Help me explain the code and how the output come up. Thank you

Question

Please help me explain a C languange source code
https://code.sololearn.com/cFOr5FrXsA0H/?ref=app

Answer 1

a=1; b=2; c=3;
trace(&a,&b,c); this is calling function trace with passing addresses of a,b and passing value of c.
in the function x stores a address ( *x = &a ), and y stores b address. z stores c value so then

*x = 1, *y = 2 , z = 3
int t; // creates new variable t of type int

z+= *x; // z = z + *x => 3+1= 4 => z = 4;

*x= *y+z; // *x = 2+4 = 6 => *x = 6

t=z; // t = z => t = 4

z=*y; => z = *y => z = 2

*y=*x; => *y = 6

*x=t; => *x = 4
so finally *x = 4, *y = 6, z = 2
=>in back to main => a=4,b=6,c=3

printf("%d %d %d\n", a, b, c); // 4,6,3

// this works same , on returns calculation of
trace(&a, &b, c); // You can trace now

*x = 4, *y = 6 , z = 3
int t; // creates new variable t of type int

z+= *x; // z = z + *x => 3+4= 7 => z = 7;

*x= *y+z; // *x = 6+7 = 13 => *x = 13

t=z; // t = z => t = 7

z=*y; => z = *y => z = 6

*y=*x; => *y = 13

*x=t; => *x = 7
so finally *x = 7, *y = 13, z = 6
=>in back to main => a=7,b=13,c=3

printf("%d %d %d\n", a, b, c); // printing values..

Answer 2

Where is your doubt? Can you add your understandings..!?

trace(a, b, c) ; are just passing values. It is pass by values. Changes in the values of parameters in the function don't reflect back on original passed parameters.

trace( &a, &b, c) ; here &a returns the address of variable a so passing variable address instead of value and storing it in a pointer *x in function so changes in *x will reflect back on variable a . It is pass by reference method.

Look at first 2 calls :
trace(&a, &b, c) ; // changes reflect on a, b but not on c.
3rd call :
trace( &c, &b, a) ; changes in c, b in function will reflect back but not on a.

if anything not understood then mention that specifics....
hope it helps...

Answer 3

I'm only a beginner so I don't fully understand the code like the first function has the output of 4 6 3 and I don't understant how it became like that. Can you please eleborate your explanation. Thank you