C++ Introduction

Contents 1. C++ Language

1.1 Introduction 1.2 Basics of a C++ program 1.3 Variables 1.4 Constants 1.5 Data types 1.6 Operators 1.7 Expressions 1.8 Structure of a C++ program 1.9 Turbo C++ screen layout Exercise

2. Statements

2.1 Input and output statements 2.2 Control statements 2.3 If…Else statement 2.4 Switch case statement 2.5 Programs Exercise

3. Control statements 3.1 While statement 3.2 Do..while statement 3.3 For statement 3.4 Rules of FOR loop 3.5 Programs Exercise 4. Functions

4.1 Library functions 4.2 String functions 4.3 Programs Exercise

Introduction to C++ for class XI by P.N 2

1. C++ Language 1.1 Introduction to C++ language C++ was developed by Bjarne Stroustrup in the year 1979. It C++ combines the features of low level and high level programming languages. It is the extension of C Language and it was originally called as C with Classes and then it was renamed as C++. It is the most popular programming language widely used all over the world on different platforms and operating systems. It is mainly used for designing system software like compiler, interpreter, utilities, client applications, device drivers and video games etc. As the C++ is an extension of C, it is more compatible with C and it runs any type of C program smoothly. Advantages of C++ language a. It is a low level and system implementation language b. It has a relatively clear and mature standard c. C++ command are much familiar and user friendly d. C++ programs are very fast and efficient compared to other high level language programs e. A program written in C++ language can be run on any computer without any modification.

This is called portability of the programs f. The object oriented programming language feature helps to create and simulate real time

entities in the programming model. g. C++ provides rich set of library functions for variety of purpose; it also allows adding our

own functions as library functions. Disadvantages

a. It is not a pure object oriented language b. Does not provide strong data type checking c. Difficult to develop graphic applications like GUI d. Does not support dynamic memory allocation like pointers in C++

Steps in Learning C++ Language Like any communication language, you should learn all the basic concepts of C++ language thoroughly. The instructions of C++ language describe the usage of keywords with constants or variables. A program represents the set of instructions to solve a particular problem. A bug is called an error in the program and debugs stands for correcting the errors of the program. The term software stands for set of programs and documentation about a problem. Let us demonstrate the steps in learning C++ language as flowchart. Prepare your mind to Learn C++ language

Read Character set of C++ Language

Read variables, Constants and keywords


Practice syntax of Statements and functions

Create program For the problem

Run the program

Yes Modify the program Is there any Bug? No

Observe the output Of the program Figure 3.1 1.2 Basics of C++ Language Character set of C++ Language A character is the basic unit of any language that represents words, numbers or expressions. The following table summarizes the character set of C++ language.

Category Symbols Alphabets/Letters A to Z

a to z Digits 0 to 9 Special symbols ‘ “ , . : ; ? ! / \ | ~ _ $ % # & ^ * - +

< > ( ) [ ] { } = White spaces Blank space, Horizontal tab, carriage return,

new line and form feed Table 3.1 Keywords Keywords are the basic reserved words of C++ language that cannot be changed or used for other purposes. Statements are written using these keywords. There are 32 keywords available in standard C++ language. All the keywords must be written in small letters. Some of the commonly used keywords are as follows

Auto Default Goto Signed Break Do If Switch Case Double Int Unsigned Char Else Long Void Const Float Return While Continue For Short Main

Table 3.2


1.3 Identifiers or Variables It refers to the user defined names consisting of letters and digits, mainly serves for identifying the variables, functions, arrays, structures etc. The formal definition of a variable is that it is a quantity whose value can be changed during the execution of the program. Identifier identifies the data stored in memory locations by a unique address. Rules for defining a variable is as follows a. A variable can contain alphabets, digits and underscore b. A variable name can be up to 8 characters long. In case of more than 8 characters, the

remaining characters are ignored. Some versions of C++ accepts upto 40 characters. c. The first character of the variable must be an alphabet d. The character underscore is used to link between two words of long identifiers e. You can use either upper case or lower case, but the lower case letters are commonly used f. It is advised to give meaningful names for the variables so that they can be easily identified in

the lengthy program. Types of Variables C++ language provides rich set of data types for declaring variables. The type of the variable depends upon the data what we are assigning to the variable. But all those variables should be declared at the beginning itself. Some of the basic types of variables are given below

Variable type Declaration format Example values Integer int a,b; a=20;b=40; Real float x,y; x=20.56; y=0.8876; Character char choice choice = ‘y’; String char name[20]; name[]=”adhavan”

Table 3.3 Note: You can declare specific type of integer or the lengthy format of real numbers using the suitable keywords given in the later sections. Example The following table contains variables and also states whether it is valid or invalid with reason.

