March 2020

Software Development Process
• Software development process is carried out in various steps. These steps an basically called as software development phases.
• The system gets developed gradually during each of these phases. For example -after requirement analysis phase, the requirements of the system can be identified and SRS is prepared. After the software design phase, the design of the system on paper gets ready and so on.

Software Development Process & Environment 
• The collection of these phases determine the life cycle of software. These phases are used in various process models such as waterfall model, life cycle model and so on.
• Thus we can define the software development process as

Definition : Software development process is a sequential combination of phases, each having well defined starting and ending points and at each phase there are identifiable deliverables to the next phase.
• During the software development process, the deficiencies of previous stage must be identified and corrected.
• Various phases of software development process are
-Requirement analysis & specification
-Software design and specification
-Implementation
-Verification and validation
-Testing
-Maintenance

Phases of software development process

(1) Requirements Analysis and Specification

The requirements of the system are identified and documented in this phase.
• The requirement gathering and identification tasks are jointly carried out by the users and developers of the system.
. These requirements are then documented in a document which is popularly known as Software Requirement Specification(SRS),
• The SRS does not specify how to meet these requirements in the system.

(2) Software Design and Specification

• The SRS is used during the software design and specification. During this phase,varlous software modules and their interfaces are designed.
• In this phase, the software design document is prepared. This document specifies the functionality of each module, their interfaces and the software architecture used.

(3) Implementation

• Implementation is a phase in which the coding is done in suitable programming language with the help of design document.
• Ideally it should be simply mapping of software design into the corresponding code.
• At the end of this phase, fully implemented and documented system is ready for testing and validation

(4) Verification and Validation

•This phase is for checking the quality of the software system being developed.
•Verification means -" Are we building the product right?" and validation means -
" Are we building the right product?".

(5) Testing

•Testing is a process of finding bugs or errors from the system.
•Testing is done mainly for two things-
i) Module testing 
ii) Integration testing
•Module testing is performed to know whether particular module is working according to its specification or not. While integration testing is to uncover the inter-modular inconsistencies.

(6) Maintenance

• After delivering the software system to the user, there are chances for changes in the system due to some malfunctioning or due to some additional functionality.
•Many times the changes are made in the system to withstand in a new operational envirornment.
•This cost of maintenance is always higher than all other the software development.

Language and Software Development Environment

Definition of Software Development Environment : The software development environment means an integrated set of tools and techniques that are used development of software.
• This environment (actually set of tools) are used in al phases of software development such as-requirements, design, coding testing and so on.
• The ideal scenario for use of environment can be specified as follows -

Step 1: During requirement analysis and specification phase, the environment keeps track of requirements. It helps in identifying incompleteness and inconsistency in requirements. It also provides the facility to validate the requirements.

Step 2: After completion of requirements analysis, the software designers interact with the environment and get the help in creating initial system design. This design is then refined to get final design for the system.

Step 3 : At the implementation (ie. coding) phase, the environment assists the software developer by automating some development steps, by suggesting the reuse of existing design and reuse of components from library. Various tools that are commonly used in this phase are - interactive editors, compilers, interpreters
linker, debuggers and so on.

Step 4: The impletation is further tested in order to find bug. There are various automated testing tools available which help in generating the test cases.

• The software development cenvironment can be commercially provided by the support tools called CASE i.e. Computer Aided Software Engineering.

