What is static member class explain
A class member declared static is a single instance of that member shared by all instances of this class (that's why it is sometimes termed a class variable, as opposed to object variable). This feature has many uses: for instance, in order to create a file lock, one can use a static bool class member. An object trying to access this file has to check first whether the static (i.e., shared) flag is false. If it is, the object turns the flag on and processes the file safely, since other objects will now find that the flag is now on, and hence -- they cannot access the file. When the object processing the file is done, it has to turn off the flag, enabling another object to access it. How is a static member created?
class fileProc {
FILE *p;
static bool isLocked; //only a declaration; see definition below...
public:
bool isLocked () const {return isLocked; }
};
//somewhere outside the class definition:
bool fileProc::isLocked; //definition; initialized to 'false' by default. Note: no 'static' here
Showing posts with label static. Show all posts
Showing posts with label static. Show all posts
What does static variable mean?
What does static variable mean?
There are 3 main uses for the static.1. If you declare within a function:
It retains the value between function calls
2.If it is declared for a function name:
By default function is extern..so it will be visible from other files if the function declaration is as static..it is invisible for the outer files
3. Static for global variables:
By default we can use the global variables from outside files If it is static global..that variable is limited to with in the file.
Static variable sample program:-
#include
main(){
int x = 0;
void funct1();
funct1();
printf("After first call \n");
funct1();
printf("After second call \n");
funct1();
printf("After third call \n");
}
void funct1()
{
static int y = 0;
int z = 10;
printf("value of y %d z %d",y,z);
y=y+10;
}output :- value of y 0 z 10 After first call
value of y 10 z 10 After second call value of y 20 z 10 After third call
Keywords:
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