C++ Fundamentals
73
FUNDAMENTALS OF C++
description
c++
Transcript of C++ Fundamentals
FUNDAMENTALS OF C++
Objective
• Become familiar with fundamental tokens and data types
• Write simple computer program in C++
• Use simple Output statements
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History of C C is a high level language.
Evolved by Dennis Ritchie and Brain Kernighan(1978)
from two previous programming languages, BCPL (Basic Combined
Programming Language )and B
Used to develop UNIX system software routines
Is implemented on UNIX operating system
Structural / Modular Programming
Portable & have compilers for almost all architectures.
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C++ “C with classes” (1979) C++ (1983)
Superset of C developed by Bjarne Stroustrup at Bell Labs and provides
object-oriented capabilities named “c with classes”.
Object-oriented design is very powerful
10 to 100 fold increase in productivity
Dominant language in industry and academia.
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Simple C++ program // Display “This is my first C++ program”
// Single line comment
#include <iostream.h> // preprocessor directive
void main( ) // Entry point for program execution
{ // block of statements: Begin
clrscr( ); //Each Statement ends with ;
cout << “This is my first C++ program”;
} // block of statements: End
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Simple C++ Programs.. // Multi lines comment /* Find the avg. of three marks and display pass or fail */ #include <iostream.h> void main() { cout << “Enter Roll Number and marks of three subjects”; int RollNo,marks1, marks2, marks3; float avg = 0; const minimum = 35.0; cin >> marks1>> marks2>> marks3; avg = (marks1+marks2+marks3)/3; if (avg < minimum ) cout << RollNo <<“ fail”<< end; else cout << RollNo << “pass”<<end; }
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Consists of letters, digits, special characters, white
spaces.
(i) Letters ‘a’, ‘b’, ‘c’,………..z Or
‘A’, ‘B’, ‘C’,……….Z
(ii) Digits 0, 1, 2,……………………9
(iii) Special characters ;, ?, >, <, &,{, }, [, ]……
(iv) White spaces ex. New line (\n)
The C++ Character Set
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C++ Tokens
Tokens
Keywords Identifiers Operators Strings constants Special
Symbols
Keywords words that are basically sequence of
characters defined by a computer language that have one
or more fixed meanings. They are also called as reserve
words. Key words cannot be changed.
ex. int, float, do-while, if, else,…………..
Keywords Each keyword has a predefined purpose in the language.
Do not use keywords as variable and constant names!!
Some of the C/C++ keywords are
auto, bool, break, case, catch, class, char, const,
continue, do, default, delete, double, else,
extern, enum, false, float, for, friend, goto, if,
int, inline, long, namespace, new, operator,
private, protected, public, register, return,
short, static, struct, sizeof, switch, template,
this, throw, try, typedef, true, unsigned, virtual,
void, volatile, while …
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Identifiers allow us to name data and other objects in
the program.
Each piece of data is stored at unique address instead of
using addresses, names are used
Example: user defined names like
int amount, float avg, …
Operators +, -, *, %, /, …
Strings “Manipal”
Constants -15, 10
Special Symbols { } (, …
C++ Tokens
Identifiers
An identifier is a name for a variable, constant, function, etc.
It consists of a letter followed by any sequence of letters, digits, and underscores.
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Identifiers – rules
A valid identifier is a sequence of one or more letters, digits or underscore character (_).
Neither spaces nor punctuation marks or symbols can be part of an identifier
Only letters, digits and underline characters are valid
variable identifiers always have to begin with a letter
They can also begin with an underscore character (_ ), but this is usually reserved for compiler specific keywords or external identifiers.
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Identifiers – rules
They can not begin with a digit.
The C/C++ is a "case sensitive" language.
An identifier written in capital letters is not equivalent to another one with the same name but written in small letters.
The “RESULT” variable is not the same as the “result” variable or the “Result” variable
They cannot match any keyword of the C++ language or your compiler's specific ones since they could be confused with these.
