Why does this code give an error if a byte contains -128 and 127 characters?

Question

Byte a = 5;
Byte b = 10;
Byte c = a+b

Answer 1

The problem occurs due to the fact that there is no instruction set to perform operation on a byte type.

byte a = 5; // variable a of byte type created 5 assigned to it.

byte b = 10; // variable b of byte type created 10 assigned to it.

byte c = a+b; // a+b is automatically promoted to integer,
// since now result of summary is integer you cannot assign integer to byte.
// This occurs as the range of int is much greater than the range of byte

In order to bypass this error use casting as follow :

byte c = (byte) (a+b);

Answer 2

why does it automatically promoted to integer? 15 is still in a range of a bye. i understand why it creates the error but not why it makes it an integer of it