CAn any one help me in understanding these 3 lines in code from PLL??

[maheshkumar0459]

1)part0 <= (others => '0'); // What result can be achieved from above??//

2)part7 <= -(input1_buf); //Wt does this meant for??//

3)out_temp <= part0+(part1(14 downto 0)&'0')+
(part2(13 downto 0)&"00")+
(part3(12 downto 0)&"000")+
(part4(11 downto 0)&"0000")+
(part5(10 downto 0)&"00000")+
(part6(9 downto 0)&"000000")+
(part7(8 downto 0)&"0000000"); //Why shud add these all??//


Thanks in advance from Mahesh