!head('PARAMETER statement')
the PARAMETER statement allows the programmer to create "symbolic constants".
that is, you may use what look like variable names in places where only 
constants are allowed, such as DIMENSION statements in a main program.
PARAMETER constants may be used everywhere a constant may, except for
FORMAT statements.
for example:
)l2a
	parameter (nx=10,ny=20)
	real matrix(nx,ny)
	do 10 i=1,nx
	read(5,1) (matrix(i,j),j=1,ny)
1	format(20f5.0)
10	continue
	...
	end
) !p in this case "nx" and "ny" are symbolic constants any may appear
in places (such as actual array bounds) where constants must appear.
they may also appear in expressions (such as DO loop parameters) where
integer constants may appear. since the compiler knows that PARAMETER 
names are constants it may be able to optimize certain expressions better
than if variables were used.
!head('CHARACTER variables')
there exists a new type of variable in Fortran 77, namely the CHARACTER
variable. character variables and expressions may be used to manipulate
character strings directly where various contortions had to be used to 
manipulate INTEGER or LOGICAL*1 variables as characters. for example:
)l2a
	parameter (maxcmd=5)
	character *10 cmds(maxcmd)
	data cmds/'help', 'read', 'write', 'statistics', 'stop'/
	character *10 cmd
	read(5,15) cmd
15	format(a)
	do 10 i=1,maxcmd
	if(cmd.eq.cmds(i)) go to (1,2,3,4),i
10	continue
	write(6,11) cmd
11	format('invalid command: ',a)
	stop
c
	...
	end
)
!head('#INCLUDE feature')
for convenience, (and compatability with other !un processors) this compiler
allows a special file inclusion facility. this is useful when several subroutines
make use of common data areas (usually common blocks). by having the definition
of these common blocks in only one place it is much easier to modify large
programs. the syntax of the #INCLUDE feature is:
)l2 #include "filename" !where(filename) is the name of a valid !un file.
by convention, "filename" usually ends in ".h". for example:
)l2a
c main program
#include "common.h"
	...
	end
	subroutine data
#include "common.h"
	...
	end
)
