Incompatibile Slices in VHDL

I am learning VHDL and for first project I picked up simple Brainfuck processor. When I try to compile it, I get error about incompatibile slices. I am using EdWinXP. How do I fix my code? Are there many mistakes in my code? Is there alternative of VHDL that would be simpler for C programmer?

use ieee.std_logic_1164.all;

entity BFCPU is
 port ( 
        I0 : in std_logic; --INPUT
        I1 : in std_logic; --PROGRAM
        I2 : in std_logic; --PROGRAM READY
        O1 : out std_logic; --PROGRAM NEEDED
        O2 : out std_logic; --OUTPUT
        O3 : out std_logic; --OUTPUT WRITTEN
        O4 : out std_logic); --INPUT NEEDED
        --O5 : out std_logic); --INPUT POOLING CLOCK
end BFCPU;

architecture work of BFCPU is
  type t_Memory is array (0 to 127) of std_logic_vector(7 downto 0); 
  signal rammem : t_Memory; 
  signal pointer : std_logic;
 begin
 pointer <= 0;
 workflow: process (I2) is
 begin
  if I1=1 then
    rammem(pointer) <= std_logic_vector(unsigned(rammem(pointer)) + 1);
  elsif I1=2 then
    rammem(pointer) <= std_logic_vector(unsigned(rammem(pointer)) - 1);
  elsif I1=3 then
    pointer <= pointer - 1;
  elsif I1=4 then
    pointer <= pointer + 1;
  elsif I1=5 then
    O2 <= rammem(pointer);
  elsif I1=6 then
    O4 <= not O4;
    inwait: while( I0 = 0 ) loop
        if not (I0 = 0) then
            rammem(pointer) <= I0;
        end if;
    end loop inwait;
    O4 <= not O4;
  end if;
 end process workflow;
end work;

Solution

What you're writing below the begin statement and outside a process is always true, so this isn't sequential in any form. Imagine like an FPGA pin, which is soldered to ground.

You try to manipulate the pointer signal from within a process, but you can't because your pointer is fixed to '0'. If you want the pointer initializing to '0', as it looks like, you have to put this line within the process. However, i see you try to call arithmetic operations with the pointer signal, but you are defining the signal as std_logic. std_logic can represent '0', '1' and several other states, like High-Z, but not a number. You should take an integer or natural for calculations.