Advanced Fortran Programming : 028 : Processing Files - Direct Access Files Video Lecture | Introduction to Fortran Programming (AdvancedLevel) - Database Management

hello guys my name is Aaron and welcome
to my channel this series is a series of
tutorials on advanced photon programming
now in this tutorial we'll be looking at
how to access and process files mainly
the direct access files okay the last
one we saw we saw relatively along for a
long video lecture on how to access and
work with sequential files we will be
looking at direct first today okay we
will be using the same kind of example
same example that we used last time
today in this tutorial as well okay same
as same as last time getting the roll
number name and the great of subjects of
students okay now this is simple we get
the student name the roll number grades
and stuff okay these are just some
processing really boosts that's it and
this is where the importance comes in
there opening a file called a store
start on the squat rack txt okay
unit number is given by U which is 10
okay access this access keyword is
mandatory because last time and then we
when we're working with the sequential
call okay you guys can remember okay the
default value of access parameter is
sequential so this has to be manually
made to be direct so this access keyword
this mandatory and then freckle should
be given as 43 record is raquel re CL is
actually the maximal record length okay
this has to be compulsively press this
must be compensated percent if you are
working with say direct files so that
our Achilles 43 I'll explain you guys
how this number 43 came up with al
explaining this little later so I am sad
that as you saw earlier status as we saw
earlier okay form okay this form has to
be formatted now last time we didn't
include form but here palmist mandatory
see okay guys if you guys can look at it
okay since the file is a direct access
filed the access Raquel and farm
okay the farm okay so I'll make a cash
in here the farm parameter
the phone okay the phone access access
and record okay track parameters okay
are are necessarily completely in this
open statement okay because all not only
that because of this format okay we are
also using a farm and here so the
because of which this is necessary this
is necessary and this is necessary okay
now let's see about how this number 43
comes into picture see the name is 25
letters so in when you're typing it in
the file you lock you by 25 25 spaces so
that's 25 okay they're giving for you
know four units of space for the roll
number that's four okay followed and
then two four units of space for both
the sub for every grade mark so you have
to twice that to 2 times of four so what
do you have is that 25 okay
Plus this for 29 plus this 837 okay yeah
37 and then between roll number and the
name you're giving three spaces that's
40 so three units for 40 and then we
rename and the first of the two numbers
the two grades we're giving three spaces
so that's another three so 43 so if you
guys notice this 43 is nothing but the
total width of all the value total
formatting with specified in the format
statement so that will be the width in
this length okay
now you're all your record for that
group is written so that's why this
record length records for this file for
any group is 43 okay now if you change
the formatting parameter at the if you
just change a form
a different manner then the record
length will change accordingly and I
just accordingly okay
and ignore this 24 meant for now it's
not it's not a burden
okay what do you have here is that we a
we get the total number of entries and
then using the do loop B and get the
value of roll number student name and
then grades and we are writing it and
that in the file now here in the file to
indicate that the indicate that the key
value for that M for every data group
okay we we use this keyword called as
rec okay just like we saw last time okay
I think it's better if I show you guys
the old five open threes and file yeah
see if you guys notice this is the last
this is the program we saw last time
okay did you guys notice access gives us
to sing or a sequential direct by
default of the sequential but since we
are using direct file you have to give
two accesses mandatory
crackle as compulsory with direct access
files so that's that's it and then farm
at or farm this by default it is
formatted but it's not but it's better
to you know write it write it in
specific write it by default over here
that's not a problem okay and then for
the right statement right statement the
key word rec is actually used for you
know used used for indicating the key of
the data group okay
this data that we are going to use as
reg will be the data that is used for
differentiating the different groups so
okay this is this will act as the roll
number kind of a thing that
differentiates the different data sets
or something of that sort
okay and then this is compulsory for dad
access direct the access pass so here
okay because of this while writing it
okay we had to indicate that when we
writing this entire data set they're a
group whichever you call it okay this
roll roll number rustad name workplace
either another have to be record length
okay now I said role to be recalled and
then keeping it uniform so that you know
accessing is easy and then
do is there a closet so for the writing
right the manner in which you write the
data to the file this looks similar to
that of sequential for the CS now here
comes the magic of direct access first
