Advantages of VHDL :

i. Executable specification

ii. Validate spec in system context (Subcontract)

iii. Functionality separated from implementation

iv. Simulate early and fast (Manage complexity)

v. Explore design alternatives

vi. Get feedback (Produce better designs)

vii. Automatic synthesis and test generation (ATPG for ASICs)

viii. Increase productivity (Shorten time-to-market)

ix. Technology and tool independence (though FPGA features may be unexploited)

x. Portable design data (Protect investment)

VHDL Code for a Full Adder

Library ieee; 
use ieee.std_logic_1164.all;
entity full_adder is port(a,b,c:in bit; sum,carry:out bit); 
end full_adder;

architecture data of full_adder is
begin
sum<= a xor b xor c; 
carry <= ((a and b) or (b and c) or (a and c)); 
end data;

Waveforms