 ROOTED TREES

Many of the applications of graph theory, particularly in computer science, use a certain kind of tree, called a rooted tree. These trees are used as models for the structures of file
directories. Some of the other important uses of rooted trees include the representation and
sorting of data, the representation of algebraic expressions etc.
A tree in which one vertex (called the root) is distinguished from all the other vertices is known as rooted tree.
Trees without any root are called free trees or simply trees. A
vertex of degree one which is not a root is called a leaf or external node and all the vertices
including the roots) that are not leaves are called interior nodes. For instance in Fig.7.1 below a vertex v is a root for all the trees shown.
Fig 7.1

The other example of rooted tree is sorting of mail according to the zip code. 
Consider the Fig. 7.1The point N from where all the mail goes out is distinguished from the rest of the vertices. Hence N can be considered as the root of the tree.
A rooted tree is often used to specify hierarchical relationships. 
A example of such a tree, which is an organization chart of a corporation is given in the following Fig

Directed Tree
A directed tree (a tree with directions) is called a rooted tree if there is exactly one vertex
whose incoming degree is zero and ail other vertices have incoming degree one The vertex
with incoming degree 0 is known as the root of the tree In Fig 7.15 the vertex a is the root
of the directed tree.
Fig 7.15


Fig. 7 15
In a directed rooted tree, a vertex whose outgoing degree is 0 is called a leaf and a vertex
whose outgoing degree is non zero is called a branch node or an internal node In Fig. 7.15
the vertices b, c and f are branch nodes and the vortices d, e, g are leaves.
Now we are in position to defne the level of a vertex in a rooted tree.
A vertex x ina rooted tree is said to be at level n if there
is a path of length n from the root to the vertex x. The
height of the tree is the maximum of the levels-of-its
vertices. Height of the tree is also called the depth of the
tree. In the following Fig. 7.16, b is at level 1 and g is at
level 3 The height of the tree IS 3.
fig.7.16

In a rooted tree, if the level of a vertex y in greater than the level of the vertex x, then we say
y is below x. If y is below x and there is an edge from x to y, then we say y is on of x.
Also, x is said to be the father of y. Two vertices are said to be brothers if they are sons of
the same vertex If P = (X, V V2 - Vn- y) is a path from « to y, then y is called a
descendant of x. Also, x is said to be an ancestor of y. These terms clearly indicate that
family trees are indeed rooted trees. To understand these terms, consider rooted tree G, in e verter c Hence e is the son of cor cis the father of e. Also
Fig. 716. The vertex e is below
e and f are the sons of c. Therefore the vertices e and fare brothers. Also, the vertices c and g are connected by the sequence of edges and is below c Therefore, g is a descendant of c or we can say cis an ancestor of g.

The degree of a tree is the maximum degree of the nodes in the tree In Fig 7.16, the degree of the tree is 3

A forest is a set of disjoint trees If we remove the root of a tree, we get a forest i.e. set of disjoint trees.

In another words, if the root and corresponding cdges connecting the nodes (sons) to the root are deleted from a tree, we obtain a set of disjoint trees. This set of disjoint trees is
called a forest
"We present now the definitions of subtree and m ary tree in a rotated tree" in a rooted tree T, a vertex x, together with all its descendants, is calied the subtree of T
rooted at x. 
Following Fig 7.17 shows the rooted tree T, and its subtree T' rooted at b.
Fig 7.17

A rooted tree in which every interior node las atmost m sons is called an m-ary tree.

An m-ary tree is said to be regular m-ary tree or full m-ary tree if every branch node has exactly m sons. For example, in the following Fig. 718 G, is a 2 - ary tree or binary tree but it is not a regular binary tree. G, is a regular 3 - ary tree or a ternary tree.
Fig 7.18
In a regular m-ary tree, the relation between the interior nodes and the total number of nodes is given by following theorem.

Theorem
A regular m-ary tree with i interior nodes has (mi + 1) nodes at all.
Proof:
Suppose the given regular m-ary tree has n number of vertices, out of which there are i interior vertices.

Clearly, the number of leaves or sons in the tree is t = (n-i).
Since the given graph is a regular m-ary tree hence each of the i interior nodes has m sons
and thus the regular m-ary tree will have total (mi) sons.
But root is not a son.
Therefore the given tree has a total of (mi + 1) number of vertice(s).
Hence n = mi + 1 

Evolution of Computers-Brief History

History of computers Gives us the basic information about the technological development trends in computer in the past and its projections in the future.