Variable Valid/Invalid Reason gross_sal Valid Underscore is allowed pay1 Valid Number is allowed $name Invalid First character must be alphabet net salary Invalid Blank space is not allowed return Invalid Keyword cannot be used sum,average Invalid Comma is not allowed 1person Invalid First character is given as digit name-age Invalid - is not allowed TOTAL Valid Capital letters are allowed as identifiers identifier_1 Valid But accepts only the first 8 characters si_ci_int Valid Underscores are allowed

Table 3.4


1.4 CONSTANTS A constant in C++ language is a quantity whose value cannot be changed during the execution of the program. The different types of constants in C++ language are as follows CONSTANTS Numeric Character Structured Integer Real Single String Array Pointer structure union Decimal Octal Hexa Figure 3.2 Let us see each of the above mentioned constants in detail. Numeric constants Digits and decimal point form a numeric constant. This can be used for arithmetic calculations. There are two types of numeric constants such as integer and real. Integer constant A number without decimal point is called integer constant. Example: 2922, -4354, 0, 20331, 10001 An integer number can also be given in the following three formats. Decimal It consists of digits 0 through 9, preceded by an optional + or – sign. Example: -8421, 0, 4123, +9993 Octal It consists of digits 0 through 7 with leading 0. Example: 0456, 0, 05731 Hexadecimal It consists of digits 0 through 9 and A through F. These digits are preceded by 0X or 0x. Example: 0xbc8, 0X0, 0X148A, 0x1243 The decimal type of integer constant is mostly used in our programs. You can also restrict the usage of integer constants to small or big using its sub types. These are explained in data types topic. Real or Float A number with decimal point is called floating-point number. A real number can be given in three different ways namely float, double and e-notation.


Float It uses four bytes for its storage and it can take values ranging from ___ to ____. Example: 23.4442, 0.99847, -0.33234 +123.3423 Double It uses eight bytes for storage and it can be used to represent big or small numbers. Example: 1010132.232323, -0.000044500033, -1010010233.3333 Rules for numeric constant a. A numeric constant must have at least one digit b. Integer constants should be written without decimal point and real numbers must have

decimal point c. A number can be written as either positive or negative using + or – sign. The default sign is

positive. d. Comma’s or blank spaces are not allowed in constants e. Special characters are also not allowed. E-Notation It is a special kind of real number that helps to process very big or very small numbers. The general format of e-notation is as follows

Mantissa e Exponent Where mantissa part consists of integer part, real part and sign of the number, Exponent part specifies the power value and the sign of the power. The absence of the sign indicates the power is positive. The letter e stands for base 10. Example: 1.23e23, -0.343e-10, +12345.343e+23 Rules for writing exponent component 1. The range of real constants expressed in exponential form is –3.4e38 to 3.4e38. It changes to

the double format. 2. Mantissa may have a positive or negative sign. Default is positive sign. 3. Exponent part must have at least one digit. 4. The letter e is used to separate mantissa and exponent. It represents base 10. Character constant It is classified into single character and string. They are as follows a. Single character An alphabet, digit or symbol enclosed in a single quote is called character constant. It denotes the ASCII value of the character and it can be used in calculations also. Example: ‘A’ ‘0’ ‘+’ ‘?’ ‘a’ The ASCII value of the character ‘A’ is 65, ‘B’ is 66…. ‘Z’ is 90, similarly the value of ‘a’ is 97, ‘b’ is 98…….’z’ is 122. The value of digit ‘0’ is 48, ‘1’ is 49….’9’ is 57. String constant Set of characters enclosed within double quotes is termed as string constants. A blank space (ASCII value is 32) is also called a character. Example: “ATOMIC ENERGY SCHOOL”, “kalpakkam”, “Narasimman”


Rules for writing character constants a. A character constant is either a single alphabet, digit or special character enclosed within a

single quotes( ' ). Ex. ‘#’ b. Character constant should contain at most one character c. A string constant is a sequence of characters enclosed within double quotes. d. A character constant has an equivalent integer value but the string constants does not have the

equal value. e. Escape sequences can be used to substitute the additional double quote in string constant. For

example “My father\”s aim was to educate me well”, this is equivalent to My father”s aim was to educate me well.

Example The following table shows some of the valid and invalid constants with reason.

Constant Valid/Invalid Reason 458921U Valid U represents unsigned integer constant 15,234 Invalid Comma is not allowed -99.8797 Valid Real constant 25.756e-05 Valid Exponential form 5.5e 4 Invalid Blank space is not allowed #78.45 Invalid Special character is not allowed 0XAB78 Valid Hexadecimal integer -67543 Invalid Beyond the range of integer 89.56e9.6 Invalid Exponent value must be integer 41e8 Valid Exponential form 834343L Valid Long integer form 2343.44.4 Invalid Two decimal points are not allowed

Table 3.5 1.5 Data types Data is a fact about people or a thing. Data types of C++ language are mainly used to classify the data into different category for its storage and retrieval in memory. The memory requirement of data type decides the possible range of values for that particular type of variable or constant. The following table summarizes the different data types that can be used for both variables and constants as described in the previous sections. Data type Bytes

required Purpose Range of values

char 1 (8 bits) To store a single character Any single character short int 1 (8 bits) To represent small integer -128 to 127 int 2 (16 bits) To represent integer quantity -32768 to 32767 unsigned int

2 (16 bits) To represent only positive integers 0 to 65535

long int 4 (32 bits) To represent big integer numbers -231 to 2 31-1 float 4 (32 bits) To represent a floating point

number ( precision is 8 digits) 3.4e-38 to 3.4e+38

Double 8 (64 bits) To represent a very big or small real number( precision is 16 digits)

A real number with 16 digits precision.


