How does this assigning of variables work?

Question

int main()
{
    int x=7,z;
    int y=8;

    z=x,y;
    printf("%d",z);
}

Why are we getting 7 as result

Answer 1

The comma operator , evaluates its left operand, discards the value, and uses the right operand as the result of the operator. However it also has the lowest precedence, lower even than the assignment operator =. So this:

z=x,y;

Parses as:

(z=x),y;

So in this expression, z gets assigned the value of x which is 7. That value, being the left operand of the comma operator, gets discarded and the value of y is evaluated. The final value of the expression, 8, then gets discarded as well as it is the final value of an expression statement.

Had you done this:

z=(x,y);

Then the comma operator would evaluate to the value of y which is 8, then that value would get assigned to z.

Answer 2

int x, z; declares both x and z as integer variables. By adding the x=7 you're simply initializing it. In a similar vein, z=x sets z to the value of x. The y in that statement does nothing.