![3.6 User-Defined Data Types
• user-defined data type known as class which can
be used, just like any other basic data type, to
declare variables.
• The class variables are known as objects, which are
the central focus of object-oriented programming,
class person
{
char name[30];
int age;
public:
void getdata(void);
void display(void);
};
public class Dog
{
String breed;
int age;
String color;
void barking(){ }
void hungry(){ }
void sleeping(){ }
}
9](https://image.slidesharecdn.com/oop-l3n-151004170051-lva1-app6892/85/Oop-l3n-9-320.jpg)
![Arrays, functions and pointers
• the application of arrays in C++ is similar to
that in C.
• When initializing a character array in ANSI C,
the compiler will allow us to declare the array
size as the exact length of the string constant.
E.g.:
– char string[3] = "xyz";
• in C++, the size should be one larger than the
number of characters in the string.
11](https://image.slidesharecdn.com/oop-l3n-151004170051-lva1-app6892/85/Oop-l3n-11-320.jpg)
Oop l3n
- 1. Tokens, Expressions and Control Structures Dr. Mohammad Shahidul Islam AP, IIT, JU 1
- 2. 3.2 Tokens • the smallest individual units in a program are known as tokens. • Eg: • Keywords • Identifiers • Constants • Strings • Operators • Usually program is written using these tokens, white spaces, and the syntax of the language. 2
- 3. 3.3 Keywords • They are explicitly reserved identifier and • cannot be used as names for the program variables or • other user-defined program elements. • Some examples: • If • Else • Void • Int etc. 3
- 4. 3.4 Identifiers and Constants • Identifiers refer to the names of variables, functions, arrays, classes, etc. created by the programmer. • They are the fundamental requirement of any language, • Each language has its own rules for naming these identifiers. 4
- 5. Constants • Constant refer to fixed values that do out change during the execution of a program. • They include integers, characters, floating point numbers and strings. Eg. – 123 integer const – 123.21 Floating point – “A” character const 5
- 6. 3.5 Basic Data Types • Data types in C++ can be classified under various categories as shown in Fig. 3.1, 6
- 7. Cont. • Compilers needs to support the language data types, known as basic or fundamental data types • the basic data types may have several modifiers preceding them to serve the needs of various situations. • modifiers like: ‘signed’, ‘unsigned’, ‘long’, and ‘short’ may be applied to character and integer basic/fundamental data types, 7
- 8. Fundamental data types and their ranges 8
- 9. 3.6 User-Defined Data Types • user-defined data type known as class which can be used, just like any other basic data type, to declare variables. • The class variables are known as objects, which are the central focus of object-oriented programming, class person { char name[30]; int age; public: void getdata(void); void display(void); }; public class Dog { String breed; int age; String color; void barking(){ } void hungry(){ } void sleeping(){ } } 9
- 10. Enumerated Data Type • An enumerated data type is another user- defined type which provides a way for attaching names to numbers, – enum shape(circle, square, triangle); – enum colour(red. blue, green, yellow); 10
- 11. Arrays, functions and pointers • the application of arrays in C++ is similar to that in C. • When initializing a character array in ANSI C, the compiler will allow us to declare the array size as the exact length of the string constant. E.g.: – char string[3] = "xyz"; • in C++, the size should be one larger than the number of characters in the string. 11
- 12. functions • Concept of functions has changed a lot from C to C++. • The is to cope up with the OOP. • This makes the program more reliable and readable. 12
- 13. pointers • The concept of functions has also changed a lot from C to C++. • As C++ is an OOP language, its adds the concept of constant pointer and pointer to a constant. • E.g: • char * const p1= "GOOD"; // constant pointer • char const * p1= "GOOD"; // pointer to constant 13