델 성경중 발췌했슴다.



You can mix long strings (AnsiString values) and null-terminated strings (PChar values) in expressions and assignments, and you can pass PChar values to functions or procedures that take long-string parameters. The assignment S := P, where S is a string variable and P is a PChar expression, copies a null-terminated string into a long string.

In a binary operation, if one operand is a long string and the other a PChar, the PChar operand is converted to a long string.



You can cast a PChar value as a long string. This is useful when you want to perform a string operation on two PChar values. For example,



S := string(P1) + string(P2); <<<<<<<<<<<<<<<<<<<<<<<<<<<< 요기



You can also cast a long string as a null-terminated string. The following rules apply.



If S is a long-string expression, PChar(S) casts S as a null-terminated string; it returns a pointer to the first character in S. For example, if Str1 and Str2 are long strings, you could call the Win32 API MessageBox function like this:



MessageBox(0, PChar(Str1), PChar(Str2), MB_OK);



(MessageBox is declared in the Windows interface unit.)



You can also use Pointer(S) to cast a long string to an untyped pointer. But if S is empty, the typecast returns nil.

When you cast a long-string variable to a pointer, the pointer remains valid until the variable is assigned a new value or goes out of scope. If you cast any other long-string expression to a pointer, the pointer is valid only within the statement where the typecast is performed.

When you cast a long-string expression to a pointer, the pointer should usually be considered read-only. You can safely use the pointer to modify the long string only when all of the following conditions are satisfied.



The expression cast is a long-string variable.

The string is not empty.

The string is unique