how >> and << works

Question

#include <stdio.h>

int main(void) {
	int a=5, b=10;
	printf("%d%d",a,b);
	make_it(b,a,a+b);
	printf("%d%d",a,b);
	return 0;
}
int make_it(int x,int y, int z){
	x*=y+z;
	y=x<<1;
	z=x+y;

}

Comments

<<: Left Shift (note pointed arrow is towards left side), multiplies the number by 2 (assuming no overflow).

>>: Right Shift (note pointed arrow is towards right side), divides the number by 2

Answer 1

Answer is 5 & 10.

Inside function make_it() we are not passing address of x,y,z back to main function. So, values of x,y & z do changes but only within make_it() func...not passed to main function. Therefore values of a & b remains same.

And the values inside make_it() function are:

$x = 10*(5+15) = 200; binary(x) = 11001000; y = x<<1; binary(y) = 110010000;  i.e. y = 400; z = 200+400 = 600;$

Comments

*= is assignment operator so we will write it as x=x*(y+z)

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I have a doubt that when a expression like x*=y+z is there, we have to first compute y+z or we have to remove shortcut like x=x*y+z. Please help me

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we have operator precedence table for calculating the expression on the basis of operator precedence.We know the arithmetic operators are having heigher precedence than assignment operators,so we'll first perform y+z  and hence,  x=x*(y+z) ..so first calculate y+z  then multiply by x and put it into the x.

Answer 2

Answer will be 5, 10 and 5 , 10

At first of the C program when main will call , value of a will declare as 5 and value of b will be 10 and will print it for first time

Now, function make_it will call and passes the value b,a,a+b as value of x,y,z.

So, x=10 , y=5 , z=15

But here variable passed as call by value (not call by reference). So, x=x*(y+z) will be equal to 200

Next is a shift operation

There are two shift operation

Left Shift(<<) and right shift(>>). Shift operation done bitwise.So, we need to convert the number in binary and then have to do shift operation

Value of x is 200, and it's binary is 11001000 and if we do left shift , it will be 10010000 , which is 144

And finally z=x+y=200+144=344

But all these changes are for local variables and for function make_it() itself. So, there is no change in main() function. And that is why it will print 5 and 10 again in 2nd printf statement

Comments

I think it will depend on compiler

Not every compiler will take upto 16 bit

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but if we do it theoretically then we should consider it 16 bits

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yes, tried it

as int takes 2B or 4B, so, 16bit it could take and will print 400

https://ideone.com/y0fO9n