What is volatile keyword?

It’s a pointer variable which can hold the address of another pointer variable. It de-refers twice to point to the data held by the designated pointer variable.

Eg: int x = 5, *p=&x, **q=&p;

Therefore ‘x’ can be accessed by **q.

Both allocates memory from heap area/dynamic memory. By default calloc fills the allocated memory with 0 s.

By default every local variable of the function is automatic (auto). In the below function both the variables ‘i’ and ‘j’ are automatic variables.

void f() {
int i;
auto int j;
}
NOTE − A global variable can’t be an automatic variable.

Break can appear only with in the looping control and switch statement. The purpose of the break is to bring the control out from the said blocks.

for(expression-1; expression-2; expression-3) {
 //set of statements
}

When control reaches for expression-1 is executed first. Then following expression-2, and if expression-2 evaluates to non-zero  set of statements  and expression-3 is executed, follows expression-2.

If a header file is included with in < > then the compiler searches for the particular header file only with in the built in include path. If a header file is included with in " ", then the compiler searches for the particular header file first in the current working directory, if not found then in the built in include path.

Get the two-S compliment of the same positive integer. Eg: 1011 (-5)

Step-A − One-S compliment of 5 : 1010

Step-B − Add 1 to above, giving 1011, which is -5

A static local variables retains its value between the function call and the default value is 0. The following function will print 1 2 3 if called thrice.

void f() { 
static int i; 
++i; 
printf(“%d “,i); 
}

If a global variable is static then its visibility is limited to the same source code.

Used to resolve the scope of global symbol.

Example: 
main() {
extern int j;
Printf("%d",j);
}

int j = 20;