You can use the & operator to concatenate std_logic and std_logic_vector. For example, the following assignment makes a 7-bit result, where the top two bits are '1', the bottom bit is 0, and the remaining 4 are from the vector value.

y <= "11" & value(3 downto 0) & '0';

Complete the architecture below to divide the 8-bit unsigned input by 2, truncating (ignoring) any fraction. The output should also be 8 bits. Do not use the VHDL division or shift operators — instead, think about what happens when you divide a binary number by 2, and figure out how do that by manipulating bits. If it helps, think about what happens when you divide a decimal number by 10.

library IEEE;
use IEEE.std_logic_1164.all;
entity div2 is
port(
operand : in std_logic_vector(7 downto 0);
result : out std_logic_vector(7 downto 0)
);
end div2;
architecture synth of div2 is
begin
result <= x"00"; -- at least this works for 0 and 1...
end;

Are you confident about this change? (select one to recompile)