The reserved word is an identifier reserved in the VHDL language for a special purpose.
The reserved words cannot be used as explicitly declared identifiers. The complete list of reserved words is given below:
abs
after
alias
all
and
architecture
array
assert
attribute
begin
block
body
buffer
bus
case
component
configuration
constant
disconnect
downto
else
elsif
end
entity
exit
file
for
function
generate
generic
group
guarded
if
impure
in
inertial
inout
is
label
library
linkage
literal
loop
map
mod
nand
new
next
nor
not
null
of
on
open
or
others
out
package
port
postponed
procedure
process
pure
range
record
register
reject
rem
report
return
rol
ror
select
severity
signal
shared
sla
sll
sra
srl
subtype
then
to
transport
type
unaffected
units
until
use
variable
wait
when
while
with
xnor
xor
VHDL is case insensitive, therefore there is no difference using either uppercase or lowercase for reserved words.
If an identifier is placed between leading and trailing backslashes, it becomes an extended identifier and is no longer a reserved word (e.g. \port\ is not a reserved word).