1.6 Operators Operators play an important role in the expressions. It combines operators, variables, constants, array elements and function references to form an expression. The data elements that operate on operators are called operands. Most of the operators require two operands and some operators can operate on single operand also. The different categories of operators are as follows a. Arithmetic operators b. Relational operators c. Logical operators d. Unary operators e. Assignment operators The operators of each category are explained below. a. Arithmetic operators All of the mathematical operations are performed using the arithmetic operators. The following table summarizes the arithmetic operators

Purpose Operator Example Addition + a+b Subtraction - c-d-e Multiplication * A*b*d Division / b/10 Remainder (after integer division)

% 10%3

Table 4.1 Example 1 Suppose that a and b are integer variables whose values are 25 and 10 respectively. Let us evaluate the following expressions

Expression Result A+b 35

a-b-10 5 a*b*2 500 A/b 2.5

10%3 5 Example 2 Represent the following mathematical expression in C++ language. Also specify the invalid format.

S.No. Mathematical expression C++ Language format Invalid format 1. Multiply x with –y x* (-y) x*-y 2. Add –x with –y (-x)+(-y) -x+-y 3. ab/c a*b/c Ab/c 4. ax2+bx+c a*x*x+b*x+c ax2+b*x+c 5. a-b / c*d (a-b)/(c*d) a-b/c*d

Table 4.2 Some important points about arithmetic operators a. C++ does not support foe exponentiation, so POW function can be used to calculate power

value.


b. No two consecutive operators are allowed. For example –x+-y is not valid, however you can write it as –x+(-y)

c. Integer Arithmetic

If two operands are integers then the operation is called integer arithmetic and the result obtained will also be the integer. The result of 16/5 is 3, not 3.2, since the decimal point is truncated.

d. Real arithmetic The operation involving real operands is called real arithmetic. The result of 10.0/3.0 is 3.333

e. Mixed-mode arithmetic

In an expression, if one operand is real and the other is integer then it is called mixed mode arithmetic. But the result of the expression is float. For example the result of 150/10.0 is 14.22

b. Relational operators Relational operators are used to compare two quantities such as constants, variables and arithmetic expressions. The result of relational operator is either true or false. If the result of the operator is true then it returns the value as non-zero, otherwise it gives the result as 0. The uses of various relational operators are given below.

Purpose Operator Example Greater than > a>b Less than < age<18 Greater than or equal to >= Mark>=35 Less than or equal to <= x<=y Equal to == x==20 Not equal to != x!=y

Table 4.3 Example Suppose that a and b are two variables whose values are 25 and 75 respectively. Evaluate the following operations. a. a>b, (25>75) the result of this condition is false b. a<(b+50), the result of this condition is true because 25 < (75+50) is true c. (a+b)==100, the result is true since (75+25) is equal to 100. d. (a!=b), the result is true since 25 is not equal to 75. Logical operators C++ language provides three logical operators such as and (&&), or (||) and not (!). These operators are mainly used to combine two or more relational expressions. The operator not (!) is used to negate the given quantity or expression. It takes a single operand. The result of the relational expression is either true or false. The following table summarizes the logical operators

Purpose Operator Example Combine both && (a>b)&&(a>c) Either or || (sex==”f”)||(age>18) Negate the quantity ! !(x==5)

Table 4.3


Example Write the following problems in C++ expression form using relational and logical operators a. both maths and science are greater than 70

Ans: maths>70 && science>70 b. either basic pay >7000 or net salary > 10000

Ans: (basicpay>7000) || (netsalary>10000) c. if not grade is equal to ‘D’

Ans: !(grade==”D”) The following truth table gives the result of logical expression containing logical operators

A B A && B A || B !A

True True True True False True False False True False False True False True True False False False False True

Table 4.4 Unary operators It is a special kind of operators and these are not available in other languages like BASIC, COBOL, FORTRAN etc. The operators so far discussed takes two operands but unary operator takes only one operand for its execution. The following table gives the used of three different unary operators

Purpose Operator Increment ++ Decrement --

Unary minus - The logical operator ! (not) also works like unary operator. The increment operator ++ increments the value of the variables by one, similarly the decrement operator decreases the value by one. The unary minus operator is used to negate the operand and it can be used as predecessor to the operand. The increment and decrement operators can be used either before or after the operands. Let us consider two examples for both the operators. Example 1 Example 2 kal=16; kal = 16; pn=kal++; pn=++kal; In the second line of Example 1, the value of kal is first assigned to the variable pn and then the value of kal is incrementted. So the value of pn is 16 and kal is 17. In the second line of Example 2, the value of kal is first incremented and then assigned to the variable pn. So the value of kal is 17 and pn is 17. The equivalent statement for increment operator is as follows a. pn=kal++; is equal to pn = kal; kal = kal+1; b. pn=++kal; is equal to kal = kal+1; pn = kal;


Assignment operator This operator is mainly used to store the result of an expression to a variable. This follows right to left associative while executive the expression. The common assignment operator is = (equal to ) sign. The general format of assignment operator is as follows Variable op = Expression Where op is a binary operator and it is also known as short hand assignment operator. The above syntax is equal to Variable = Variable op Expression For example, x = x+5 can be written as x+=5. The shorthand operator method of writing expression is more efficient, simplifies the expression and easy to read. Note: Assigning same value to more than one variable is known as multiple assignment statement. Example a=b=c=23; it assigns the value 23 to the variables a, b and c. Suppose that a and b are two integer variables whose values are 10 and 5 respectively. The following table gives the result of various expressions involving shorthand operator.

