IGNOU BCA 1st sem Solved Assignment -What are the uses of Arrays in programming? Explain with the help of an example. Also explain how functions and subroutines are different to each other.

What are the uses of Arrays in programming? Explain with the help of an example. Also explain how functions and subroutines are different to each other.

Ans

Array in most programming langauges like C ,C++, Java etc is a static , homogeneous and lineardata structure.

A data structure itself is a mathematical and logical model to organise data.It clearly specifies the domain of the data that can be stored in the structure and the collection of valid operations (functions) that can be performed on that data. Array is a linear structure in the sense that the data is organised sequentially(one after another in a contineous chunck of memory).

It is a homogeneous data structure i.e. it contains elements which are of the same data type.Thedata type of array can be inbuilt like int , float ,char, double and even user defined that is created using a structure or a class.

The main use of an array is to oragnise homogeneous data together as a group to perform operations on data in a collective manner since traversal and retrieval becomes easy.Whenever a homogeneous list(One Dimendional or Multi-Dimensional)has to be implemented we make use of array.The advantage of array lies in the fact that it uses indexed represenattion enabling us to access any member element directly.

The example of practical use of array in progarmming will be creation of index lists,

pointer arrays,matrix operations(transpose,addition ,subtraction,multiplication,inverse etc.).

Subroutines and Functions

When a program is more than a few hundred lines long, it gets hard to follow. Fortran codes that solve real engineering problems often have tens of thousands of lines. The only way to handle such big codes is to use a modular approach and split the program into many separate smaller units called subprograms.

A subprogram is a (small) piece of code that solves a well-defined sub-problem. In a large program, one often has to solve the same sub-problems with many different data. Instead of replicating code, these tasks should be solved by subprograms. The same subprogram can be invoked many times with different input data.

Fortran has two different types of subprograms, called functions and subroutines.

Functions

Fortran functions are quite similar to mathematical functions: They both take a set of input arguments (parameters) and return a value of some type. In the preceding discussion we talked about user defined subprograms. Fortran also has some built-in functions.

A simple example illustrates how to use a function:

X = cos(45.24)

Here cos is the cosine function. There are many built-in functions in Fortran. Some of the most common are:

abs absolute value

sqrt square root

sin sine

cos cosine

atan arctangent

exp exponential (natural)

log logarithm (natural)

In general, a function always has a type. Most of the built-in functions mentioned above, however, are generic. So in the example above, pi and x could be either of type real or double precision. The compiler would check the types and use the correct version of cos (real or double precision). Unfortunately, Fortran is not really a polymorph language so in general you have to be careful to match the types of your variables and your functions!

Main differences between FUNCTIONS and SUBROTINES

A SUBROUTINE has no value associated with its name. All outputs are defined in terms of arguments; there may be any number of outputs.

A SUBROUTINE is not called into action simply by writing its name, since no value is associated with the name. Instead, we write a CALL statement to bring it into operation; this specifies the arguments and results in storing all the output values.

Since the output of a SUBROUTINE may b any combination of the various types of values, there is no type associated with the name and likewise no convention attached to the first letter of the name.