The Secret History Of Evolution Of (a Brief History) Computer - Computer Architecture

The ancestors of modern age computers were the mechanical
and electromechanical devices. This ancestry can be traced as back as 17th century. when the first machine capable of performing four
mathematical operations, viz., addition, subtraction, division and
multiplication.

Mechanical Computers

Blaise Pascal made the very first attempt towards the automatic computing. He invented a device, which consisted of lots of gears and chains and used to perform repeated additions and subtractions.
This device was called Pascaline. Later many attempts were
made in this direction; we will discuss some details about the
innovation by Charles Babbage, the grandfather of modern
computer. 
He designed two computers.

* The difference engine

It was based on the mathematical principle of finite differences and was used to solve calculations on large number using a formula. It was also used for solving the polynomial and
trigonometric functions.

* The analytical engine by Babbage

It was a general purpose computing device, which could be used for perferming any mathematic operation automatically. It consisted of the following components:
The store : A mechanical memory unit consisting of sets of counter wheels.
The mill : An arithmetic unit, which is capable of performing the four basic arithmetic operations.

Cards: 

There are basically two types of cards:

Types of Cards-
1.Operation Cards
2. Variable Cards

(i) Operation cards
Selects one of the four arithmetic operations by activating the
mill to perform the selected operation.

(ii) Variable cards
Selects the memory location to be used by the, mill for a particular operation (i.c. the source of the operands and the destination of the results).
Output : Could be directed to a printer or a card punch device.

The basic feature of this analytical engine were:
-It was a general purpose programmable machine.
-It had the provision of automatic sequence control, thus enabling programs to alter its sequence of operations.
-The provision of sign checking of result existed.
-Mechanism for advancing or reversing of control card was
permitted thus enabling execution of any desired instruction.
-In other words, Babbage has devised a conditional and
branching instructions.
-The Babbage machine is fundamentally the same as a
moden computer.

The First Generation : Vacuum Tubes
The first electronic computer was constructed using vacuum tubes. The first computer constructed using vacuum tube technology vas ENIAC (Electronic Numerical Integrator and Calculator).
-It was enormous machine weighing about 30 tons.
-It contained more than 18,000 vacuum tubes.
-It consumed 140 kilowatts of power.
-It was a decimal rather than a binary machine.
-It was capable of 5000 additions per second.
-It had memory to hold twenty 10 digit decimal numbers.
-It stored programs and data in separate memories.

EDVAC (Electronic Device Variable Computer)
ENIAC stored program and data in separate memories entering or altering program was a difficult task, EDVAC stores both program and data in the same memory.

Concept of common memory for both program and data
-EDVAC has two kinds of memory : a fast main memory with
a capacity of 1024 and slower secondary memory of 20k words.
-It stored and processed number in binary form to minimize
hardware cost. It processed data bit by bit.
-Prior to execution, a set of instructions forming a program is
placed in the EDVAC main memory. The instructions were then transferred one a time from the main memory to the CPU for execution.
-Each instruction had a well defined structure of the form:
A1,A2,A3,A4,op.
-The meaning :perform the operation op (addition, subtraction, multiplication, etc.) on the contents of main memory locations A1, and A2, and then place the result In main memory location A3,A4 specifies the address of the next instruction to be executed.

The trends, which were encountered during the era of first-generation computers.

-Centralized control in a single CPU; all the operations required a direct intervention of the CPU.
-Use of ferrite-core main memory had started.
-Concept of virtual memory had started.
-Punched cards were used as input.
-Magnetic tapes and magnetic drums were used as secondary
memory.
-Binary code or machine language was used for programming.
-Towards the end due to diffīculties encountered in use of machine language as programming language, the use of symbolic language that is now called assembly language started.
-Assembler, a program that translates assembly language programs to machine language was made.
-Computer was accessible to only one programmer (single user mode).
-Advent of Von Neumann architecture.