Short hand expression Equivalent simple expression Result a+=b a=a+10 15 a-=10 a=a-10 0

a*=(a+b) a=a*(a+b) 150 a%=b a=a%b 0 b/=2.5 b=b/2.5 2 a*=a a=a*a 100

Conditional operator It replaces the if..else construct by a single line using conditional operator. An expression consisting of ternary operators (? : ) is called conditional operator. The general format of this expression e1 ? e2 : e3 where e1, e2 and e3 are called expressions. Here e1 must produce the result as either true ( non zero ) or false (0). Execution: First the expression e1 is evaluated. If the result of e1 is true then e2 is executed, otherwise e3 is executed. You can also assign the result of either e2 or e3 to a variable in the following format Variable = e1 ? e2 : e3 Here if the result of the expression e1 is true then e2 is evaluated and its value is assigned to variable at the left side. Examples 1. (age>18)?printf(“\nEligible for voting”):printf(“\nNot eligible for voting”);

Suppose if the condition is true then the output is “Eligible for voting”, otherwise the result is “Not eligible for voting”.

2. bonus = (sal>5000)?2500:3500

If the condition, ie. Sal>5000, is true then the value 2500 is assigned to the variable bonus, otherwise 3500 is assigned to bonus.


1.7 Expressions Expressions are the backbone for any type of calculations in the program. It consists of two or more operands with one or more operators. Every operator requires minimum two operands for its execution (except unary operators and not(!) operator). It is interesting to note that all such expressions are executed in ALU device of CPU. Expressions make use of several quantities such as operands, variables, constants, function references etc. In C++ language, expressions are classified into the following three categories. They are

a. Arithmetic expressions b. Relational expressions c. Logical expressions

Let us discuss each of these expressions in detail Arithmetic expression It represents the mathematical expressions in easy manner. Arithmetic expressions combine arithmetic operators with variables, constants or any other quantities. The result of the arithmetic expression is always a finite number. The general format of this expression is as follows Operand1 <AO> Operand2 Where operand1 and operand2 can be variables, constants or it can be the reference of any function. The arithmetic expression in the assignment statement form is as follows Variable = Arithmetic Expression Let us consider some of the mathematical expressions and its equivalent C++ expressions.

Mathematical expression

C++ language expression

ax2+bx+c

a*x*x+b*x+c

-b --- 2a

-b/(2*a)

a b c --- + --- + --- b c d

a/b + b/c + c/d

b2-4ac

sqrt(b*b-4*a*c)

x1/4

pow(x,1/4)

It is necessary to assign value for the variables before it is used in the expression. Hierarchy of Arithmetic expressions The order followed in executing the operators in an expression is as follows a. Arithmetic expression is evaluated from left to right b. Expressions in innermost parenthesis is executed


c. Function references are executed d. Multiplication and division is performed e. Finally addition and subtraction is performed. Example Consider the following expression for the values of a=5, b=3 and c=2. Y = a/c + b*c - ( a%b ) + b/c Let us calculate the value of Y using the hierarchy rule Step 1: Y = 5/3 + 3*2 – (5%3) + 3/2 Step 2: Y = 5/3 + 3*2 – 2 + 3/2 Step 3: Y = 1.6 + 6 – 2 +1.5 Step 4: Y= 9.1 – 2 The result is 7.1 Relational Expression An expression consisting of operands and relational operator is termed as relational expression. It helps to compare two quantities and produces the result as either true (non-zero) or false (zero). The general format of relational expression is Operand1 <RO> Operand2 Where operand1 and operand2 can be a variable, constants or arithmetic expressions and RO is relational operator. Note: If an operand is arithmetic expression, first it is evaluated then the result is compared. Example Let us consider a=20, b= 10 and c=5. Evaluate the following relational expression and find the final result of each. Relational expression Execution Result a>b 10>20 True a>(b+c) 20>(10+5) True 5*b < (a+c) 50<(20+15) False a2+b2 > (a+b)2 500>900 False Logical expression It is also called as Boolean expression, since this expression also produces the result as either true or false. It compares two relational expressions. The general format of logical expression is Operand1 <LO> Operand2 Where operand1 and operand2 are the relational expressions and LO is a logical operator. The operands of logical expression must produce the result as either true or false. Example Let a=5, b=7 and c=20. Evaluate the following relational expression and find the result.


