Error 10476

In this code at the time of compilation a 10476 error shows up. The code is:

-- convertidor BCD a 7 segmentos

library ieee;

use ieee.std_logic_1164.all;

-- definicion de la entidad

entity convertidor7 is

port (A: in std_logic_vector (1 downto 0);

B: in std_logic_vector (1 downto 0);

C: in std_logic_vector (1 downto 0);

D: in std_logic_vector (1 downto 0);

adisplay,bdisplay,cdisplay,ddisplay,edisplay,fdisplay,gdisplay: out std_logic);

end convertidor7;

-- definicion de las señales de entrada / salida

architecture bolean of convertidor7 is

signal An,Bn,Cn,Dn,anda1_out,anda2_out,anda3_out,anda4_out,andb1_out,andb2_out,andb3_out,andb4_out,

andc1_out,andc2_out,andc3_out,andc4_out,andd1_out,andd2_out,andd3_out,andd4_out,andd5_out,

ande1_out,ande2_out,andf1_out,andf2_out,andf3_out,andf4_out,andg1_out,andg2_out,andg3_out,andg4_out:std_logic;

-- fin de definicion de las señales

-- inicio de programa principal

begin

An <= not A(1);

Bn <= not B(1);

Cn <= not C(1);

Dn <= not D(1);

-- a

anda1_out <= c and an; <=== this is the error

anda2_out <= An and B and D;

anda3_out <= Bn and Cn and Dn;

anda4_out <= A and Bn and Cn;

adisplay <= anda1_out or anda2_out or anda3_out or anda4_out;

-- b

andb1_out <= An and Bn;

andb2_out <= An and Cn and Dn;

andb3_out <= An and C and D;

andb4_out <= A and Bn and Cn;

bdisplay <=andb1_out or andb2_out or andb3_out or andb4_out;

-- c

andc1_out <= An and B;

andc2_out <= An and D;

andc3_out <= Bn and Cn and Dn;

andc4_out <= A and Bn and Cn;

cdisplay <= andc1_out or andc2_out or andc3_out or andc4_out,

-- d

andd1_out <= An and C and Dn,

andd2_out <= An and Bn and C;

andd3_out <= Bn and Cn and Dn;

andd4_out <= A and Bn and Cn;

andd5_out <= An and B and Cn and D;

ddisplay <= andd1_out or andd2_out or andd3_out or andd4_out or andd5_out;

-- e

ande1_out <= An and C and Dn;

ande2_out <= Bn and Cn and Dn;

edisplay <= ande1_out or ande2_out;

-- f

andf1_out <= An and B and Cn;

andf2_out <= An and Cn and Dn;

andf3_out <= An and B and Dn;

andf4_out <= A and Bn and Cn;

fdisplay <= andf1_out or andf2_out or andf3_out or andf4_out;

-- g

andg1_out <= An and C and Dn;

andg2_out <= An and Bn and C;

andg3_out <= An and B and Cn;

andg4_out <= A and Bn and Cn;

gdisplay <= andg1_out or andg2_out or andg3_out or andg4_out;

end bolean;

The error states:

error (10476): vhdl error at bcd7seg.vhd(34): type of identifier "c" does not agree with its usage as "std_ulogic" type

Could anybody help me? A do not see why

Thanks