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Can static variables be declared in a header file?
You can't declare a static variable without defining it as well (this is because the storage class modifiers
static and extern are mutually exclusive). A static variable can be defined in a header file, but this would cause each source file that included the header
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Which header file is FILE declared in?
The FILE type is declared in stdio.h.
Why static variables in a function have global extent?
A variable declared static outside of a function has a scope the of the source file only. It is not a global variable. A variable declared outside of a function and without the static qualifier would be a global variable.
Static variable in c plus plus?
There are two uses for a static variable in C++. When declared outside of a class, a variable is regarded as being global. However a static variable is deemed local to the file in which it is declared. That is, the variable is scoped to the file, and cannot be accessed by code outside of that file. This aspect was inherited from C. C++ also allows static variables to be declared inside a class. In this case, the variable is local to the class. By contrast, instance variables (non-static member variables) are local to each instance of the class. With static variables, there is only one instance of each variable which can be shared by all instances of the class. It is not unlike a global but it is scoped to the class. Since all static variables are instantiated at compile time, they exist for the entire duration a program runs. Even if they fall from scope, they never lose their value. Static variables defined within a class are also available even when no instances of the class are instantiated. Their visibility outside of the class is dependent upon whether they are declared public, protected or private.
What are Static variables in c?
A static variable in C is a variable whose value and memory allocation persists throughout the execution of the program. If the variable is declared at file scope (outside of any blocks) the static attribute means the variable is visible only to the file containing it, i.e. it can not be referenced through an extern reference in a different file.
What are the different storage class in c?
The four storage classes in C are: automatic, static, external and register. Note that storage classes are not classes in the object-oriented programming sense, they simply define the scope (visibility) of a variable.Automatic Variables (auto)All local variables are automatic by default so we seldom see the auto keyword in code. Local variables are variables declared at function scope.Static Variables (static)All global variables are static by default. Global variables are variables declared at file scope (outside of any function). Static variables can also be explicitly declared inside functions to override the default automatic storage class. All static variables, whether global or local, are allocated within the program's data segment (static memory) and do not fall from scope even if declared locally. All static variables are initialised to zero by default.It's best to avoid the use of global variables unless they are declared constant (const) as it can be difficult to keep track of all the places where a global variable is being operated upon (accessed or assigned to). This can lead to data races in multi-threaded applications unless we take steps to synchronise all access and assignment operations upon the variable. For that reason it's best to keep variables as localised as possible, passing arguments into functions whenever we need to cross scopes. Non-constant global variables should really only be considered if they truly represent a global concept within the file in which they are declared.External Variables (extern)External storage can only be applied to a global variable declared outwith file scope. That is, when a global variable is declared in one file, any external file can gain access to that same global variable simply by declaring the same name and type but with external storage. It follows that external variables are also static variables and is the only case where a variable has two storage classes. Note the local static variables (including local constant variables) cannot be declared external, they are local to the function in which they are declared.This is another reason why it is best to avoid using too many global variables. While we can generally keep track of which code can access a global variable at file scope we have no means of limiting access from outwith that file. Again, prefer local variables to global variables whenever possible.Register Variables (register)A register variable is a variable that we wish to allocate to a CPU register rather than in RAM. Register variables must be no larger than the word-length of the machine and should only be used when we explicitly require fast access to the variable, such as loop counters, accumulators and pointer variables. Note that CPU registers have no address (no identity we can refer to) so we cannot use the unary '&' operator to take the address of a register variable. This means we cannot use pointers to refer to them indirectly which, in turn, means we can only pass them to functions by value (not by reference). However, to do so would defeat the purpose of using the register storage class.Given the limited number of registers available, there is no guarantee that a register variable will actually be allocated to a register; the register keyword is merely a hint to the compiler. It should be noted that modern compilers are extremely good at optimising code so there is seldom any need to explicitly declare register variables.
Can static variables be declared in a header file in C programming?
Yes (but usually it is a bad idea).
Which header file is FILE declared in?
The FILE type is declared in stdio.h.
Scope of static variables?
Scope of static variable is with in the file if it is static global. Scope of static variable is with in the function if variable is declared local to a function. But the life time is throughout the program
Can you declare a static variable in a header file?
Yes.
Why static variables in a function have global extent?
A variable declared static outside of a function has a scope the of the source file only. It is not a global variable. A variable declared outside of a function and without the static qualifier would be a global variable.
Static variable in c plus plus?
There are two uses for a static variable in C++. When declared outside of a class, a variable is regarded as being global. However a static variable is deemed local to the file in which it is declared. That is, the variable is scoped to the file, and cannot be accessed by code outside of that file. This aspect was inherited from C. C++ also allows static variables to be declared inside a class. In this case, the variable is local to the class. By contrast, instance variables (non-static member variables) are local to each instance of the class. With static variables, there is only one instance of each variable which can be shared by all instances of the class. It is not unlike a global but it is scoped to the class. Since all static variables are instantiated at compile time, they exist for the entire duration a program runs. Even if they fall from scope, they never lose their value. Static variables defined within a class are also available even when no instances of the class are instantiated. Their visibility outside of the class is dependent upon whether they are declared public, protected or private.
