11,1 Obyektga mo‘ljallangan yondashuv tarixi

class Derived: public Abstract {
public:
void dra>v() {cout «"Salom.";}
};
int main(void)
{
Derived d;
Abstract a; return 0;
}
Agar sof virtual funksiya hosila sinfda toiiq ta’riflanmasa, u hosila sinfda ham sof virtual boiib qoladi, natijada hosila sinf ham abstrakt sinf boiadi.
class Abstract {
virtual float g(float)=0;
};
class Derived: class Abstract
{
int f();
};
int main (void)
{
Abstract a; //xato Derived d; // xato }
Abstrakt sinflar realizatsiya detallarini aniqlashtirmasdan faqat inter- feysni ko‘rsatish uchun ishlatiladi. Masalan, operatsion tizimda qurilma drayveri abstrakt sinf sifatida berilishi mumkin: class character device { public:
virtual int open()=0; virtual int close(const char*) = 0; virtual int read(const char*, int) = 0; virtual int write(const char*, int) = 0; virtual int ioctl(int ...) ⁼ 0;
II...
};
Drayverlar character_device sinfining ajdodlari sifatida kiritilishi mumkin.
Abstrakt sinf turidagi o‘zgaruvchi yaratib boimaydi, lekin abstrakt sinf turidagi ko'rsatkich yaratish mumkin. Bu ko‘rsatkichga abstrakt sinf abstrakt boimagan turli avlodlari adresini qiymat sifatida berib, abstrakt usulga mos turli usullarni chaqirish mumkin.
Masalan, yuqoridagi polimorf telefon quyidagicha ta'riflanishi mum­kin: