Help to compile FORTAN code for an Homeogenous slab shielding problem. The code is listed below which will not compile.

$----------------------------------------------------------------$

$1.$ The number of trials run.

$2.$ The thickness of the slab.

$3.$ The value of the total macroscopic cross section.

$4.$ The value of the macroscopic absorption cross section.

$5.$ The fraction of particles that were absorbed in the slab.

$6.$ The fraction of particles that penetrated the slab.

$7.$ The fraction of particles that backscattered out of the slab.

$8.$ The sum of the three fractions, that is$,$ items $5,6$ and $7.$

$---------------------------------------------------------------$

program infiniteslab

$!..$ Provides the file I$/$O shell for the Monte Carlo infinite slab project

$!..$ Format$-$free read of data for 'ncase' cases from fort$\mathrm{.}100$

$!..$ Writes formatted output to fort$\mathrm{.}101$

$!..$ Compilation command

$!..$ gfortran $-$o infslab.exe infiniteslab.f$95-$static ranseed.f$95$

implicit none

$!..$ ncase $-$ number of cases to run $($user input$)$

$!..$ ntrial $-$ number of particles $($trials$)$

$!..$ sigt $-$ total macro xsec$,1/$cm

$!..$ siga $-$ absorption macro xec, $1/$cm

$!..$ thick $-$ shield thickness, cm

$!..$ tprob $-$ sum of the output probabilities

$!..$ fabs $-$ fraction absorbed

$!..$ fback $-$ fraction backscattered

$!..$ fpen $-$ fraction penetrated

integer :: ncase, n$,$ ntrial $=10000$

real :: sigt, siga, thick, tprob, fabs, fback, fpen

$!..$ Store run title enclosed by single quotes

$!..$ Should include student name

real :: r $!..$ random number between $0$ and $1$

integer :: d$,$ i$,$ x $!..$

real :: theta $!..$

real, parameter :: pi $=3\mathrm{.}1415926536$

character$($len$=80)$ :: title

$!..$ add additional declaration statements here

$!..|$

$!..$ V

call ranseed

$!..$ read input file fort$\mathrm{.}100$

read$(100,*)$ title $!..$ store run title

read$(100,*)$ ncase $!..$ read number of cases

read$(100,*)!..$ Skip file description

$!..$ inititalize outputs

tprob $=0.$ ; fabs $=0.$ ; fback $=0.$ ; fpen $=0.$

$!..$ write output to fort$\mathrm{.}101$

write$(101,*)$ title

write$(101,50)!..$ write header line

$!========================================================================$

$!..$ run 'ncase' cases each of 'ntrial' trials

outer: do n $=1,$ ncase

$!..$ read next line of data from the input file

read$(100,*)$ ntrial, thick, sigt, siga

middle:do i $=1,$ ntrail

$!..$ insert infinite slab algorithm here

$!..|$

$!..$ V

call random$\_$number $($r$)$

d $=-$log $($r$)/$ sigt

x $=$ x $+$ d

call random$\_$number $($r$)$

theta $=2*$pi$*$r

x $=$ x $+$ dcos$($theta$)$

call random$\_$number $($r$)$

if $($ r $=1.$E$-6)$ r $=1.$E$-6$ then $!..$ ensure r not zero

d $=-$log$($r$)/$ sigt

if $($x $>=$ thick$)$ then

fpen $=$ fpen $+1$

cycle middle

call random$\_$number $($r$)$

if $($r $<=$ siga $/$ sigt $)$ then

fabs $=$ fabs $+1$

cycle middle

inner: do

call random$\_$number $($r$)$

d $=-$log $($r$)/$ sigt

x $=$ x $+$ d

call random$\_$number $($r$)$

theta $=2*$pi$*$r

x $=$ x $+$ dcos$($theta$)$

call random$\_$number $($r$)$

if $($ r $<1.$E$-6)$ r $=1.$E$-6$ then $!..$ ensure r not zero

d $=-$log$($r$)/$ sigt

if $($ x $>$ thick $)$ then

fpen $=$ fpen $+1$

cycle middle

if $($x $<0)$ then

fback $=$ fback $+1$

cycle middle

end if

call random$\_$number $($r$)$

if $($r $<$ siga$/$sigt$)$ then

fabs $=$ fabs $+1$

cycle middle

end do middle

end do outer

$!..$ write output for present case to fort$\mathrm{.}101$

write$(101,51)$ n$,$ ntrial, thick, sigt, siga, fabs, fpen, fback, tprob

$!========================================================================$

r $=$ log$(1.$E$-36)$

$!..$ FORMAT statements describe the manner in which data is to be written to file

$50$ format$(\text{'}$ Case # Trials Slab cm Sigt Siga Pabs Ppen $\text{'},$&

'Pback Totalprob'$)$

$51$ format$(\text{'}\text{'},$I$4,2$X$,$I$8,1$X$,$F$8\mathrm{.}2,1$X$,2$F$8\mathrm{.}3,4$F$8\mathrm{.}4)$

end program infiniteslab