Logical expression Execution Result (a+b)>c && b>c False && True False a<b || b<c False || Flase False b>a && b>c True && True True Note: Both relational and logical expressions are used with decision statements such as IF, do…while and while statements. 1.8 Structure of a C++ program The lessons so far you have studied dealt with the basics of C++ language such as constants, variables, operators and expressions. Let us turn our focus towards the programming side. As you studied earlier, program is nothing but set of instructions that solves a problem. A program in C++ language consists of set of blocks or sections. The structure of a C++ program is given below.

Sections Contents Header section Comments, definitions and includes

etc. Declaration section Variables and function declaration Executable statements section

Statements, instructions, function calling etc.

Functions/Subprograms User defined functions

Body of the loop

In the above structure, only the body of the program is compulsory and the other sections are optional. The structure of the body of the program is as follows main() { declaration of variable; ------ ------ Instruction/executable part; } Let us consider an example program to illustrate the structure of a C++ program Program: To find the area and circumference of a circle. #include <iostream.h> #include <conio.h> Header section #define phi 3.14 main() { float radius, area, cir; -- Declaration section clrscr(); cout<<“\nEnter the radius value :”; cin>>radius; area=phi*r*r; cir=2*phi*r; Executable statements section cout<<“\nThe area of the circle is = “<<area; cout<<“\nThe circumference of a circle = “<<cir; getch(); } Do you find it difficult to understand? No problem, You will learn all commands and formats in the forthcoming lessons.


1.9 Turbo screen layout Turbo C++ contains a built-in screen editor as part of the compiler. The basic environment of Turbo C++ is called Integrated Development Environment (IDE). It provides various tools like menu bar, status bar, scroll bar and editing area at one screen. The starting screen of turbo C++ is loaded by giving the command tc from the turbo C++ files folder (Usually TC folder). Some of the important commands of Turbo C++ are as follows

Key/Command Purpose F10 To activate the menu bar

F2 / Alt+FSave To save a file F3 / Alt+FL Load a file

Alt+FN To create a new file Alt+X Exit turbo C++ editor

F1 To get help facility about Turbo c F9 To compile a source file

Ctrl+F9 To compile and run a file Select FileOS Shell to exit from C++ temporarily and goes to the DOS prompt. By typing EXIT, it returns to the Turbo editor. By default the turbo editor gives the file name as NONAME.CPP, you can change the name of the file while saving the file. Steps involved while running a program A C++ compiler is system software that converts a C++ program into machine language program. It helps to create the executable version of a program. The steps involved in compilation process is as follows a. Source code creation b. Compiling c. Linking d. Executing Every step uses several programs of C++ compiler to complete the step. Source code creation Source code is a program consisting of statements of C++ language. It is created in turbo editor with an extension .CPP. Example: average.c Compiling A source program is compiled to debug the errors, if any errors are occurred then that is displayed in the screen. After removing all the errors, an object file with an extension .obj is created. It is also called as intermediate file. Example: average.obj Linking It is the process of linking the object code with the code of the library functions that are used by the same program. The resultant file is called executable file and that has the extension as .EXE Example: average.exe Executing Once the EXE file is created it can run in any folder on any machine without the help of turbo C++ compiler also. To execute a file, just type the name of the file (eg. c:\>average) in the prompt.


2. STATEMENTS An instruction with its parameter is called as statements in C++ language. These are placed in the body of the program or function. The instructions of C++ language are classified into three types such as input, processing and output. The term input refers to reading data from the standard input devices, processing refers to set of executable statements for calculation and output refers to producing result on standard output device. Some of the functions for each of this category are described here. 2.1 Input and output statements Input function C++ language provides set of functions for assigning value to the variables. Data can be supplied to the variables in the following ways a. Assignment statement b. cin function In the assignment method values are directly assigned to the variables in the program itself. For example, r=5.5, phi=3.14 etc. The second cin function method helps to supply data in an interactive method at the run time of the program. cin>> function The cin (Console Input) function is used to accept input from the user to the variables. It is made available to the program by including <iostream.h>. It uses extraction operator (>>) to assign data into the variable. The syntax of cin function is

cin>>v1>>v2>>v3; where v1, v2 and v3 are variables for which data will be given. Example int x,y; cout << "Enter two numbers : "; cin>>x>>y; Entering data While giving data to the variables of cin statements, data must be separated by blank space(s) or by separate line. Let a=10, b=20, c=12.75 and d=”NETHRA”. The different ways to supply data for the variables of scanf are as follows

Scanf statement format Data input methods cin>>a>>b>>c 10 20 12.75 or 10 20 or 10

12.75 20 12.75

cin>>a>>c>>d 10 12.75 NETHRA Rules for cin statement Variable must be separated by >> sign Data reading is aborted when data does not match to the variables The data which are not read in the current line is assigned to the next cin statement