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Identifiers
Examples of valid identifiers: First_name, age, y2000, y2k
Examples of invalid identifiers: 2000y
Identifiers cannot have special characters in them. For example: X=Y, J-20, ~Ricky,*Michael are invalid identifiers.
Identifiers are case-sensitive.
For example: Hello, hello, WHOAMI, WhoAmI, whoami are unique identifiers.
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A value that IS NOT going to be changed during the execution of our program;
Constant are specific values that are used in arithmetic expressions or assigned to variables, e.g. 2, 5, -10, 2.e+6, 3.14159, and so forth;
Sometimes a constant represents truly a constant value in nature such as:
Pi 3.14159
speed of light 2.99792+E8 meters/sec
Constants
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Constants
Numeric Constants
Integer constants
Real Constants
Character Constants
Single character constants
String constants
Constants
Numeric Constants Integer Constants
Refers to a sequence of digits.
Decimal, Octal , Hexadecimal.
Decimal: set of digits 0 to 9, preceded by optional “–” or “+” sign
Octal: digits 0 to 7 with a leading “0”
Hexadecimal: digits 0 to 9, char A to F preceded by “0x”
E.g.: 143, -564, 0346, 0x34, 0x8AF
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Floating Point Constant Used to represent numbers with fractional part
E.g.; 213.45, .456,234.
Another form mantissa e exponent
0.56e4, 3.12E4 , -4.6E-1
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Character Constants Single character
Single character with in a pair of single quote (‘ ’) marks, having integer values known as ASCII values.
E.g.: ‘d’, ‘t’, ‘9’
String Constants A sequence of characters enclosed in double quotes
(“ ”). Characters may be letters, numbers, special characters and blank space.
E.g.: “hello”, “2007”, “T”, “4+5”
Backslash character constants
Used in output functions
E.g.: ‘\n’ new line, ‘\0’ null char, ‘\a’, ‘\b’, ‘\t’, ‘\”’ …
Also known as escape characters.
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A variable is a data name that may be used to
store a data value.
A variable may take different values at different
times during execution.
Variable name chosen by the programmer in a
meaningful way.
Each variable needs an identifier that
distinguishes it from the others.
( rules similar to identifier)
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Variables
C++ data Types
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C++ Data Types
User Defined Type Structure, Union, Class
enumeration Built-in-type
Integral type
int char
void Floating Type
float double
Derived Type Array, Function, Pointer
Data types
C++ Language is rich in its data types
Mainly 4 classes of data types
Primary (fundamental or Built-in type) data types,
User defined Data types
Derived Data types
Empty data set.
The fundamental or Built-in data types fall into one of
three categories
Integer type
Floating-point type
Character type
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Primary (built-in or Basic) Data types
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void
SIGNED TYPE UNSIGNED TYPE INT UNSIGNED INT
SHORT INT UNSIGNED SHORT INT
LONG INT UNSIGNED LONG INT
SIGNED CHARCATER
UNSIGNED CHARACTER
FLOAT
DOUBLE
LONG DOUBLE
INTEGER CHARACTER
FLOATING POINT TYPE
INTEGRAL TYPE
Integer Types The basic integer type is int The size of an int depends on the machine and the
On PCs it is normally 16 or 32 bits
Modifiers short: typically uses less bits
long: typically uses more bits
unsigned
signed
Different types allow programmers to use resources more efficiently.
Standard arithmetic and relational operations are available for these types.
