Why is default statement used in switch case in C?

goto statement is used to transfer the normal flow of a program to the specified label in the program. Below is the syntax for goto statement in C.

{
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                    <small># Tutorial: goto Statement in C</small> 
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                  <h5 class="mb-1" style="color:#194757;">650. &nbsp;What value will be assigned to the variable X if a = 10, b = 20, c = 30, d = 40 for the expression X = a/b+c*d-c?</h5>
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                     Answer: <ul>
<li>The above arithmetic operation is performed based on the precedence of the operators.</li>
<li>In above mentioned expression, c*d will be performed first. Then, a/b, then (c*d)-c, then (a/b) + ((c*d)-c).</li>
<li>Please check the operator precedence table to know the priority and associativity of the C operators.</li>
<li>Output of the above expression is 1170.</li>
</ul>
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#include <stdio.h>
#include <stdlib.h>
 
int main()
{
   int a = 10, b = 20, c = 30, d = 40, X ;
 
   X = a/b+c*d-c;
   printf(" Value of X = %d\n", X);
   return 0;
}

int X1 = 13/3;
int X2 = 13%3;

• The value of X1 is 4
• The value of X2 is 1

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.