c programming

Question

#include<stdio.h>
 main()
{
    static int a=1;
    ++a;
    printf("%d",a);
    if(a<=3)
    main();
    printf("%d",a);
    
}

output: $234444$

i m not getting how extra two 4 is coming?

Comments

Hint- After printing first 2 4's function returns to it's calling function and 2nd printf() get executed for it  too.
Draw recursion tree. You will get it.

Answer 1

Go line by line

first $a's$ value incremented & $a$ becomes $2$

then,

$printf("\%d",a); \rightarrow$ prints $2$

$if(a<=3)\rightarrow$ true

$main()\rightarrow$ at this point the stack will look like     

           

    $++a\rightarrow$ $a$ becomes $3$

    $printf("\%d",a);\rightarrow$ prints $3$

    $if(a<=3)\rightarrow true$ 

    $main() \rightarrow$    at this point stack will looks like  

                            

            $++a\rightarrow$ $a$ becomes $4$

           $printf("\%d",a);\rightarrow$ prints $4$

           $if(a<=3)\rightarrow false$ 

           $printf("\%d",a);\rightarrow$ prints $4$

         Now, at this point stack will looks like Only 1 line (last line ) left to read

        $printf("\%d",a);\rightarrow$ prints $4$

    Now, stack will looks like  Only last line left to execute

   $printf("\%d",a)\rightarrow$ prints $4$

∴ Final output will be  $234444$ .

The recursion tree will be look like:

$output \rightarrow 234444$

Comments

You made a correct recursion tree but value you have given in the RHS of first node (which is showing print 2), which is wrong , it should be print 4.

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Oh.. yes ..

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Answer updated :) :)

Answer 2

output: 234444