about keyword void in C language

[akshatha kini]

what is the purposes of the keyword void?where is this keyword is used?

[weaknessforcats]

All void means is "no type".

So this:

int var = func();

where func is:

void func();

will never work because func is "no type". Therefore no value can be assigned to var.

You see, when you call a function it becomes an instance of its return type so

int func();

tells the compiler that if func() is called it will result in an int which can be assigned to var. So this is safe:

int var = func();

but

void func();

means that func will result in "no type" so an assignment to var is invalid.

Then there's

int func(void* arg);

where func can take an argument of anything and the function will work. In C functions must have unique names. If arg can be a pointer to a double or an int you can't have:

int func(int* arg);
double func(double* arg);

You would need:

int func-int(int* arg);
double func-double(double* arg);

If there were 30 types func needs to handle you would need 30 functions. So this is the usual solution:

int func(void* arg, unsigned int argtype);

The argtype can be used inside the function to typecast arg to the correct type. Now you need only one function.