What are Static variables in c?
A static variable in C is a variable whose value and memory allocation persists throughout the execution of the program. If the variable is declared at file scope (outside of any blocks) the static attribute means the variable is visible only to the file containing it, i.e. it can not be referenced through an extern reference in a different file.
Difference between header file and library file?
A header file is normally used for declarations to provide an interface that can be included into a source file that wants to use the functions/variables that have been declared. If the header file contains function prototypes, it will usually have a corresponding source file that defines the functions. /* example.h */ #define bTRUE 1 #define bFALSE 0 typedef int BOOL BOOL bEvenNumber(unsigned int uiNumber); /* example.c */ #include "example.h" BOOL bEvenNumber( unsigned int uiNumber) { return (uiNumber & 1) ? bFALSE : bTRUE; }
What happen if you declare a global variable as static in C language?
When declared as static, the variable has internal linkage and its scope is restricted to the *.c file in which it is declared. It becomes visible to all functions within the file where it is declared and not to functions in other files.
Why static data members are not initialized in member function?
Static data members are local to the class in which they are declared. That is, they are shared amongst all instances of the class, unlike instance variables where each instance has its own set of variables. In addition, static data members are also accessible to static member functions, even when no instances of the class actually exist. So if static data members are accessible even when no instance exists, how are we to initialise them? A member function is no use because that would require an instance. And a static member function isn't an option either because then the onus is upon the user to ensure that the method is called BEFORE any instances are created, which completely destroys the encapsulation of the class (not to mention the fact a static member function would require a local static variable in order to determine if it had already been called or not). The simplest solution is to initialise all static data members from outside of the class declaration. Typically we do this from within the class CPP file however we can also do it in the header file, so long as it's not declared within the class declaration. As with all static variables, the initialisation statement is executed at compile time, thus ensuring the member is fully initialised at runtime.
What are the different storage class in c?
The four storage classes in C are: automatic, static, external and register. Note that storage classes are not classes in the object-oriented programming sense, they simply define the scope (visibility) of a variable.Automatic Variables (auto)All local variables are automatic by default so we seldom see the auto keyword in code. Local variables are variables declared at function scope.Static Variables (static)All global variables are static by default. Global variables are variables declared at file scope (outside of any function). Static variables can also be explicitly declared inside functions to override the default automatic storage class. All static variables, whether global or local, are allocated within the program's data segment (static memory) and do not fall from scope even if declared locally. All static variables are initialised to zero by default.It's best to avoid the use of global variables unless they are declared constant (const) as it can be difficult to keep track of all the places where a global variable is being operated upon (accessed or assigned to). This can lead to data races in multi-threaded applications unless we take steps to synchronise all access and assignment operations upon the variable. For that reason it's best to keep variables as localised as possible, passing arguments into functions whenever we need to cross scopes. Non-constant global variables should really only be considered if they truly represent a global concept within the file in which they are declared.External Variables (extern)External storage can only be applied to a global variable declared outwith file scope. That is, when a global variable is declared in one file, any external file can gain access to that same global variable simply by declaring the same name and type but with external storage. It follows that external variables are also static variables and is the only case where a variable has two storage classes. Note the local static variables (including local constant variables) cannot be declared external, they are local to the function in which they are declared.This is another reason why it is best to avoid using too many global variables. While we can generally keep track of which code can access a global variable at file scope we have no means of limiting access from outwith that file. Again, prefer local variables to global variables whenever possible.Register Variables (register)A register variable is a variable that we wish to allocate to a CPU register rather than in RAM. Register variables must be no larger than the word-length of the machine and should only be used when we explicitly require fast access to the variable, such as loop counters, accumulators and pointer variables. Note that CPU registers have no address (no identity we can refer to) so we cannot use the unary '&' operator to take the address of a register variable. This means we cannot use pointers to refer to them indirectly which, in turn, means we can only pass them to functions by value (not by reference). However, to do so would defeat the purpose of using the register storage class.Given the limited number of registers available, there is no guarantee that a register variable will actually be allocated to a register; the register keyword is merely a hint to the compiler. It should be noted that modern compilers are extremely good at optimising code so there is seldom any need to explicitly declare register variables.
A function is declared in C header file When you try to implement in a c source file it is giving error?
The source file must include the header file. Beyond that we can only guess at the problem without seeing the content of the source and header files. Do not post the files here. Such questions are better handled by the many C programming forums available elsewhere on the Internet.