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short int int
long int
SIZE AND RANGE OF VALUES FOR A 16-BIT MACHINE (INTEGER TYPE)
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Type Size (bits)
Range
short
short int or signed short int 8 -128 to 127
unsigned int 8 0 to 255
integer int or signed int 16 -32,768 to 32,767
unsigned int 16 0 to 65,535
long
long int or signed long int 32
-2,147,483,648 to 2,147,483,647
unsigned long int 32 0 to 4,294,967,295
Character Types Character type char is related to the integer types
Modifiers unsigned and signed can be used
char 1 byte(-128 to 127)
signed char 1 byte(-128 to 127)
unsigned char 1 byte(0 to 255)
Characters are encoded using a scheme where an integer represents a particular character
ASCII is the dominant encoding scheme (American Standard Code for Information Interchange )
Examples ' ' encoded as 32 '+' encoded as 43
'A' encoded as 65 'Z' encoded as 90
'a' encoded as 97 'z' encoded as 122
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Floating-Point Types Floating-point types represent real numbers
Integer part
Fractional part
The number 108.1517 breaks down into the following parts
108 - integer part
1517 - fractional part
C provides three floating-point types
float
double
long double
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float double
long double
SIZE AND RANGE OF VALUES FOR 16-BIT MACHINE (FLOATING POINT)
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Type Size Range
Single Precision
float 32 bits 4 bytes
Numbers between 3.4 E-38 and 3.4E+38
Double Precision
double 64 bits 8 bytes
Numbers between 1.7E-308 and 1.7E+308
Long Double Precision
long double 80 bits
10 bytes Numbers between 3.4E-
4932 and1.1E+4932
void
2 uses of void are
To specify the return type of a function when it is not
returning any value
To indicate an empty argument list to a function
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Boolean
• Logical or Boolean data- named after French
Mathematician/philosopher George Boole
• Consists of only two values: true and false
• Nonzero number can be used to represent true
• Zero is used to represent false
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Declaration of variables In order to use a variable in C++, we must first declare it.
It does two things Tells the compiler the variable name.
Specifies the type of data.
Primary Type declaration:
write the specifier of the desired data type (like int, char, float...) followed by a valid variable identifier.
i.e data-type V1, V2,…,Vn
For example:
int a;
float mynumber, sum;
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Declaration of variables The integer data types short, long and int can be either signed
or unsigned depending on the range of numbers needed to be
represented.
Signed types can represent both positive and negative values,
whereas unsigned types can only represent positive values (and
zero).
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Signed and unsigned can be specified by using either
the specifier signed or the specifier unsigned before
the type name.
For example:
unsigned short int NumberOfSisters;
signed int MyAccountBalance
By default most compiler settings will assume the type to
be signed(exception is char).
Declaration of variables
Declaration of variables Short and long can be used alone as type specifiers.
The following two variable declarations are equivalent:
short Year;
short int Year;
Signed and unsigned may also be used as standalone type
specifiers.
The following two declarations are equivalent:
unsigned NextYear;
unsigned int NextYear;
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Declaration of variables
Floating point:
keywords float, double, long double
Character Type:
keywords char, unsigned char, signed char.
Eg:
double deviation;
char p, q;
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Assigning values to variables Values can be assigned using the assignment operator ‘ = ’
It is possible to assign at the time of declaration.
data-type varaiable-name=constant
Eg: initial = 1;
area = 23.89;
int final_value = 100, p = 20;
char yes = ‘m’;
The process of giving initial values to variables “Initialization”.
external & static variables initialized to zero by default.
const int class_size = 40;
const tells the compiler the value of variable class_size must not modified by the program. It can be used on the right hand side of any assignment statement.
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Initialization of variables example
#include <iostream.h>
void main ()
{ int a=5; // initial value = 5
int b;
b=2; // initial value = 2
int result; // initial value undetermined
a = a + 3;
result = a - b;
cout << result;
}
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User defined Type declarations
typedef
Type definition - lets you define your own identifiers.
enum
Enumerated data type - a type with restricted set of
values.
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User defined Type Declaration typedef : general declaration format
typedef type identifier;
The “type” refers to an existing data type and “identifier” refers to the new name given to the data type.