Output statement Output statements are used to display the result of any calculation in the screen, file or printer. The most common output statement used in C++ language is cout function. cout function It is a standard output function in C++ language. It is used to display the captions (messages) and the result of any numerical calculations. This function transforms the result or data from the memory to the standard output device. The general format of printf function is as follows cout<<”Message” or cout<<”Message”<<variable The insertion operator(<<) inserts the data that follows into the standard console device (eg.Monitor) here Message can be any text enclosed in double quotes(“ “) and the variable refers to the name of the variable whose value is to be printed. The escape sequence of characters like \n, \t, \b etc. can be used to get appropriate space etc in the output. Some of the control string characters are as follows \n -- to print data in a new line \t -- to leave one tab space ( normally 5 spaces) \a -- to create beep sound Example: cout<<”\n Hello Everybody……”; cout<<”\n My name is “<<name<<” and I am studying in “<<class<<” th standard”; cout<<”\nResult : a \t b”; cout<<a<<”\t”<<b; 2.2 Control statements Programs so far we discussed use simple statements and every statement is executed only once. But in some circumstances it may be required to repeat set of statements depending upon the condition being tested. The control statements of C++ language helps to decide the order of the execution based on certain condition. These statements can be used mainly for the following purpose Branching After performing logical test, the appropriate block of statements is executed based on the result of the logical test. This is known as branching. Example: If…else statement Selection It is a special kind of branching that selects one group of statements from the available set of statements. Example: Switch…case Looping The set of statements is repeated continuously until the given logical condition is satisfied. Example: for statement, while and do…while


2.3 The if-else statement It is a logical conditional statement, which uses either relational or logical expression. It executes one of the two possible block of statements based on the result of the condition given in the if statement. The general format of if statement is as follows if (condition) { statement part-1; } statement part-2; Condition is either relational or logical expression and it must be placed in parenthesis and the statement parts contain one or more executable C++ statement. Flowchart

is True condition ? Statement part-1

False Statement part-2 Execution First the expression is evaluated to check whether it is true (non-zero) or false (zero) and then the statement part 1 is executed if the value is true, otherwise the statement part 2 is executed. Example a. if (age>18) printf(“\n Eligible for voting”); b. if(mark1<35 || mark2<35 || mark3<35) printf(“\nThe result is fail”); c. if((a>b)&&(a>c))

{ big=a;}

d. if ((b*b-4*a*c)>0) { x1=(-b+ sqrt(d))/2*a; x2=(-b-sqrt(d))/2*a; printf(“root 1= %f root 2 = %f”,x1,x2); }

e. if ((strcmp(result,”PASS”)==0) && average>75)

printf(“You got distinction”);


if-else format The extended version of if statement is the if-else format. The general format is as follows

if (condition) { statement part-1; } else { statement part-2; } statement part-3; Execution After evaluating the condition of if statement, if the result is true then the statement part-1 is executed and then control is transferred to statement part-3. If the result of the expression is false then it executes the statement part-2 and then it goes to statement part-3. Flowchart for if-else is condition Statement part-1 ? True False Statement part-2 Statement part-3 Example a. if(b>c) printf(“\nB is the biggest number”); else printf(“\nC is the biggest number”); b. if(sex==’M’)

{ tax = (grosspay-70000)*20/100; } else tax=0.0

c. if(n==0) printf(“The number is zero”); else

printf(“The number is non-zero”); d. if(n%2 ==0)

printf(“\n The given number is even”); else printf(“\n The given number is odd);


Nested if-else statement An if-else statement within another if statement is called nested if statement. You can nest any number of if statements in if part, else part or in both. The two different nested if statement is as follows

Syntax 1 if (condition-1) { if(condition-2) { statements; } else { statements; } } else { statements; }

Syntax 2 if (condition-1) { statements; } else { if(condition-2) { statements; } else { statements; } }

Rules of if-else statement The condition of the if statement should be either relational or logical expression. The result

of the condition should be either zero(false) or non-zero(true) Statements can be either single or compound. In case of more than one statements enclose

within the braces ({ }). The else part is optional in if statement Any number of nesting is allowed If condition contains more than one clause in expression then it must be given in parenthesis. 2.4 The switch Statement The switch statement is a multiple branching statement. A single switch statement can be used to replace the nested if statements. It helps to select a particular group of statements among several groups of statements. This selection is based on the expression given in the switch statement. The general format of switch statement is as follows switch(exp) { case v1 : …….. break; case v2 : …….. break; case vn : …….. break; default : …….. break; }


In switch statement exp stands for expression, it can be a variable or arithmetic expression but the result should be a integer value. The case labels (prefixes) v1, v2…vn cab be a integer value or character constant. Execution First the value of the expression is calculated and then it is compared with the case label starting from v1 to vn. If a match is found then the set of statements of that case label is executed till the break statement. If no match is found in between v1 to vn then the statements given in default part will be executed. The default statement is optional. The break statement is used to exit out of switch statement and the control is passed to the following statement of switch. Rules of switch statement The expression in switch statement must produce the result as integer value. If it is a

character type then the equivalent integer value is considered Break statement between case labels transfers control out of switch statement, otherwise it

executes the consecutive case blocks also If none of the case labels are matching with case expression then the default part is executed The case labels must be unique Switch is an alternate statement for nested if statement 3. Control statements 3.1 The While statement It is a looping statement that executes set of statements repeatedly until some condition has been satisfied. The general format of while statement is while (condition) { ……… statements;

……… } Condition is a relational or logical expression that should produce the result as either true or false. The statements in the body of the loop are an executable statement(s), which can be simple or compound statement. In case of more than one statement, it should be enclosed in the curly braces. Execution The statements in the body of the loop are executed repeatedly as long as the condition in the while statement is true ( non zero ). If the condition becomes false then it goes to the statement following the while statement.


