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The StringLength routine is used in mixed-language programming. A non-
BASIC routine uses StringLength to find the number of characters in a
BASIC variable-length string.
 
length = StringLength(string-descriptor%);
    ■ The preceding syntax is for the C language.
    ■ For C, MASM, Pascal, and FORTRAN examples, see Chapter 13,
      "Mixed-Language Programming with Far Strings" in the Programmer's Guide.
 
Usage Notes
    ■ Calls to the StringLength routine are usually made from a non-BASIC
      routine.
 
      ║ Note:  If you are not doing mixed-language programming, there is
      ║        usually no reason to use StringLength. Instead, use LEN to
      ║        find the length of a variable-length string.
 
    ■ As an example, assume that a MASM routine takes a pointer to a
      string descriptor as a parameter. MASM can find the length of the
      string data by using the following code:
 
        .model
        extrn        stringlength: far
 
        .code
        mov          ax, psdparm           ; offset of descriptor
        push         ax
        call         stringlength
 
      The length of the string is returned in AX.
    ■ For detailed instructions on mixed-language programming with strings,
      see Chapter 12, "Mixed-Language Programming" and Chapter 13,
      "Programming with Near Strings" in the Programmer's Guide.