CVI - QB64 Wiki

CVI

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The CVI function converts 2 byte GET or MKI$ STRING values to INTEGER numeric values.


Syntax: CVI(2-byte string)


  • Numeric values read from a RANDOM-access or BINARY disk file must be converted from ASCII string characters back into numbers if they are to be arithmetically manipulated.
  • INTEGER values can range from -32768 to 32767.
  • CVI converts a 2-byte string created by MKI$ to an INTEGER numerical value.
  • CVL converts a 4 byte string created by MKL$ to a LONG integer numerical value.
  • CVS converts a 4-byte string created by MKS$ to a SINGLE-precision numerical value.
  • CVD converts an 8-byte string created by MKD$ to a DOUBLE-precision numerical value.
  • CV functions can only be used to convert values from MK$ string function values or data from BINARY files!


Example 1:

FIELD #1, 2 AS N$, 12 AS B$... GET #1 'GET does not need a position or variable with successive FIELD buffer reads Y = CVI(N$)

Explanation: Reads a field from file #1, and converts the first two bytes (N$) into an integer number assigned to the variable Y.
Since an integer number can contain as many as five ASCII characters (five bytes), writing a file using MKI$ conversion, and reading with the CVI conversion, as many as three bytes per number recorded are saved on the storage medium.


Example 2: How CVI converts the ASCII code values created by the MKI$ function.

SCREEN 12 '_PRINTSTRING requires a graphic screen mode DIM Q AS STRING * 1 Q = CHR$(34) ' create Print using templates to align the values returned tmp1$ = "1st character code = ### * 1 = ### " tmp2$ = "2nd character code = ### * 256 = ##### " tmp3$ = " & " tmp4$ = " CVI Total = ##### " DO COLOR 14: LOCATE 13, 20: INPUT "Enter an Integer from 1 to 32767(0 quits): ", number% IF number% < 1 THEN EXIT DO CLS ASCII$ = MKI$(number%) ' create the 2 byte character string COLOR 11 _PRINTSTRING (152, 240), "MKI$ creates 2 byte ASCII string: " + Q + ASCII$ + Q ' displays character(s) asc1% = ASC(ASCII$) ' find the ASCII code values of each character asc2% = ASC(ASCII$, 2) ' QB64 allows ASC to read specific characters in a string LOCATE 18, 20: PRINT USING tmp1$; asc1%; asc1% LOCATE 19, 20: PRINT USING tmp2$; asc2%; asc2% * 256 LOCATE 20, 20: PRINT USING tmp3$; "-----" LOCATE 21, 20: PRINT USING tmp4$; asc1% + (256 * asc2%) LOOP SYSTEM

Code by Ted Weissgerber
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" = 12345.


See also:



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