Some details about Multi dimensional arrays in C...

An array can be defined as the collection of variables of the same type that are referenced by a common name. Arrays are of two types namely one dimensional arrays and multi dimensional arrays. One dimensional array consists of finite homogenous elements whereas a multi dimensional array is composed of elements each of which is itself an array. Arrays refer to a named list of a finite number n of similar data elements. Each of the data elements can be referenced respectively by a set of consecutive numbers, usually 0, 1, 2, 3, 4,….., n. the simplest form of a multi dimensional array is the two dimensional array.

You can declare a two dimensional array as follows:
Type array name [ rows ] [ columns ];

Where type is the base data type of the array having name name, rows, the first index, refers to the number of rows in the array and columns, the second index refers to the number of columns in t5he array. For example:

Int sales [ 5 ] [ 10 ] ;

The general form of array initialization is shown below:

Type array name [ size N ] = { value list } ;

The value list is a comma separated list of array elements values. The element’s values in the value list must have the same data type as that of the base type of the array.
Int days [ 5 ] = { 1, 2, 3, 4, 5 } ;

Character arrays can also be initialized as shown below:
Char string [ 10 ] = { ‘c’ , ‘a’ , ‘t’ ‘\0’ } ;

Multi-dimensional arrays can also be initialized in the same way as simple dimensions one. For example:
Int abc [ 3 ] [ 2 ] = { 1, 1,
2, 2,
3, 3 } ;

This can be done it the other way also :
Int abc [ 3 ] [ 2 ] = { 1, 1, 2, 2, 3, 3 } ;

A multi dimensional array of strings can be initialized as shown below:

Type array name [ size N ] = { value list } ;

Here type declares the base type of the array, the array name specifies the name with which the array will be referenced and size defines how many elements the array will hold. The size must be an integer value or integer constant without any sign. The value list is a comma separated list of array’s elements values. The element values in the value list must have the same data type as that of the base type of the array.

Int days [ 5 ] = { 1, 2, 3, 4, 5 } ;

Character arrays can also be initialized as shown below:
Char string [ 10 ] = { ‘c’ , ‘a’ , ‘t’ , ‘s’ , ‘\0’ } ;

Multi dimensional arrays are also initialized in the same as the single dimensional one. For example:
Int cube [ 3 ] [ 2 ] = { 1, 1,
2, 2,
3, 3 } ;
This can be done in the other way also:
Int abc [ 3 ] [ 2 ] = { 1, 1, 2, 2, 3, 3 } ;

A multi dimensional array of strings can be initialized as shown below:
Char abc [ 3 ] [ 2 ] = { “Sunday” , “Monday” } ;

C allows you to skip the size of the array in an array initialization statement. This is called unsized array initialization. C allows arrays of more than 2 dimensions. The exact limit of dimensions is determined by the compiler we are using.

Some details about Strings and Arrays of Strings in C

Multiple character constants can be dealt with in 2 ways in C. if enclosed in single quotes, these are treated as character constants and if enclosed in double quotes, these are treated as string literals. A string literal is a sequence of characters surrounded by double quotes. Each string literal is automatically added with a terminating character ‘\0’. Thus, the string “abc” will actually be represented as follows:

“ abc \0” in the memory and its size is not 3 but 4 characters ( inclusive of terminator character ).

Arrays refer to a named list of a finite number n of similar data structure elements. Each of the data elements can be referenced respectively by a set of consecutive numbers, usually 0, 1, 2, 3, ……., n. if the name of an array of 10 elements is ARR, then its elements will be referred as shown below:

ARR [ 0 ], ARR [ 1 ], ARR [ 2 ], ARR [3], …… ARR [9]

Arrays can be one dimensional, two dimensional or multi dimensional. The functions gets() and puts () are string functions. The gets() function accepts a string of characters entered at the keyboard and places them in the string variable mentioned with it. for example :

Char name[ 21 ];

The above code declares a string namely name which can store 20 valid characters ( width 21 specifies one extra character ‘\0’ with which a string is always terminated ). The function gets() reads a string of maximum 20 characters and stores it in a memory address pointed to by name. As soon as the carriage return is pressed, a null terminator ‘\0’ is automatically placed at the end of the string. The function puts () writes a string on the screen and advances the cursor to the newline. Any subsequent output will appear on the next line of the current output by puts ().

Arrays are a way to group a number of items into a larger unit. Arrays can have data items of simple types like int or float, or even of user defined types like structures and objects. An array can be of strings also. Strings are multi dimensional arrays comprised of elements, each of which is itself an array.

A string is nothing but an array of characters only. In actual C does not have a string data type rather it implements string as single dimension character arrays. Character arrays are terminated by a null character ‘\0’. So, for this reason the character arrays or strings are declared one character larger than the largest string they can hold.

Individual strings of the string array can be accessed easily using the index. The end of a string is determined by checking for null character. The size of the first index ( rows ) determines the number of strings and the size of the second index ( columns ) determines maximum length of each string. By just specifying the first index, an individual string can be accessed. You can declare and handle an array of strings just like a two dimensional array. See an example below:

Char name [10] [20] ;

Here the first dimension declares how many strings will be there in the array and the second dimension declares what will be the maximum length of a string. Unlike C++, C has some different functions for adding or concatenating strings, checking string length and to see the similarity of two strings. The functions are namely strlen, strcmp, strcat, strrev etc and are included in header file string.h. Strings are used for holding long inputs.

Black Box Testing Technique - Orthogonal Array Testing (OATS)

Orthogonal array testing enables you to design test cases that provide maximum test coverage with reasonable number of test cases. This type of testing can be applied to problems which has relatively small input domain but too large to accommodate exhaustive testing. Orthogonal array testing is more suitable in finding errors associated with faulty logic within a software component.

Orthogonal arrays are two dimensional arrays of numbers which possess the interesting quality that by choosing any two columns in the array you receive an even distribution of all the pair-wise combinations of values in the array.

The benefits of orthogonal array testing includes:
- lower execution time.
- lower implementation time.
- code coverage is high.
- overall productivity increases.
- the analysis of results take less time.

Orthogonal array testing uses the following terminology:
- Runs are the number of rows in an array.
- Factors are the number of columns in an array.
- Levels are the maximum number of values that can be taken on by any single factor.

Orthogonal array testing (OAT) helps in optimizing testing by creating an optimized test suite, detects all kind of faults, guarantees the testing of pair wise combinations, less prone to errors, simpler to generate and is independent of platforms and domains.

What are four major elements of design model in software engineering ?

There are two dimensions in which a design model can be illustrated: process and abstraction dimension. Process dimension points the changes in the design model as the design tasks are implemented as part of software process. Abstraction dimension represents the level of detail as each element of analysis model is transformed into design equivalent and refined iteratively.

Design model elements are not developed in a sequential fashion. The design model has four major elements:
- Data
- Architecture
- Components
- Interface

Data design focuses on files or databases at an architectural level and on a component level, data design considers the data structures that are required to implement local data objects.

The architectural model is derived from the application domain, the analysis model and available styles and patterns.

The interface design elements for software tells us how the information flows in and out of the system and how it is communicated among the components. There are three parts to interface design elements: the user interface, interfaces to systems external to application and interfaces to components within the application.
User interface elements include aesthetic elements, ergonomic elements and technical elements. External interface design requires information about entity to which information is sent or received. Internal interface design is closely related to component level design.

The component level design elements describes the internal detail of software component. The component level design defines data structures for all local data objects and algorithmic detail processing that occurs within a component and an interface that allows access to all behaviors.