Cl|PRINT USING}} tmp1$; asc1%; asc1%
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{{Cl|LOCATE}} 19, 20: {{Cl|PRINT USING}} tmp2$; asc2%; asc2% * 256
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{{Cl|LOCATE}} 20, 20: {{Cl|PRINT USING}} tmp3$; "-----"
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{{Cl|LOCATE}} 21, 20: {{Cl|PRINT USING}} tmp4$; asc1% + (256 * asc2%)
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{{Cl|LOOP}}
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{{Cl|SYSTEM}} '' ''
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{{CodeEnd}}
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{{small|Code by Ted Weissgerber}}
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:''Explanation:'' All [[ASCII]] characters can be displayed using [[_PRINTSTRING]] . The routine gets the [[ASCII]] code, which is the actual value needed by [[CVI]]. The first byte code is always between 0 and 255. The second byte can return 0 thru 127 and CVI multiplies that value by 256. This proves that you cannot just feed a string number value to [[CVI]] and get the result desired. ("90" gets decoded to 12345).
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{{PageSeeAlso}}
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* [[MKD$]], [[MKI$]], [[MKS$]], [[MKL$]], [[MKDMBF$]], [[MKSMBF$]]
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* [[CVS]], [[CVD]], [[CVL]], [[CVSMBF]], [[CVDMBF]]
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* [[_CV]], [[_MK$]]
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{{PageNavigation}}
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