After the declaration as follows:
typedef int marks;
typedef float units;
we can use these to declare variables as shown
marks m1,m2[10]; //m1 & m2[10] are declared as integer variables
units u1, u2; //u1 & u2 are declared as floating point variables
The main advantage of typedef is that we can create meaningful data type names for increasing the readability of the program.
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User defined Type Declaration
enum data type : general declaration format
enum identifier {value1, value2,..,valuen};
The “identifier” is a user defined enumerated data type which can be used to declare variables that can have one of the values known as enumeration constants.
After this declaration as follows:
enum identifier v1,v2,…vn;
enumerated variables v1,v2,..,vn can only have one of the values value1, value2,…,valuen
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User defined Type Declaration E.g.: enum day {Monday, Tuesday,… ,Sunday} ; enum day week_st, week_end; week_st = Monday; week_end= Friday; if(week_st == Tuesday) week_end = Saturday;
Compiler automatically assigns integer starting with 0 to all enumeration constants. But can be overridden.
E.g.: if you give enum day { Monday=1, Tuesday,…, Sunday};
Monday is assigned 1 & subsequent constants incremented by one.
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Which helps us to associate an identifier with a constant value in your program;
The advantage is that you can refer to the identifier any
time you need to use the constant value instead of having
to repeat writing the value;
To declare a symbolic constant you must do it as follows:
const data type identifier = value;
Symbolic Constants
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Consider the Example below:
void main()
{
float area, perimeter;
float radius;
const double Pi = 3.14159;
area = radius * radius * Pi;
perimeter = 2 * Pi * radius;
cout <<“Area equals “<<area
<<“ Perimeter equals “<<perimeter;
}
Symbolic Constant - example
Review of Data Types
What is a data type?
List the different category of data tyes?
Name the types under Built-in Data types.
Discuss the variations of the following:
int, char, float
What is void? Why it is required?
How you can declare variables?
What is initialization? Why it is required?
List the six different steps involved in executing a program.
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Typical C++ Program Development Environment
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Phases of C++ Programs:
1. Edit
2. Preprocess
3. Compile
4. Link
5. Load
6. Execute
A Simple C++ program
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• 1 // Program: first.cpp
• 2 // My first program in C++.
• 3 #include <iostream>
• 4
• 5 // function main begins program execution
• 6 int main()
• 7 {
• 8 cout << "Welcome to C++!\n";
• 9
• 10 return 0; // indicate that program ended successfully
• 11
• 12 } // end function main
Welcome to C++!
Single-line comments.
Preprocessor directive to
include input/output stream
header file <iostream>. Function main appears
exactly once in every C++
program..
Function main returns an
integer value. Left brace { begins function
body.
Corresponding right brace }
ends function body.
Statements end with a semicolon ;.
Stream insertion operator.
Keyword return is one of
several means to exit function; value 0 indicates
program terminated
successfully.
// Program: first.cpp // my first program in C++
These are single line comments.
All lines beginning with two slash signs (//) are
considered comments
They do not have any effect on the behavior of the
program
The programmer can use them to include short
explanations or observations within the source code
itself.
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Comments
#include <iostream.h> Lines beginning with a sign (#) are directives for the
preprocessor.
They are not regular code lines.
directive #include <iostream.h> tells the preprocessor to
include the iostream standard header file.
This specific file (iostream.h) includes the declarations of
the basic standard input-output library in C++, and it is
included because its functionality is going to be used later.
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void main () The main function is the point where all C++ programs start
their execution, independently of its location within the source code.
it is essential that all C++ programs have a main function.
The word main is followed in the code by a pair of parentheses (). That is because it is a function declaration.
Optionally, these parentheses may enclose a list of parameters within them.
Right after these parentheses we can find the body of the main function enclosed in braces{ }.
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cout <<“Welcome to C++!\n”;
This line is a C++ statement.
A statement is a simple or compound expression that can actually produce some effect.
cout represents the standard output stream in C++.
meaning of the entire statement is to insert a sequence of characters into the standard output stream (which is usually the screen).
