When you pass a parameter by value, it just copies the value within the function parameter and whatever is done with that variable within the function doesn't reflect the original variable e.g.
foo(a, b, c)
{
b =b++;
a = a++;
c = a + b*10
}
X=1;
Y=2;
Z=3;
foo(X, Y+2, Z);
//printing will print the unchanged values because variables were sent by value so any //changes made to the variables in foo doesn't affect the original.
print X; //prints 1
print Y; //prints 2
print Z; //prints 3
but when we send the parameters by reference, it copies the address of the variable which means whatever we do with the variables within the function, is actually done at the original memory location e.g.
foo(a, b, c)
{
b =b++;
a = a++;
c = a + b*10
}
X=1;
Y=2;
Z=3;
foo(X, Y+2, Z);
print X; //prints 2
print Y; //prints 5
print Z; //prints 52
for the pass by name; Pass-by-name