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Types of variables in C++

21 September, 2018

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C++ Local Variables

The variable declared inside function is called local variable in C++
  • Memory for this variable is allocated on execution of function and after completion of function
  • The scope of this variable within function
  • Local variable are called auto variable.
  • Auto is storage class and variable is never declared without class
  • Storage class define scope life time and storage of variable.
Example #include<iostream.h> void main() { int x; int Y; int Z; Cout << X << endl; cout<<Z<<endl; } o/p : The output of above program is garbage value, Because local variables are not given any default values.
  • C++ allows to declare local variable anywhere within function
Example # include <iostream.h> void main() { int n1; cout<< “\n input n1 value”; cin >> n1; int n2; cout<< “\n input n2 value”; cin>> n2; int n3; n3=n1+n2; cout<< “\n sum is ” << n3 } os void main() {
  • C++ allows to declare block level variables.

C++ Block level variables

The variables which are declared inside the anyone of the following block is called as Block level variables in C++
  1. Anonymous block
  2. Conditional block
  3. Iterational block
Example if(<condition>) { int x;    - > block level } Conditional Block while(<condition>) { int y;          Block level } Iterational block Example # include <iostream.h void main() { char name[10]; int sub1,sub2; cout<<”\n input name”; cin>> name; cout<< “\n input two subjects”; cin>> sub1 >> sub2; cout<< “\n input two subjects”; cin>> sub 1>> sub 2; cout << “\n name” << name; if(sub1>=40 && sub2 >=40) { int total = sub1+sub2; flat avg=total/3; cout<<”\n Total” << total; cout<< “\n Avg” << avg; cout<< “\n Result is pass”; } else cout<< “\n result fail” }
  • C++ allows to declare local and block level variables with same name
  • This is called as hicling
 

Program

void main () { int x=10; int y=20; cout<<”\n local variable x=”<<x    10 cout<<”\n local variable y=”<<y; 20 { int z=30; cout<< “\n Block local variable z=” <<Z; 30 int x=40; cout<<”\n Block local variable=” <<x; cout<<”\n block variable y= <<y”; } }
  • we can’t access local variable within Block
 

 C++ Global Variables

  • The variable declare outside the function is called global variable in C++
  • Variable is declared at global to share data between one or more than one function
  • These are called external variables.
  • Extern is a storage class
Syntax : int x; - > global variable void main() { int y; - > local variable if(<condition>) { int z; block level variable }   Screenshot_4  
  • global variables memory is allocated on loading of the program.
  • global variables are given default value
  • if global variable is int, double, float then default value is zero.
  • c++ allows to declare local and global variable with same name.
  • used in c++ 1) ::  (scope resolution)
  • pointers belongs to c++ 2) * (pointer to member access)
3  *(pointer to pointer member access operator)
  • Why we used scope resolution operator ?
  • It is a binary operator and it also work as unary operator