MIPS Tutorial 37 - 2D Arrays Video Lecture - MIPS Assembly Programming

hello everybody this is a male and
welcome back to another tutorial about
MIPS assembly language in this tutorial
I will explain one of my favorite topics
in mix assembly language and the topic
is multi-dimensional arrays and this
topic is very important because as you
probably know multi-dimensional arrays
are used a lot in high-level languages
like C C++ Java etc so as you know my
name is Emile Peralta and I hope you
enjoyed this video in the next video I'm
gonna teach you the implementation how
to actually write your own 2 dimensional
array in nips but before that you need
to actually know what I'm doing so I
want to explain the basic idea so my
goal here is to give you a summary of
the implementation of multi-dimensional
arrays in assembly language so the truth
of our memory in reality memory is a
single dimension entity so what that
means is that a multi-dimensional array
is implemented as a set I mean a set of
single dimension arrays and there are
two ways to implement multi-dimensional
arrays one way is row-major
representation and the other way is
column-major representation row-major
representation is the most widely used
collimator representation was widely
used in the old days for trend actually
at first was using column-major
representation so in a high-level
language like C or C++ you can observe
that this declaration right here int
array 3 4 is going to create an array a
two-dimensional array of integers that
has 3 rows and 4 columns
and you can observe all the elements
there so if you see this uh the first
element is here then you have the second
element the third etc now how can we do
that if we only have one dimension in
physical memory I mean how can we
represent a two-dimensional array with
only one dimension available to us well
if we use the row major representation
we have to place all the rows
sequentially one after the other so we
go row by row and we place those rows
next to each other one after the other
so we start here 0 1 2 3 then we go to
the next row four five six seven four
five six seven and then go to the next
row 8 9 10 11 and this is row major
representation and once we have all
these values placed in this manner we
can use the following mathematical
formula and this formula is going to
allow us to treat these representation
these values as two-dimensional array so
the address of an element that I want to
get is equal to the base address of the
array so let's say that if I want to get
this element 3 the address of this
element is the base address so remember
it makes the base address is the label
of the array plus the row index so the
row index of 3 is 0 this is the index of
the row times the number of columns the
column size how many columns we have 1 2
3 4 columns so in this case the number
of columns could be 4 plus the column
index and what is the column index 4 3
is 3 and then we have to multiply by the
size of the element the data size
because these are integers
the data size is four bytes so we
multiply by four so the address of
element three would be equal to the base
address of the array
the initial address of the array given
by the label plus the row index which is
zero times the number of columns which
is four plus the column index which is
three times the data size or in this
case which is four bytes because these
are integers if they were doubles it
would be eight bytes the only
representation that we have is column
major representation and this
representation is similar to row major
the main difference is that instead of
going row by row we go column by column
clicking each value next to each other
sequentially so we have sets of arrays
of single dimensional arrays so we go 0
1 2 here then we go to the next column 3
4 5 here and we go to the next column 6
7 8 here 6 7 8 and we go to next column
9 10 11 and we place these values this
way and this is column major
representation so if we use column major
representation we have to use the
following formula this formula is going
to allow us to get any element by simply
plugging the values so it's very similar
to the row major formula so if we want
to get for example this element 2 we say
the address of the element that I want
is equal to the base address that would
be given by the label in mix or the
initial address of the array plus the
column index the column index is 0 times
the number of rows how many rows we have
1 2 3 rows close the row index and the
row index is 2 times the data size and
remember that we are dealing with
integers so the data size is 4 and that
would give us the address of element 2
and we can simply access
that element it means assembly language
and these applies to any assembly
language but because this is about memes
I just I just I'm talking about me
specifically so thank you for watching
this tutorial now that you know the
basic idea
you should watch my next tutorial where
I program it to the array inmates
assembly language it's going to be an
awesome tutorial you're going to learn a
lot and you're going to become a better
mix programmer it may be a better
programmer not only amines but in any
language because you're going to know
how actually a two-dimensional array is
implemented in assembly language so
thank you for watching my tutorials and
really appreciate it please don't forget
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support me and thank you so much see you
next time