Fortran Programming Tutorials (Revised) : 013 : Operator Precedence + Do loop Video Lecture | Introduction to Fortran Programming (Basic Level) - Database Management

hi guys my name is Aaron and welcome to
my channel this series is a series of
tutorials on photon programming now in
the last tutorial we saw this program
where and we explained how the logical
and relation operators work and today
today's tutorial we will be looking at
you know the do loop which is available
in Fortran for doing multiple recursive
operations and we will also look at the
there's a attribute - there are - the
value - the datatypes called as kind we
look at how these values how these can
be used accordingly and before that I
forgot to mention one topic in the last
time okay see even these logical
operators have a knob have a operator
precedence now what kind of operator
precedence these follow is as follows
okay remember last time in one of the
previous tutorials I mentioned that
these they have this a
PEMDAS rule of logical operations yes it
lip em - routes for operator precedence
yes and before that there is just one
more operator called as you
this stands for unary - are unary plus
for instance suppose if you write what
the unary is supper you know in a simple
terms okay suppose you write minus Phi
and all this - because gets more
preference sometimes you get plus Phi or
something this does not mean addition
well rather it means the sign of the
object sign of the value and all these
these are the unary operations okay if
in see you might in C or C++ okay this
value like this post increment operator
play post increment increment operating
decrement operator they also fall in the
unary but these are not available in
Fortran now so these are like not
applicable in Fortran okay so so they
come as they come to the highest
priority and then comes a PEMDAS like
parentheses exponents multiplication
division addition and subtraction and
after that comes your relation of
relational relational operators
relation operators and then comes your
logical operators so if you have if you
have a very complicated complicated
statement expression wherein you have
them I have these normal operations
followed by relate relation operators
and logical operators this is the order
in which they'll happen so you so it's
but it's better you guys have a clear
idea of how the operation goes by and
all okay that being said will I will
finish this this tutor is over let's
start a new tutorial to look at the do
loops I open a new file and save it now
I save my stuff here in Fortran files
okay let me create fire a folder called
us you know did I make any I'll make it
geometric I'll make a job I'll a killed
in photo College geometric because we
are going to use the geometric
progressions so geometric progressions
okay we are going to use geometric
progressions to explain our concepts so
this is I named this program as
geometric underscore product F 95 okay
so I'll write a comment here program to
demonstrate do loop-de-loops yeah
yeah geometry progression okay now now
for this let's write a program GOP I
write EG&G underscore pizza okay G
underscore prog meaning geometric
progression and then I end the program
here okay G or underscore prog okay
since I'm going to rested to all of them
two integers so I just I'm not going to
use only integer so before that the
implicit nun statement so I'm going to
use only integers so what I need is that
an initial value a and then the initial
value a and then a value are you know
the multiplier the multiplier statement
and I try to vary for the iteration
purposes I need a value I I will explain
you guys were dilation means now further
stood let's get the value of a and B
from the user
okay enter the value of a and value of
initial term a initial term a and you
know factor i and factor are okay that
will be easy to follow and in three
value i will be getting the star come on
a and i simpler simple enough now now
this is how a do statement works what a
do statement in fortran does is that
okay it does certain operations till the
till Allah nitration variable reaches a
party starts on a particular limit to an
ending limit okay now let yeah I need
okay I just need one more variable I
forgot again okay friend
print and number of terms okay
I use a read statement to get the value
in okay now I will explain what do what
do statement means what do statement
does is that okay
it starts with a deuced it starts with
the syntax will do and ends here and
whatever it's written inside between
these two these do statements okay it
will execute them okay the that execute
them the number of times the iterations
variable has to change
okay I'll add next thing here when I
give an ID when I give a condition like
I equals 1 to N what happens is that I
will vary what one step at a time okay
with one separate time so so what will
happen is that I will have values I
equals one two three okay I move the
cursor four five and so on and okay and
so on up to it reaches the value and so
it this so it will reach like that in
that being the case okay what happens is
when I equals one all the signals in
this do this do and this n do will be
repeated once next next time when I gets
incremented it becomes to the statement
repeats again when I becomes 3-2 pitch
again and when I equals four this
repeats again and when I equals Phi this
repeats again so until so what happens
is that this entire state whatever all
the settings are given we didn't do an
end to stay into comment lines will get
repeated in this example n times okay
but n times any and when during each of
these repetitions the value of Phi will
remain constant for one that repetition
but in the other repetition the value
will change okay and this repetition of
say the same statements mean if you guys
notice if you guys if you can follow all
the statements will that will be written
here will be written only once but
they'll perform a different
set of values different set of execution
or do different set of operations based
on the value of I okay
we have to program you have to give the
course in such a manner that for each
value if I they do a lightly different
job and all okay so that's how this goes
that's how this goes okay now you guys
understand little more clearly well when
we start doing the program okay now let
me remove this off okay now I all I have
is I don't have any print state I just
set this value to zero okay
print star comma star comma the
okay the valley okay I'll write the
value one value I of the series is okay
and then I write a into R power a into R
power I let me just put this in
parenthesis so that if you guys don't
get confused and that's it and that's it
now what we'll do it'll just print up
all the values of the rosamma trick
prohibition from the I equals 0 to 1
when I equals 0 it will print the 0th
value that will be the initial value so
ei will be it will print the value 8 the
next operation model does this it will
multiply a with R raised to 1 okay so
what will print is here so that will be
the first term okay first them and then
in the next term it will print a R
square since I becomes 2 in third thumb
yeah becomes I I becomes 3 so it will
print at the a I power 3 and so on since
if we give n will print n times so if
now there aren't any errors here so I
compile this bill this and execute this
it will ask for the value Y and I let me
give her you start with say 1 okay
and the let me get a vector to the
conventional geometry progression okay
and it's asking in the number of terms I
will give 10 terms
watch the value 0 of the series is 1 the
value 1 value 1 of the series is to the
value 2 of the series is for the value 3
of the series is 8 like that so what
just happen is because of the because of
the height rating variable I didn't
variable different output results are
getting to displayed and all ok this is
like this is very much useful if you
want do a similar operation but just
with the slight variation in some
answers and indices this becomes very
this kind of looping statement becomes
very useful in while doing you know
while doing array operations and all and
we'll come to the array operations later
okay now I just run this again just to
give you guys a flavor
okay now let's give a really big term
like five like ten okay and then again I
give another multiple ten okay and I
give it like twelve terms look at the
results
it's just multiplying and go on on
increasing and after a particular point
after a particular point it loses
country it becomes too much and this
this valley should is not supposed to
happen but we're getting some kind of
answers here and similarly we're getting
another entirely different answer here
they are also getting a different answer
here different answer here so do you
think the problem crashed or something
well not exactly but what I felt is
there is there is some problem with the
numbers that is happening inside now
what exactly is this happening the
program is right programs are really
impeccably good but there is something
going on inside inside and all that's
still causing this answers to go do
different what is that mean I really
really can't ignore this in the extra
total guys okay now that's all I have
for you guys in this tutorial thank you
guys for watching see you guys next time
and in the next tutorial the answer for
this lies because of the kind statement
and that will explain you guys could
more clearly as to what's going on so
thank you guys for watching see you guys
next time bye