Detailed Description of lstrcmp and Alphabetic Characters

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.1 and 3.0

SYMPTOMS

Executing the following function in the English language returns -1, indicating that a lowercase 'e' is less than an uppercase 'Z':

   lstrcmp("e","Z");

CAUSE

lstrcmp() performs a comparison in the same manner as does a real dictionary. Characters are compared in a case-insensitive manner first, then specific details are compared (for example, lowercase versus uppercase).

lstrcmp() performs its comparisons by first setting up a primary and secondary weight. The primary weight is the value of the character after converting to uppercase. The secondary weight describes whether the character was originally lowercase or uppercase.

Using the standard ASCII table as a guide (0...9ABC...XYZabc...xyz), the following are examples of lstrcmp:

   "A" < "a" < "B" < "b"
   "Aaa" < "aaa" < "Aab"

   1. Both characters are converted to uppercase.
   2. The primary weights are compared and found equal.
   3. Because the primary weights are equal, the secondary weights are
      compared. It is then determined that "A" is less than "a"
      because "a" is higher in the ASCII chart.

   1. Both characters are converted to uppercase.
   2. The primary weights are compared and it is determined that "A"
      is less than "B" on the ASCII chart. No secondary weight
      comparison is performed.

When two characters are compared and they are equal, this is called a "collision," and "delayed comparison" will be performed using the secondary weight.

MORE EXAMPLES

   e,a  --> E,A --> E>A = 1
   e,e  --> E,E --> E=E = 0  Because they are equal, the case is
                             checked (secondary weight).
   e,z  --> E,Z --> E<Z = -1

   e,A  --> E,A --> E>A = 1
   e,E  --> E,E --> E=E = 1  Because they are equal, the case is
                             checked (secondary weight).
   e,F  --> E,F --> E<F = -1

RESOLUTION

If you need to sort by ASCII values using case sensitivity, use the C run-time function strcmp() or _fstrcmp().

Also, Far East Windows-based applications adopt this dictionary sorting technique in English and local languages.

For detailed information about the sort order used with non-alphabetic characters, accented characters, and characters in international languages, query on the following words in this Knowledge Base:

   lstrcmpi and international and sort