C++ rajan

C++
SUBMITTED BY-RAJANDEEP KAUR
ROLL NO- 115332
BRANCH- CSE (2nd SEM)

SUBMITTED TO- Er. JAGDEEP SINGH MALHI

1
The Task of Programming

► Programming a computer involves writing
instructions that enable a computer to carry
out a single task or a group of tasks
► A computer programming language requires
learning both vocabulary and syntax
► Programmers use many different programming
languages, including BASIC, Pascal, COBOL,
RPG, and C++
► The rules of any language make up its syntax
► Machine language is the language that
computers can understand; it consists of 1s
and 0s

1
The Task of Programming

►A translator (called either a compiler or an
interpreter) checks your program for syntax
errors
► A logical error occurs when you use a
statement that, although syntactically
correct, doesn’t do what you intended
► You run a program by issuing a command to
execute the program statements
► You test a program by using sample data to
determine whether the program results are
correct

1
Procedural Programming

► Procedural programs consist of a series of steps or
procedures that take place one after the other
► The programmer determines the exact conditions
under which a procedure takes place, how often it
takes place, and when the program stops
► Programmers write procedural programs in many
programming languages, such as COBOL, BASIC,
FORTRAN, and RPG
► You can also write procedural programs in C++

1
A main( ) Function in C++

► C++ programs consist of modules called
functions
► Every statement within every C++ program is
contained in a function
► Every function consists of two parts:
 A function header is the initial line of code in a C++
which always has three parts:
► Return type of the function
► Name of the function
► Types and names of any variables enclosed in
parentheses, and which the function receives
 A function body

1
Creating a main( ) Function

► Every complete C++ statement ends with a
semicolon
► Often several statements must be grouped
together, as when several statements must occur in
a loop
► In such a case, the statements have their own set
of opening and closing braces within the main
braces, forming a block

1
Working with Variables

► In C++, you must name and give a type to
variables (sometimes called identifiers) before
you can use them
► Names of C++ variables can include letters,
numbers, and underscores, but must begin
with a letter or underscore
► No spaces or other special characters are
allowed within a C++ variable name
► Every programming language contains a few
vocabulary words, or keywords, that you need
in order to use the language

1

► A C++ keyword cannot be used as a variable
name
► Each named variable must have a type
► C++ supports three simple types:
 Integer — Floating point — Character
► An integer is a whole number, either positive
or negative
► An integer value may be stored in an integer
variable declared with the keyword int
► You can also declare an integer variable using
short int and long int

1
► Explicitly stating the value of a variable is
called assignment, and is achieved with the
assignment operator =
► The variable finalScore is declared and
assigned a value at the same time
► Assigning a value to a variable upon creation is
often referred to as initializing the variable

1
Creating Comments

► A line comment begins with two slashes (//) and
continues to the end of the line on which it is
placed
► A block comment begins with a single slash and an
asterisk (/*) and ends with an asterisk and a slash
(*/); it might be contained on a single line or
continued across many lines

1 Using Libraries and
Preprocessor Directives
► Header files are files that contain predefined
values and routines, such as sqrt( )
► Their filenames usually end in .h
► In order for your C++ program to use these
predefined routines, you must include a
preprocessor directive, a statement that tells
the compiler what to do before compiling the
program
► In C++, all preprocessor directives begin with
a pound sign (#), which is also called an
octothorp
► The #include preprocessor directive tells the
compiler to include a file as part of the finished
product

2
C++ Binary Arithmetic Operators

► Often after data values are input, you perform
calculations with them
► C++ provides five simple arithmetic operators
for creating arithmetic expressions:
 addition (+) – subtraction (-)
 multiplication (*) – division (/)
 modulus (%)
► Each of these arithmetic operators is a binary
operator; each takes two operands, one on each
side of the operator, as in 12 + 9 or 16.2*1.5
► The results of an arithmetic operation can be
stored in memory

2
Shortcut Arithmetic Operators
► As you might expect, you can use two minus
signs (--) before or after a variable to
decrement it

2

► The prefix and postfix increment and decrement
operators are examples of unary operators
► Unary operators are those that require only one
operand, such as num in the expression ++num
► When an expression includes a prefix operator, the
mathematical operation takes place before the
expression is evaluated
► When an expression includes a postfix operator, the
mathematical operation takes place after the
expression is evaluated

2

► Thedifference between the results
produced by the prefix and postfix
operators can be subtle, but the
outcome of a program can vary greatly
depending on which increment
operator you use in an expression

2
Evaluating Boolean Expressions
► The unary operator ! Means not, and essentially reverses
the true/false value of an expression

2
Selection

► Computer programs seem smart because of
their ability to use selections or make decisions
► C++ lets you perform selections in a number of
ways:
 The if statement
 The switch statement
 The if operator
 Logical AND and Logical OR

2 Some Sample Selection
Statements within a C++ Program

2
The if Statement

► Any C++ expression can be evaluated as part of
an if statement

2
The switch Statement
► When you want to create different outcomes
depending on specific values of a variable, you can
use a series of ifs shown in the program statement in
Figure 2-14
► As an alternative to the long string of ifs shown in
Figure 2-14, you can use the switch statement
► The switch can contain any number of cases in any
order

2
The if Operator

► Another alternative to the if statement involves the if
operator (also called the conditional operator), which is
represented by a question mark (?)
► E.g.
► cout<<(driveAge<26)?”The driver is under 26”:”The
driver is at least 26”;
► The if operator provides a concise way to express two
alternatives
► The conditional operator is an example of a ternary
operator, one that takes three operands instead of just
one or two

2
Logical AND and Logical OR

► In some programming situations, two or more
conditions must be true to initiate an action
► Figure 2-16 works correctly using a nested if—
that is, one if statement within another if
statement
► If numVisits is not greater than 5, the
statement is finished—the second comparison
does not even take place
► Alternatively, a logical AND (&&) can be used,
as shown in Figure 2-17

2
Logical AND and Logical OR

2
Using the Logical OR

► In certain programming situations, only one of
two alternatives must be true for some action to
take place
► A logical OR (||) could also be used
► A logical OR is a compound boolean expression in
which either of two conditions must be true for
the entire expression to evaluate as true
► Table 2-4 shows how C++ evaluates any
expression that uses the || operator

2
The while Loop

► Loops provide a mechanism with which to
perform statements repeatedly and, just as
important, to stop that performance when
warranted
while (boolean expression)
statement;
► In C++, the while statement can be used to loop
► The variable count, shown in the program in
Figure 2-21, is often called a loop-control
variable, because it is the value of count that
controls whether the loop body continues to
execute

2
The for Statement

► The for statement represents an alternative to the while
statement
► It is most often used in a definite loop, or a loop that must
execute a definite number of times
► It takes the form:
for (initialize; evaluate; alter)
statement;

C++ rajan

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