Flowchart is False condition ? True

Statement in body of the loop

Rules of while statement Condition in while should produce the result as either true or false More than one statement in the body of the loop must be enclosed in braces Break statement can be used to come out of while if necessary. 3.2 The do-while statement This is also a looping statement similar to while statement except that the condition is placed at the end of the loop. So it is assured that at least one time the body of the loop is executed. The general format of do-while statement is do { ……… statements;

……… } while (condition); Condition is a relational or logical expression that should produce the result as either true or false. A semicolon must be given at the end of the condition. Execution First the statements in the body of the loop are executed then the condition is tested. If it is true then again the body of the loop is executed. This is repeated continuously as long as the condition in the while statement is true ( non zero ). If the condition becomes false then it goes to the statement following the while statement. Flowchart

Statement in body of the loop

True is condition? False


Difference between while and do-while

While do-while Condition is placed at the beginning of the loop

Condition is placed at the end of the loop

Body of the loop is executed only when condition is true

At least once the body of the loop is executed without testing condition

It is used more frequently in many programs

Used rarely

3.3 The for Statement The for loop is the most commonly used statement in many programs for repeated calculations. It increments the counter variable automatically. The for loop works well where the number of iterations of the loop is known before the loop is entered. The general format of for statement is

for (exp1;exp2;exp3) {

………….

statements …………. }

exp1, exp2 and exp3 are the expressions and these are called loop controlled parameters. The for statement consists of three important parameters namely initialization (exp1), test condition (exp2) and increment(exp3). If the statement block is only one statement, the braces are not necessary. The following code will print AEJC, MUMBAI times:

for (i=0; i<10; i++) printf("\n AEJC, MUMBAI "); Flowchart of for loop

control= exp1/Variable is Condition exp1 vs exp2 ? False True Execute the body of the loop control = increment exp1 variable with exp3


Execution

a. First the expression-1 of for loop is evaluated ie. initial value is assigned to index or control variable

b. The value of index variable is tested with expression-2

c. If the result of above step is true then the body of the loop is executed, otherwise the control is transferred to the statement that follows for loop.

d. Now the index value is incremented with the help of expression-3. Go to step (b) and repeat this procedure as long as the condition is true.

3.4 Rules of for loop 1. More than one variable can be initialized in the for loop separated by commas.

Example: for(i=0,j=5; j<10;i++,j++) printf(“%d %d”,i,j);

2. Expression-2 in the for loop is called test condition and it can be a compound relational or

logical expression. Example: for(i=10,j=100; i<=100 && j>10;i++,j--) printf(“%d %d”,i,j);

3. We can also omit one or more expressions in the for loop

Example 1 Example 2 Example 3 i=0; i=0; i=0;

for(; i<=10;i++) for(; i<=10;) for(; ;) printf(“%d”,i); { printf(“%d”,i); { printf(“%d”,i); i++; } i++; if(i>100) break; } 4. A for loop can be used to create time delay in the program by executing null statement

Example: for(i=0;i<=1000;i++); here the body of the loop contains just semicolon (;). It is called null statement.

5. A for loop without any section and without break point in the body of the loop is called as

indefinite loop. Example: i=10; for( ; ; )

{printf(“%d”,i); i++); The body of the loop does not contain break, so loop is never terminated 6. A for loop within another for loop is termed as nested loop.

Example for(i=0;i<5;i++) { for(j=1;j<10;j++)

{ printf(“%d %d”,i,j); Inner loop Outer loop }

}


7. Every for statement in the nested loop should have unique index variable. Example for(i=0;i<5;i++) { for(i=1;i<10;i++) This is not valid

{ printf(“%d %d”,i,i); }

8. Control can be transferred at any point from the for loop to some other part of the program

using break statement. Example for(i=1;i<=10;i++) { printf(“%d”,i); if((i%7)==0) break; }

Break vs Continue The continue statement can be used in any loop statement like break. On executing break statement, the control is transferred out of the loop. But the continue statement is used to skip the remaining part of the loop and continues with the next cycle or iteration of the same loop. Example 1 Example 2 for(i=0;i<=20;i++) for(i=0;i<=20;i++) { { if(i%3!=0) if((i%3)==0) continue; break; else else printf(“%d”,i); printf(“%d”,i); } } On executing example 1 coding, it produces the result as 3, 6, 9, 12, 15 and 18. The second example produces the result as 0, 1 and 2. 4. Functions 4.1 Library functions The C++ language supports for several types of library functions for variety of purposes. These functions also called as built-in functions or ready-made functions. Every function is a pre-written program that is stored in the form of header files. The compiler of C++ language evaluates these functions when called in the program and the results are returned. The general format of library function is function(arguments) Every function requires arguments that can be a variable, constant or expression. The result type of a function varies from function to function. Some of the common header files are as follows