The Second Generation: Transistors

-The use of the transistors defines the second generation of
computers.
-Vacuum tubes were replaced by transistors. The transistor is smaller, cheaper and dissipates less heat than a vacuum tube.
-The second-generation characterizes greater speed, larger memory capacity and a smaller size over the first generation.
-Computer hardware and software evolved rapidly after the introduction of the second-generation computers.
-Complex instructions were added to the set of instructions.
-More registers were added to the CPU to facilitate data and
address manipulation.
-Floating point number was introduced to support scientific 
application.
-Input/output operations were added for easy transfer of the
information to and from peripheral devices like printer and
secondary memory
-High level programming languages were introduced.
-Provision of system software with the computer


The Third Generation :Integrated Circuits

This generation is associated with the introduction of Integrated Circuits (ICs) This replaced the discrete electronic circuits used in second generation camputers

ICs allowed a large number of transistors and associated
components to be combined on a tiny piece of silicon wafer.

IC technology initiated a long terms trend towards
(1) Higher speed
(2) Smaller size
(3) Lower hardware cost
(4) Lower power consumption
(5) More reliable circuit

IBM developed the most influential third generation computer, the system/360. The machine becamec a standard for all main frame computers.
-It was based on Von Neumann architecture.
-It had about 200 distinct instruction types
-It had many addressing modes.
-It supported various data types.
-It supported both fixed point and floating point numbers.
-It had 16 general purpose registers.
-The CPU had two major control states
(1) Supervisory state for use by the operating system.
(2) User state for executing application programs.

 Later Generations : VLSI 

VLSI allowed manufactures to fabricate a CPU, main
memory or even all the electronic circuit of a computer on a single
IC that can be mass produced at a very low cost. This resulted in a
new class of machines ranging from portable personal computers to
supercomputers that contain thousands of CPUS. Two most
important impact of VLSI are:
(1) Semiconductor memory
(2) Microprocessors

Programmable Logic Devices (PLDs) Lesson Objectives: In this lesson you will be introduced to some types of Programmable Logic Devices (PLDs): ¾ PROM, PAL, PLA, CPLDs, FPGAs, etc. ¾ How to implement digital circuits using PLAs and PALs. 

Introduction: An IC that contains large numbers of gates, flip-flops, etc. that can be configured by the user to perform different functions is called a Programmable Logic Device (PLD). The internal logic gates and/or connections of PLDs can be changed/configured by a programming process. One of the simplest programming technologies is to use fuses. In the original state of the device, all the fuses are intact. Programming the device involves blowing those fuses along the paths that must be removed in order to obtain the particular configuration of the desired logic function. PLDs are typically built with an array of AND gates (AND-array) and an array of OR gates (OR-array).

Advantages of PLDs: Problems of using standard ICs: Problems of using standard ICs in logic design are that they require hundreds or thousands of these ICs, considerable amount of circuit board space, a great deal of time and cost in inserting, soldering, and testing. Also require keeping a significant inventory of ICs. Advantages of using PLDs: Advantages of using PLDs are less board space, faster, lower power requirements (i.e., smaller power supplies), less costly assembly processes, higher reliability (fewer ICs and circuit connections means easier troubleshooting), and availability of design software. There are three fundamental types of standard PLDs: PROM, PAL, and PLA. A fourth type of PLD, which is discussed later, is the Complex Programmable Logic Device (CPLD), e.g., Field Programmable Gate Array (FPGA). A typical PLD may have hundreds to millions of gates. In order to show the internal logic diagram for such technologies in a concise form, it is necessary to have special symbols for array logic. Figure shows the conventional and array logic symbols for a multiple input AND and a multiple input OR gate.

Three Fundamental Types of PLDs: The three fundamental types of PLDs differ in the placement of programmable connections in the AND-OR arrays. Figure shows the locations of the programmable connections for the three types.