suppose I want to write if I want to you
know read them it's dad it's very simple
okay
I close the file here okay open the file
here set the format here right get the
data from the user and write them when
this dual write them in the file using
this you do look okay
and then close the file over here and
then here what I'm going to do is that
I'm going to check open
I mean access the direct access the file
data which has this value are no equals
10 directly now how do I do that it's
simple open the file but this time the
access is direct but the status is old
here if you see the status is replace
okay if the file is present it will be
replaced here the file should not be
replaced it should be used a siddhis so
I'm using this status old okay okay
and then I'm reading the statement and
how do you read it while reading it I
give the unit format and all that's okay
but I'm adding an another key another
extra parameter College rec equals RN
whoa
which is exactly similar exactly the
same as that of the rec statement used
in this write statement right over here
now what this does is that in here
instead of searching sequential are all
the values what this or this keyword
does is that it just goes down it just
goes into the fight such as for the no
record key
it's a record key or the key value which
is equal to that which has the same
value instead of are no and directly
fetches the data which is a very short
type and brings it back okay so if so
what happens is that that's it you don't
need a do loop and stuff and like you
don't need a do loop and stuff like here
okay
this is the you know class a program we
wrote last time unlike here where an you
just have to set this in a do loop and
extract one data after
then finally get the enter data instead
of like that you just it there's not
even hydration select axis and you get
the data and using this state using this
its construct okay we're taking a cross
verifying that these are the same and
then you're printing it that's it and
that's it okay and then if you want to
you know update the data or what if you
didn't just like what we did last thing
I have a code over here but this
apparently is not working okay there was
some there are some data distortion
issues I will explain just explain
what's going on I'm not able to explain
as to why it is happening but I'm not
but I noticed there is indeed a
distortion so I just comment this out
I'll show you guys how this works
later in Justin's in some play sometime
I'll just let me just comment this out
okay okay now if ever - okay let me
before that before we write something
I'll let me just you know come with this
out - okay come at this out yeah as of
now let's see how this writing has been
done so compile okay just says that
there are new stories but nothing
nothing to worry just compiled build
just warnings okay execute this don't
bring this within the screen okay let me
bring this within the screen okay so
there are like let's give me okay I'll
give two entries first and three will be
however rule number ten okay rule number
five
okay just my name okay to waits like
five five okay that's not a problem and
then I give another value ten and then
I'll just fight my brother's name ROM
okay just to understand and that's it
okay now if I were to open this file
okay
Stewart
apparently something else right okay to
open this it sure it should have written
this nicely but if I get this is the
file over here I get something like this
it shows something like mine there are
some opening issues and closing the
shoes off so that's odd
I'll have to verify this let me do this
thing again that we closed Jeannie and
then open this up again okay compile
build and run this compile and run this
let me see okay two entries nice I think
I messed it up over there I compile
compile build and run this okay the
number of entries is to first roll
number the spy just like that I okay
two values and then extend 3d it's like
that eight nine okay this looks fine to
open this surprisingly even with this
something is not right okay something is
not right and you know I'm just get I'm
just getting this file being corrupted
again often not sure why well let's not
sure why but if you guys notice as to
why this happens or if you guys are able
to find an answer for this to do let you
know I'm kind of you know kid and I know
I'm breaking my head on this part which
I'm not able to explain I don't know
okay and now this is being done this
part does trust me this works okay now
what I do what I do is that let me just
cut a comment this part of the code
let me just uncomment this part of the
code okay found that uncomment lines
okay yeah okay there are two compile
okay compile build and execute this let
me add two entries nothing much two
entries okay that's roll number write
phi phi phi then ten ten okay it shows
that the file writing was done reading
it virt it read out fine and then it
says that everything is going well if I
were to open this up open this file
right now still something is not right
okay what I'm having is that some reason
I have no table time so for some reason
I'm getting my file like this I'm
getting my file like this something is
not right and they not isn't getting
we're getting families are not able to
explain us to why to say whether it's
some kind of data corruption I'm not
sure but this is how it is but on the
other hand if maybe if large number of
data were added to it I think this form
this issue may not turn up okay let's
look at that a little later then what