(;) This character is used to mark the end of the statement and in fact it must be included at the end of all expression statements [other than control structures & main()] in all C++ programs.
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‘cin>>’ Rules ‘>>’ known as extraction or get from operator.
It extracts the value from keyboard & assign it to the variable on its right.
Integer read
Ignores/skips leading white space characters (space, tab, new line)
Begins collecting digits, stops at the first non-digit character (leaving that character in the buffer)
Character read
Ignores/skips leading white space characters (space, tab, new line)
Reads next character (any valid ASCII character)
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‘cin>>’ Rules
String read
Ignores/skips leading white space characters (space, tab,
new line)
Collects characters and stops at the first white space
character
E.g.:
cin>>a; cin>>b>>c;
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‘cout<<’ Operator
‘<<’ is called the insertion or put to operator.
It inserts the contents of the variable on its right to the
object on its left.
E.g.:
cout<<“enter two numbers \n”;
cout<<“Sum =“<<sum<<“\n”;
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A Simple C++ program
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1 // Program: Second.cpp
2 // Printing a line with multiple statements.
3 #include <iostream>
4
5 // function main begins program execution
6 int main()
7 {
8 cout << "Welcome ";
9 cout << "to C++!\n";
10
11 return 0; // indicate that program ended successfully
12
13 } // end function main
Welcome to C++!
Multiple stream
insertion statements
produce one line of
output.
A Simple C++ program
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1 // Program: third.cpp
2 // Printing multiple lines with a single statement
3 #include <iostream>
4
5 // function main begins program execution
6 int main()
7 {
8 cout << "Welcome\nto\n\nC++!\n";
9
10 return 0; // indicate that program ended successfully
11
12 } // end function main
Welcome to C++!
Using newline
characters to print on
multiple lines.
A Simple C++ program
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1 // Program: Add.cpp
2 // Addition program.
3 #include <iostream>
4
5 // function main begins program execution
6 void main()
7 {
8 int integer1; // first number to be input by user
9 int integer2; // second number to be input by user
10 int sum; // variable in which sum will be stored
11
12 cout << "Enter first integer\n"; // prompt
13 cin >> integer1; // read an integer
14
15 cout << "Enter second integer\n"; // prompt
16 cin >> integer2; // read an integer
17
18 sum = integer1 + integer2; // assign result to sum
19
20 cout << "Sum is " << sum << endl; // print sum
21
22 } // end function main
Declare integer
variables.
Use stream extraction
operator with standard
input stream to obtain
user input.
Stream manipulator endl outputs a
newline, then “flushes
output buffer.”
Concatenating, chaining
or cascading stream
insertion operations. Calculations can be performed in output statements:
alternative for lines 18 and 20:
cout << "Sum is " << integer1 + integer2 << endl
Enter first integer
45
Enter second integer
72
Sum is 117
OUTPUT
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Algorithm : read and display a no.
Step1: Read a no.
Step 2: [display it on the screen]
Print ‘the no. is =‘, no.
Step 4: [End of algorithm]
Stop
WAP to read and display a number
Input a no.
Print the no.