S.No Header file Used for Example functions 1. <iostream.h> Standard input and output functions cin / cout 2. <conio.h> Console input and output functions getch, clrscr, gotoxy 3. <math.h> Mathematical and trigonometric

functions abs, sqrt, pow

4. <string.h> String manipulation functions strlen, strcpy, strcat 5. <stdlib.h> Standard library functions rand, exit, atof 6. <time.h> Time related functions time, difftime, clock


Some of the most useful library functions are explained. 1. sqrt function This function is used to find the square root of the given value. The argument of the sqrt function must be a non-negative real quantity. The general format is sqrt(x). Suppose that if the value of x is negative number then the C++ compiler produces the error message. Example a. sqrt(81.0) gives the result as 9.0 b. sqrt(b*b-4*a*c) 2. abs function It produces the absolute value of the given number. If the number is negative then it gives the equivalent positive number. Suppose that if the argument is a positive number then it remains same. The general format of the abs function is abs(x), where x is a integer number. Example a. abs(-232), the result is 232 b. abs(456), the result is 456 c. The result of abs(0) is 0 Note: The function fabs() is used to find the absolute value of the floating point number. 3. pow function The function pow stands for power. The general format of this command is pow(x,y), where x and y are of floating point numbers. The pow(x,y) is equivalent to xy Example a. pow(3.0,3.0) gives the result as 27.0 b. x=5, pow(x+2,2) gives the result as 49.0 4. fmod function This function is used to find the remainder of a number divided by another number. The general format of this function is fmod(x,y) where the arguments are float numbers. It divides the value of x by y and gives the remainder as result. Example a. fmod(99.0,10.0) produces the result as 9 b. fmod(100,10.0) gives the result as 0.0 5. ceil function It returns the ceiling value, that is, the smallest integer greater than or equal to the given number. The general format of this command is ceil(x), where x is a floating point number. Example a. ceil(7.9) gives the result as 8 b. ceil(-5.6) gives the result as –5 6. rand function It returns a random number as the result. A random number is a number, which cannot be predicted. It is used in several places where the samples are to be tested with large number of data. The general format of the function is rand(), the important point to note here is that it does not take any parameter.


Example a. rand() gives the value as 346, it depends upon the machine and compiler. Note: The function srand(x) is used to initialize the random number with a seed value, so that for every seed it generates a different random number. Example a. srand(645)

rand() gives the result as 26759 b. srand(3455)

rand() gives the result as 16837 7. Trigonometric functions Some of the trigonometric functions and usage are given below S.No Function

name Argument type Used for Example

1. sin(x) Real value in the form of radians

To find the sine value of x

2. cos(x) --do-- To find the cosine value of y 3. tan(x) --do-- To find the tangent value of x 4. exp(x) Real value Calculates exponent value of x

User Defined Function / Functions in C++ A function in C++ allows the user to define own functions. A function is defined in some part of the program with block of statements and it can be called from any part of the program. It helps to implement the modular programming concept in the programming.The general format of the function is as follows Data_type name ( parameter1, parameter2, ...) { ………….

statements …………. } data_type is the data type of the result to be returned, void indicates it returns NULL. name is the name of the function by which it will be possible to call the function. Parameters are the variables that receive data from the calling place. All parameters must

be separated by commas and declared by the corresponding data type. statements is the body of the function and it must be enclosed by {}

Function Prototype It is the declaration of the function at the beginning of the program with its data-type, name of the function and parameters followed by semicolon. The body of the function need not be given. It helps to instruct the compiler that the actual function definition may be defined in some other point of the program. The general format of the function is Data_type name ( parameter1, parameter2, ...); In the place of parameter, the name of the variable is optional, hence only data type can also be specified.


Function call A function can be called from any part of the program just by the name of the function with its proper arguments. Same function can be called any number of times in the program as follows Variable = name(arguments) or name(arguments); Name refers to the name of the function and arguments refer to the name of the variable, constants or simple expressions. Eg. fact(n); ncr=fact(n)/(fact(r)*fact(n-r)); Return statement It returns the result to the calling place of the program. The data type of the value to be returned is decided based on the data type given in the declaration of the function. A program can have any number of return statements but it can return only one value at a time (ie. For Each call) A function with void data type cannot return any value. Scope of the variables The visibility of the variables in the function or program is termed as scope of the variable. It refers to the availability of the variables in different parts of the program. Example: #include<iostream.> int factorial(int k); ------- Function prototype void main () { int n,fact; cout <<"Enter the number whose factorial has to be calculated" << endl; cin >> n1; fact=factorial(n); ------ call to function factorial cout << "The factorial of " << n << " is : " << fact << endl; return(0); } int factorial(int k) ------- function declaration { int i=0,f=1; if(n<=1) { return(1); } --- return statement with a value else { for(i=1;i<=k;i++) { f=f*i; } return(f); --- return statement with a value } }

Documents

C++ Introduction