What is the value assigned to the following variables? int X1 = 13/3; int X2 = 13%3;

Storage class of all variables are auto by default unless we specify a variable is register or static or extern in C program.

• Both auto variable and register variable are local variables. Register variables are stored in register memory. Whereas, auto variables are stored in main CPU memory.
• Register variables will be accessed very faster than the normal/auto variables since they are stored in register memory rather than main memory.
• But, only limited variables can be used as register since register size is very low. (16 bits, 32 bits or 64 bits)

• Both auto and static variables are local variables.
• Static variables can retain the value of the variable between different function calls.
• But, scope of auto variable is within the function only. It can’t retain the value of the variable between different function calls.

• Type cast function should not be used in const and volatile declaration.
• Because, constant value can’t be modified by the program once they are defined.
• And, volatile variable values might keep on changing without any explicit assignment by the program as operating system will be modifying these values.

• Any number of arguments can be passed to a function. There is no limit on this. Function arguments are stored in stack memory rather than heap memory. Stack memory allocation is depending on the operating system.
• So, any number of arguments can be passed to a function as much as stack has enough memory. Program may crash when stack overflows.

All functions are global by default in a C program/file. But, static keyword makes a function as a local function which can be accessed only by the program/file where it is declared and defined. Other programs/files can’t access these static functions.

• atexit() function can be used if we want to execute any function after program is terminated normally.
• Syntax: int atexit (void (*func)(void));
• The function “func” will be called automatically without any arguments once program is terminated normally.

• exit() function terminates the program/process normally and returns the status code to the parent program/process.
• Syntax: void exit(int status)

• exit() is a system call which terminates current process. exit() is not an instruction of C language.
• Whereas, return() is a C language instruction/statement and it returns from the current function (i.e. provides exit status to calling function and provides control back to the calling function).

#define is a pre-processor directive which is used to define constant value. This constant can be any of the basic data types.