I'm going to do is that let me let me
know include this part of this program
and show you the same for to uncover
these lines but I'm come on these lines
what these lines do with that the
toughest part of it we are just writing
a program just writing the data to the
file the second part of the program
they're searching for a data okay in
this third part of the program which
starts from here which we finish the
search and then we will be trying to
modify one of the data sets okay
and now how we open the file over here
roll number five is what we are going to
modify the row file is open over here
okay and then
the file is a directly read in one line
one line in this statement and then
we're checking this again to make sure
that these are same okay and he's our
same I said f equals one and then I get
the roll number student name and the
grades from the user write this in the
key word say write this you know write
this and then using write keyword and
then I'm printing the printer running
them okay so that being said that being
said if I were to compile this we're
still showing whether okay let me use
that and a farmer 20 yes is not this is
a nothing just a small space three space
between these two that's it
okay compile this build this and run
this okay this time let me give a large
data set let me say five entries and
then okay let me enter roll number one
and that will be my name okay let's get
set to arbitrary values like that and
then let's say roll number two and this
treatment brother's name two values okay
let this be no longer hide
okay this let me give my father shock
name and then fight to a leash like that
and then they let this roll number be
ten and this be my mother's name my
mother's maiden name and then two grades
then and then okay and then finally let
this roll of maybe twenty differentiate
well differentiated from mothers let
this name be my aunt's name prema and
then to Ali's 2020 okay now what it does
is that read the file return it and it's
open and it has no displayed the valley
display the data set for name equals ten
I mean doll number equals ten
okay and it's waiting for me to enter
the data
once I entered all the data is going to
write them on the screen let me write
them on the file before that I just
opened this fight I'll show you guys how
this looks like still there are issues
but if you guys notice there is a small
there's a smaller difference see my knee
the data corresponding to my name data
corresponding to my brother okay
the data corresponding to my father's
name the my mother's name and my aunt's
name so if you guys know this 1 2 3 4 5
all these pi data all this high data are
written but still you have a lot of the
backslash double 0 kind of kind of a
character encoding so it's some kind of
issue which is not able to know rectify
not sure why if ever but it another hand
let me see let me just see if I can open
this genie okay still it's not able to
open but something is happening okay
now if ever had to know change this I'm
going this with now I'm gonna since I've
said odd to be fight this I'm going to
change my change a third entropy is
actually they didn't River and I gave my
father's name okay so let this be fire
in sapphire Italy this p-51 and then my
like a father father's full name gonna
say Karen okay
and then and new and 350 151 okay and it
say that it has been modified because
it's written and let me that's fine okay
let me just open this file right now
okay it's still the same issue still the
same issue but if you guys notice this
data these data this data this data are
all say the data which I which I wanted
to modify it's not of it it's the same
as a new data set has been written okay
now this is something this way this is
something happening but what I'm trying
to say here is that
though the encoding is not supported
kind of thing such I put it Fortran is
able to open it up and use it there this
I tried to change with the changing the
format type record length slightly by
modifying tweaking this record and
slightly but thing is the data is there
but it looks very incomprehensible kind
of a thing okay now if you guys are able
to explain me how why is this that has
been disturbed
that as being incomprehensible like this
to see okay that will be really helpful
because I have everything breaking my
head on how to give a proper explanation
for this picture it's not working out
nice for me okay if you guys know about
this do let me know I learn from you
guys and that'll be very beneficial for
others and then just keep this on the
comment on the key you can just mail me
this or you can just write this
explanation if you guys found it on the
comment section that will be very useful
and I'll include I mean that will be
very useful for all the others to see
here so okay
and with that there with that you know
we are closing on the we're closing on
the section of direct access files okay
and if you and how to update them and
stuff okay like updating a file modified
entering and updating v by adding more
data and merging files I recommend you
follow the same kind of procedure we
used last time we mentioned the
pseudocode we mention last if this for
the same as direct access files with
little slight modification as per the
need that's it and now with that will
that access files over and before we
close on this tutorial I will just want
to mention one small topic called as
small topic regarding file Tran
regarding file processing there's this
keyword called as inquire available in
fortress ok and what it does is that it