Start
Stop
#include<iostream.h> // header file for input/output
#include<conio.h> // header file for clrscr() & getch()
void main() //main function
{ //program body begins
clrscr(); //in-built function
int a; //variable declaration
cout<<“enter number “; // user friendly info display
cin>>a; // reading or input value to the variable
cout<<“\nthe no. is\n”<<a; //writing or output variable value
getch(); } // end of program
Program to read and display a number
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• To convert seconds into hours,minutes & seconds
• To convert Celsius to Fahrenheit & vice versa
Write C++ Programs [algorithm, flowchart & program]
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Algorithm : conversion of secs into hr, min, secs
Step1: Read secs
Step 2: [do conversions]
hr= sec/3600
min= (sec mod 3600)/60
sec= (sec mod 3600) mod 60
Step 3: print ‘hours=‘ hr, ‘minutes=‘ min, ’seconds=‘ sec
Step 4: [End of algorithm]
Stop
WAP to convert seconds into hours, minutes & seconds
hr= sec/3600 min= (sec mod 3600)/60
sec= (sec mod 3600) mod 60
Input sec
Print hr, min and sec
Start
Stop
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#include<iostream.h>
#include<conio.h>
void main( ){
int sec, hr, min;
cout<<“enter seconds”;
cin>>sec;
hr= sec/3600;
min= (sec % 3600)/60;
sec= (sec % 3600) % 60;
cout<<“\n”<<“hour=“<<hr<<“minutes=“<<min;
cout<<“seconds=“<<sec;
}
Program to to convert seconds into
Hours, minutes & seconds
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Algorithm : To convert Celsius to Fahrenheit & vice versa
Step1: Read celsius
Step 2: Fahrenheit =(9.0 / 5.0) * celsius + 32.0
Step 3: Print ‘temp in Fahrenheit=‘ Fahrenheit
Step 4: Read Fahrenheit
Step 5: celsius =(Fahrenheit – 32) * (5.0 / 9)
Step 6: Print ‘temp in celsius=‘ celsius
Step 7: Stop
WAP to convert Celsius to Fahrenheit & vice versa
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Flowchart Read Celsius
Fahrenheit =(9.0 / 5.0) * celsius + 32.0
print Fahrenheit
Read Fahrenheit
celsius =(Fahrenheit – 32) * (5.0 / 9)
Print Celsius
Start
Stop
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#include<iostream.h> #include<conio.h> void main() { float faren , cel;
cout<<“enter temperature in Celsius”;
cin>>cel;
faren=(9.0 / 5.0) * cel + 32.0;
cout<<“fahrenheit =“<<faren;
cout<<“enter temperature in fahrenheit “;
cin>>faren;
cel=(faren – 32) * (5.0 / 9);
cout<<“celsius= “<<cel;
}
Program to convert Celsius to Fahrenheit & vice versa
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• To exchange memory variable a and b
• To display a triangle of * on the screen
• Find the sum of digits of a 4-digit number
Write C++ Programs
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# include<iostream.h>
# include<conio.h>
void main( ) {
int a,b;
cout<<"enter 2 numbers: ";
cin>>a;
cin>>b;
a=a + b;
b=a-b;
a=a-b;
cout<<"after interchange the values are<<a<<"\t"<<b;
}
Program to exchange memory variables a, b
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#include<iostream.h>
#include<conio.h>
void main()
{
clrscr();
cout<<" * ";
cout<<"\n ***";
cout<<"\n *****";
}
Program to display a triangle of *’s on the screen
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#include<iostream.h>
#include<conio.h>
void main(){
clrscr();
int num, digit, sum=0;
cout<<“enter 4 digit no.”;
cin>>num;
digit= num%10;
num=num/10;
sum=sum + digit;
digit= num%10;
num=num/10;
sum=sum + digit;
digit= num%10;
num=num/10;
sum=sum + digit + num;
cout<<“\n”<<“sum of digits=“<<sum;
getch();
}
Program to compute sum of digits of a 4-digit number
Try the Following problems
1. Write a C++ program to read the price of an item in
decimal form(like 15.95) and print the output in
paise(like 1595 paise).
2. Write a C++ program to covert distance in mm to cm,
inch, feet (1 cm =10mm, 1inch=2.5cm, 1 feet =12
inches).
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What output is generated by following statements when executed one after another?
• cout<<“welcome\nto\nc++”;
• cout<<“How are you”;
• cout<<endl;
• int a =90;
• cout<<“a”;
What are the errors in following statements?
Void main()
{
Cout<<“Enter a”;
Cin>>a;
}
• void main()
• {
• a int;
• b char;
• a,b int
• }
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From www.classnotesmit.blogspot.com
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