¾ The PROM (Programmable Read Only Memory) has a fixed AND array (constructed as a decoder) and programmable connections for the output OR gates array. The PROM implements Boolean functions in sum-of-minterms form. ¾ The PAL (Programmable Array Logic) device has a programmable AND array and fixed connections for the OR array. ¾ The PLA (Programmable Logic Array) has programmable connections for both AND and OR arrays. So it is the most flexible type of PLD. 

The ROM (Read Only Memory) or PROM (Programmable Read Only Memory): The input lines to the AND array are hard-wired and the output lines to the OR array are programmable. Each AND gate generates one of the possible AND products (i.e., minterms). In the previous lesson, you have learnt how to implement a digital circuit using ROM. 

The PLA (Programmable Logic Array): In PLAs, instead of using a decoder as in PROMs, a number (k) of AND gates is used where k < 2n , (n is the number of inputs). Each of the AND gates can be programmed to generate a product term of the input variables and does not generate all the minterms as in the ROM. The AND and OR gates inside the PLA are initially fabricated with the links (fuses) among them. 

Programmable Logic Device 

The specific Boolean functions are implemented in sum of products form by opening appropriate links and leaving the desired connections. A block diagram of the PLA is shown in the figure. It consists of n inputs, m outputs, and k product terms.  

The product terms constitute a group of k AND gates each of 2n inputs. Links are inserted between all n inputs and their complement values to each of the AND gates. Links are also provided between the outputs of the AND gates and the inputs of the OR gates. Since PLA has m-outputs, the number of OR gates is m. 

The output of each OR gate goes to an XOR gate, where the other input has two sets of links, one connected to logic 0 and other to logic 1. It allows the output function to be generated either in the true form or in the complement form. The output is inverted when the XOR input is connected to 1 (since X ⊕ 1 = X/ ). The output does not change when the XOR input is connected to 0 (since X ⊕ 0 = X). Thus, the total number of programmable links is 2n x k + k x m + 2m. The size of the PLA is specified by the number of inputs (n), the number of product terms (k), and the number of outputs (m), (the number of sum terms is equal to the number of outputs). 

Field Programmable Gate Arrays (FPGAs): 
The FPGA consists of 3 main structures: 
1. Programmable logic structure, 
2. Programmable routing structure, and 
3. Programmable Input/Output (I/O). 

1. Programmable logic structure The programmable logic structure FPGA consists of a 2-dimensional array of configurable logic blocks (CLBs). Each CLB can be configured (programmed) to implement any Boolean function of its input variables. Typically CLBs have between 4-6 input variables. Functions of larger number of variables are implemented using more than one CLB. In addition, each CLB typically contains 1 or 2 FFs to allow implementation of sequential logic. Large designs are partitioned and mapped to a number of CLBs with each CLB configured (programmed) to perform a particular function. These CLBs are then connected together to fully implement the target design. Connecting the CLBs is done using the FPGA programmable routing structure. 

2. Programmable routing structure To allow for flexible interconnection of CLBs, FPGAs have 3 programmable routing resources: 1. Vertical and horizontal routing channels which consist of different length wires that can be connected together if needed. These channel run vertically and horizontally between columns and rows of CLBs as shown in the Figure. 2. Connection boxes, which are a set of programmable links that can connect input and output pins of the CLBs to wires of the vertical or the horizontal routing channels. 3. Switch boxes, located at the intersection of the vertical and horizontal channels. These are a set of programmable links that can connect wire segments in the horizontal and vertical channels.

3. Programmable I/O These are mainly buffers that can be configured either as input buffers, output buffers or input/output buffers. They allow the pins of the FPGA chip to function either as input pins, output pins or input/output pins. 

