Access Specifiers in C++ Programming
Access Specifiers
- Access modifiers define the access control rules.
- It is used to set boundaries for availability of members of class.
Following are the three access specifiers in C++:
1. Public
2. Private
3. Protected
| Access Specifier | Description |
|---|
| Public | It is accessible from anywhere outside the class but within a program. |
| Private | It cannot be accessed or viewed from outside the class. |
| Protected | It is similar to a private member but it can be accessed in child classes which are called derived classes. |
Preprocessor Directives
- Preprocessor directives contain special instructions which indicate how the program is prepared for compilation.
- Common preprocessor command is 'include' that tells the compiler to execute a program where some information is required from the specified header file.
- It starts with '#' character.
It can be categorize into following directives:
1. Inclusion Directives
2. Macro Definition Directives
3. Conditional Compilation Directives
4. Other Directives
1. Inclusion Directives
- Inclusion category has only one directive called #include.
- It is used to include files into the current file.
It can be used as follows:
| Directives | Description |
|---|
| #include<stdio.h> | It includes stdio.h from include folder. |
| #include<iostream> | It includes cpp class library header input output stream. Stream is an object with properties that are defined by a class. |
| #include<my.cpp> | It includes my .cpp file from include folder. |
| #include"my.h" | It includes my.h file from current working folder. |
| #include"myfolder/abc.h" | It includes abc.h file from the myfolder which is available in current working folder. |
2. Macro Definition Directives
It is used to define macros, which are one or more program statements like functions.
It includes two directives for macro definition:
1. #define : It is used to define a macro.
2. #undef : It is used to undefine a macro. The macro cannot be used after it is undefined.
3. Conditional Compilation Directives
- It is used to execute statements conditionally for debugging purpose, evaluating codes etc.
It includes following directives:
i. #if
ii. #elif
iii. #endif
iv. #ifdef
v. #ifndef
- The above macros are evaluated on compile time. Most compilers do not support the use of variables with these directives.
4. Other Directives
It includes following directives:
1. #error : If the #error directive is found, the program will be terminated.
2. #line : This directive is used to change the value _ LINE _ and _ FILE _ macros.
3. #pragma : This directive is used to allow suppression of specific error messages, manage heap and stack debugging etc.