just tells us tells us the availability
of the file the status of the files open
door open door unclosed infotrac now see
the thing is sometimes certain files
will be open by looking at the
programmer seeing the program will know
whether a certain file s
and are not closed or not whether it's
been accessed or not under process or
not yeah yeah but the problem but thing
is its it seemed that there might be
some situations where in the the phi
marin you know you do not know whether a
certain file is available or not
I let me certain file is available or
not whether a certain file is under
process or not but then it's open or not
how see let's say you have let's say
three to four of three to four people
work on some massive project and Fortran
let's say and then let's say you you
wanted to access certain data files okay
and this data file is data files are
being simultaneously accessed by
somebody else in your project okay now
what happens is that if if you are the
only person working in the project and
nobody else is working then the he will
not be that other person will not be
accessing it and you can access it
directly so no issues but if you're
trying to access a file and that person
is also accessing a file and this data
is like available to all three for let's
say all all four of you guys then what
happens is that sometimes when a data
has been accessed by other you should
not even you should not be allowed to
access it for no consistency of data
such as its density of data and there's
to stop overwriting conditions and stuff
okay for that kind of stuff to happen
what's necessary that kind of stuff to
happen and to make sure that you have a
check to know whether the other program
other program is other program is using
it or not undertake whether some other
subroutines some other routine were run
by other programs or using the files are
not or something of that sort
okay Inquirer statement is very
necessary to check like that if you're
just a single programmer this is not at
all of you so this is just a minor
conditions also may explain okay inquire
statement comes in three to four methods
okay I just explained you guys the three
methods now if you write the inquire
statement with this format with unit the
the parameters unit opened opened and
name
what it does is that see if first of all
it see it checks whether the fight with
the unit unit number 10 is available or
not if it is available okay
if it is available okay
what it does is that it checks for the
file name corresponding to the unit
number and then that file name is passed
as a string to this keyword file
underscore name okay and not a next let
you know the the file being present the
file being present okay it will check
whether the file is opened or not if the
file is opened it says this comma is
this is variable OB underscore status to
be true the file is not opened it says
this OPR has co-starred us to be false
okay and then this is one method and
then here you have another method
pattern here you give the file name the
form of unit number here you give the
file name in the farmer in the notes
direct name so what do you do
is that inquire give the name to be the
file name and strings as a string okay
and then what what it does is that if
this file is present if this file is
present okay it says this present to be
true meaning if the file is existing or
not the file is existing okay it means
it's present so this person will be set
set to true and if this is true okay
what it will do is that it will set P to
be the corresponding unit number for
that file okay this is exactly the other
way around here you give the unit number
to get the file name here you give the
file name to get the unit number and to
check whether it's present or not and
whence these are present these two are
prevents the file is present at the same
time it's unit number is given and I
will check whether the file is opened or
not if it's open it says the OPR disco
status to be true if it's not open and
set of pianos co-star has to be false
simple as that okay and then there is
this one movie barrel this is one more
way wherein you give unit to be filename
and then access to be access underscore
type and record to be length what it
does is that it checks whether this file
whether this file name
hello this file it's available or not if
it is available it was available what it
does is that it's it's access underscore
type to be the data type of the file he
says whether that direct that file is a
normal file that is whether it's it says
whether the file is a normal file or I
mean it just it's a the access
underscore type will have a string which
says whether the file is a direct file
or a sequential file and record the mean
the length here come from a variable
over here give it has the stores the
value of the length of the data set okay
here the other specifies can also be
used at videos on the top forget to get
other accessory information and this is
not oh this is not much this is not of
much importance but it's just simple
they just have you just guys can have a
look and that's it okay not not much of
a big deal okay that's all I have for
you guys in this tutorials in the next
tutorial we will be looking at an
interesting concept we'll be looking at
you know pointa data types and their
application and their small applications
and Fortran and and let's see how that
goes
that's all I have for you guys in this
little tag you guys for watching and
I'll see you guys next to tell so take
care then like