Random Access Memory

A memory unit is a collection of storage cells together with associated circuits needed to transfer information in and out of the device. 
Memory cells can be accessed for information transfer to or from any desired random location and hence the name randomaccess memory, abbreviated RAM. 
A memory unit stores binary information in groups of bits calledwords. 1 byte = 8 bits 1 word = 2 bytes. 
The communication between a memory and its environment is achieved data input and output lines, through address selection lines, and control lines that specify the direction of transfer. 

Content of amemory 
 Each word in memory is an identification called assigned number, starting from 0 an address, up to 2 k -1, where k is the number of addresslines. 
 The number of words in a memory with one of the letters K=210, M=220, or G=230. 64K = 2 16 2M = 2 21 4G = 2 32

READ ONLY MEMORY (ROM) 

• Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer.Unlike RAM, ROM cannot be written to. 
• Because data stored in ROM cannot be modified (at least not very quickly or easily), it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to require frequent updates). 
• It is non-volatile which means once you turn off the computerthe information is stillthere. 

Title: String Operations

Objectives: 

 To implement different operations on strings like Creating, copying, modifying, concatenating, reversing, Finding substrings, etc.  To simulate the inbuilt string operations function.

String: 
A string is a character array terminated by a null character (\0). In C, the null character can be used to mark the end of a string. A string constant is a series of characters enclosed by double-quotes. The C compiler automatically appends a null character to the array that has been initialized by a string constant. char str[7] = "Hello!";

Substring : 
A string is a substring of the main string if it is a part of the main string. 

Palindrome: 
A string is a palindrome if the reverse of the string is equal to the original string. e.g: nitin 

Different string operations are as follows : 

1) int strlen( const char *str) -- Calculates string length excluding last null character. 

2) char * strcpy( char *dest, const char * src) – Copies string from source to destination 

3) char *strcat(char *dest, const char * src ) – Appends source string at the end of destination and returns pointer to the destination.

4) int strcmp(const char *str1, const char * str2) – Does an unsigned comparison of two strings character by character and returns difference as an integer. If diff = 0 strings are equal If diff < 0 string1 is smaller than string2 If diff > 0 string1 is greater than string2

5) char * strrev( char *str) – Reverses the input string and returns a pointer to the reversed string. 

6) char *strstr( char *str1, char *str2) – Checks for string2 in string1 and returns pointer to location of first occurrence. 

7) String palindrome – Checking if reversed string is same as original string. The strlen() Function 

Strlen() Function-

The strlen() function can be used to measure the length of a string. This function does not count the null character in the last element The syntax for the strlen() function is size_t strlen(const char *s); Here s is a char pointer variable. The return value from the function is the number of bytes. size_t is a data type defined in the string.h header file. The size of the data type depends on the particular computer system. 

String Operations Data Structures in C++


Strcpy() Function-

The strcpy() Function If you want to copy a string from one array to another, you can copy each item of the first array to the corresponding element in the second array, or you can simply call the C function strcpy() to do the job for you. The syntax for the strcpy() function is char *strcpy(char *dest, const char *src); Here the content of the string src is copied to the array referenced by dest. The strcpy() function returns the value of src if it is successful. The header file string.h must be included in your program before the strcpy() function is called. 

Strcat() Function-

The strcat() Function strcat appends a copy of src to the end of dest. The length of the resulting string is strlen(dest) + strlen(src). The syntax for the strcat() function is char *strcat(char *dest, const char *src); strcat returns a pointer to the concatenated strings. 

Strrev() Function-

The strrev() Function Reverses all characters in a string (except for the terminating null) The syntax for the strrev() function is char *strrev(char *s); For example, it would change string\0 to gnirts\0 strrev returns a pointer to the reversed string. 

Strcmp() Function-

The strcmp() Function Compares two strings. The string comparison starts with the first character in each string and continues with subsequent characters until the corresponding characters differ or until the end of the strings is reached. The syntax for the strcmp() function is int strcmp(const char *s1, const char*s2); This function returns an int value that is < 0 if s1 < s2 == 0 if s1 == s2 > 0 if s1 > s2 

Strlwr() Function-

The strlwr() Function Converts uppercase letters (A to Z) in string s to lowercase (a to z). The syntax for the strlwr() function is char *strlwr(char *s); No other characters are changed. Return Value is a pointer to the string s. 

