Fortran Programming Tutorials (Revised) : 019 : Nested do loops; labels Video Lecture | Introduction to Fortran Programming (Basic Level) - Database Management

hello guys my name is Aaron and welcome
to my channel this series is a series of
tutorials on photon programming now if
you guys noticed we were in the last
program we were the last video we were
continuing about we were doing a program
called a successive factor is using
nested two loops and we stopped here
okay and this this is actually a direct
continuation of that video okay let's
begin this video let's start let's start
straight away No
now what advantage of photon and other
programming languages that they allow
you to dial are you the operation of
nested they all of you the nested
operations meaning you can place a loop
or a condition statement inside another
loop or another distance statement and
mix and matching Li for instance I am
writing this entire stuff and do loop ok
the entire thing in do loop and inside
this do loop I can invoke another do
loop ok and then you know end it here
and inside this do loop what I can do is
that I can I get inside out of the one
to loop and end it and close another to
look like this so what happens is that
inside this do loop I can insert another
do loop and inside this I can do another
loop de loop so this is like this is
what you call as nested loop nested
feature nested looping okay one loop
inside the other and this kind of nested
feature
looping is actually pretty much
essential when you guys do something
like matrix averaging matrix
multiplication or dot product
formulation and stuff and so on okay as
of now we don't need this I third the
loop you just need to only to LA two of
it so that's big in here in this in the
for this do loop you again need a
nitrate our variable just like what we
have above and this I trade a variable
this and this I with a variables J and
this values changes between I I mean one
to I not n but one to I okay and now
inside what I will press what I'll do is
that I you know that I will increment
the I will change the fact value and I
said set it equal to fact into J
fact equals fact into J now what now
what this happens is that this world in
this will multiply they get already
given value F at the fact with J and
then stores that new way update value to
the original value as like this for
hence this is how this is how it goes
now I will explain you guys a little
clearly while how the factor is going on
now
you guys notice factorial is actually
the consecutive multiplication of n
integers for an nth number so four six
is a can take until you do
multiplication of n into n six integers
from the beginning okay
now this is how the program goes okay up
to here up to here
the program is defying you just define a
few variables you get the value at the
end and that's it now this constant on
this do loop okay
initially the do loop starts with I
equals one okay and we go inside and the
way our factors are sent to one and then
we go into this new loop in this do loop
J is initially I send us one okay with J
being one factors one we go inside and
there's this one condition only one
statement here now a fact equals fact
into J now factors one and this J is 1
so 1 into 1 times 1 is 1 and this one
stores here and this I trash it ends now
I get incremented by a neck I guess
increment to Jay gets increment to the
other value - but is this 2 greater than
1 yes so this this do loop breaks this
do loop breaks and it can and this do
loop brace and this this comes another
loop and the next value what happens is
that I get incremented by 2 I increments
by 1 value and I becomes 2 and then
checks whether the I is greater than Y n
greater than Y n and if not it will goes
and again the fact is reassign the value
1 and the staffs is to loop again and
this in this do loop J starts from 1
okay because this group this group
terminated and it's restarting so J
equals 1 and this time J values lie
between 1 and 2 so so this loop will
execute twice so J equals 1 and it goes
inside fact the fact has already said
two ones
1 times 1 is 1 it goes like this and
cease and it comes here and then goes
back now J equals 2 is still less than
or equal to I yes it is so it goes again
now what happens is that a fact is all
because of the previous ayah iteration
fact is said to be said to be 1
ok now J is 2 so J time 1 times 2 is 2
and this 2 is getting stored and the
fact becomes 2 from 1 fat becomes 2 and
after this I get incremented by 1 value
and it's 3 well since this is 3 is
greater than the I this loop breaks and
comes out and then now here I get
incremented to the value 3 3 and now
with I being 3 factor set - 1 factor set
as 1 and J J's resetting this do loop J
this this do loop is reset and its it
now with a values of J will range from 1
2 3 1 2 will be 1 2 & 3 so this loop
will run thrice for therefore the first
iteration J factus 1 J is 1 so you get
the fact to be 1 and the store gets
stored here the second addition J
becomes to practice 1 J is 2 so 1 times
2 is 2 and it gets stored here and the
third iteration J is 3 so because of the
previous hydration factors to indict J
value is 3 so 2 2 times 3 is 6 and 6
gets stored here and with that with that
this loop breaks and comes out this loop
braixen comes out and so on and so forth
and so on and so forth and this
continues up till the until ji becomes I
becomes you know equal to en after the
after the iteration with I equals and
does okay the I loop I will get
increment to a value higher than n by 1
unit and then this entire loop breaks
and we come out and that being said the
factorial if you guys notice is nothing
but the fact here so about order notice
the factorial factorial of I factorial
of I is actually nothing but the number
is
okay I'm a fact now you feel like if you
guys don't believe me watch okay I
compiled this compile this and I build
this and I execute this let me just
enter the value Phi perfect the
factorial of 1 is 1 the factor loves to
is to a total of 3 is 3 3 6 the
batterers first one 2024 and that a Phi
is 120 as simple as that
and it works fine perfect now you guys
notice I told that when I gets
incremented to a value greater than n
okay the loop breaks down now to prove
you guys that the loop does break down
let me just print the value of I here
print the star comma I equals this use a
small light I equals I know if I just
compile this build this and execute this
okay I just stopped by okay now if you
guys notice I is indeed six so this this
into increment happens six times let's
see from the value it happens kind of
five times okay to start the start with
and that's it that is it you guys think
you guys have come successfully
completed your successful factorial
program you know the last thing before I
end this program is that I want to tell
you guys about labels but I think this
is getting a little too long and I'll
tell about labels in the next tutorial
and that's a very that's a very short
one of it and then we'll go jump into
the switch case statement and then we'll
jump into some other important features
of the program okay thank you guys for
watching see you guys next tutorial bye