Strupr() Function-

The strupr() Function Converts lowercase letters (a to z) in string s to uppercase (A to Z). The syntax for the strupr() function is char *strupr(char *s); No other characters are changed. Return Value is a pointer to the string s. 

Strstr() Function-

The Strstr() Function Finds the first occurrence of a substring in another string The syntax for the strupr() function is char *strstr(const char *s1, const char *s2); strstr scans s1 for the first occurrence of the substring s2. Return Value: On success, strstr returns a pointer to the element in s1 where s2 begins (points to s2 in s1). On error (if s2 does not occur in s1), strstr returns null.

Top 10 Expected Questions Based On String Operations Data Structures Practical Approach: 

Q1. What is a string? How do you know its length? 

Q2. What are the main differences between a string constant and a character constant? 

Q3. Does the gets() function save the newline character from the standard input stream? 

Q4. What types of data can the scanf() function read? 

Q5. What are the left and right values (lvalue & rvalue)? 

Q6. How can you obtain the address of a variable? 

Q7. What is the concept of indirection in terms of using pointers? 

Q8. Can a null pointer point to valid data? 

Q9. What is the main difference between using scanf & gets for accepting strings ? 

Q10. How do you reference an array by using a pointer? 


Design Experiments: 


1. Simulate the following string library functions with pointers to arrays. 

char *strncpy(s,ct,n) Copies at most n characters of string ct to s Returns s. Pads with '\0's if t has fewer than n characters. 

char *strncat(s,ct,n) Concatenates at most n characters of string ct to end of string s; terminates s with '\0'. Returns s. 

int *strncmp(cs,ct,n) Compares at most n characters of string cs to string ct. Returns < 0 if cs < ct 0 if cs= =ct or > 0 if cs > ct 

char *strchr(cs,c) Returns a pointer to the first occurrence of c in cs or NULL if not present. 

char *strrchr(cs,c) Returns a pointer to the last occurrence of c in cs or NULL if not present

2. Simulate the following string library functions with pointers to arrays

size_t strspn(cs,ct) Returns length of prefix of cs consisting of characters in ct.

size_t strcspn(cs,ct) Returns length of prefix of cs consisting of characters not in ct. 

char *strpbrk(cs,ct) Returns pointer to first occurrence in string cs of any character of string ct, or NULL if none present.

char *strstr(cs,ct) Returns pointer to first occurrence of string ct in cs, or NULL if not present. size_t strlen(cs) Returns the length of string cs.  

char *strerror(n) Returns pointer to implementation-defined string corresponding to error n. 

char *strtok(s,ct) strtok searches s for tokens delimited by characters from ct, NULL if none are found. 

Implement above  by dynamically allocating memory for string and perform the various operations on strings with pointers to arrays.

Thus the String Handling Functions (StringCopy, StringLength, StringCompare, StringReverse, StringConcat, SubString) have been Successfully Learned.

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Object-Oriented Programming

PROGRAMMING TECHNIQUES

•   Unstructured programming

•   Procedural programming

•   Modular programming

•   Object-oriented programming

•   Generic programming         

    UNSTRUCTURED PROGRAMMING

•   Only one Program i.e. main Program

•   All the sequences of commands or statements in one programs called the main Program

•   E.g. Fortran, assembly language, old Basic

   MODULAR PROGRAMMING

•   Procedures with some common functionality are grouped together into separate modules
•   Program is categorized into several smaller modules
•   Each module can have its own data

   Procedural Oriented Language

• Conventional programming, using a high-level language such as COBOL, FORTRAN, and C are commonly-known as Procedure oriented language (POP).
• In POP numbers of functions are written to accomplish the tasks

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