Transcript Slide 1

Programming Fundamental
Instructor Name:
Lecture-2
Today’s Lecture
 What is Programming?
 First C++ Program
 Programming Errors
 Variables in C++
 Primitive Data Types in C++
 Operators in C++
 Operators Precedence
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What is Programming?
 Computer programming (often shortened to programming) is a process that
leads from an original formulation of a computing problem to executable
computer programs.
 Programming involves activities:
 Analysis
 Develop understanding
 Generating algorithms
 Verification of requirements of algorithms including their correctness and
resources consumption, and
 Implementation of algorithms in a target programming language (C++ in
our case)
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First Program in C++
using namespace std;
#include <conio.h>
#include <iostream>
main()
{
cout<<" Welcome to GC University";
getch();
}
→# is HASH and also called SHARP
→#include: This is a pre-processor directive. It is not part of our program; it is
an instruction to the compiler. It tells the C compiler to include the
contents of a file i.e. iostream. The compiler knows that it is a
system file, and therefore looks for it in a special place.
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First Program in C++
Namespace in C++
 Different libraries may have functions or variables with same name
 A namespace is designed to overcome this difficulty by using additional
information to differentiate similar functions, classes, variables etc. with
the same name available in different libraries.
 Using namespace, you can define the context in which names are defined.
 In essence, a namespace defines a scope.
 A namespace definition begins with the keyword namespace followed by
the namespace name as follows:
namespace namespace_name;
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First Program in C++
The Using Directive
 To call the namespace-enabled version of either function or variable,
prepend the namespace name as follows:
name_space::code;
 You can also avoid prepending of namespaces with the using namespace
directive which tells the compiler that the subsequent code is making use
of names in the specified namespace
 The using directive can also be used to refer to a particular item within a
namespace. For example,
using std::cout;
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First Program in C++
#include directive
 Both user and system header files are included using the preprocessing
directive ‘#include’.
 It has two variants:
 #include <file> - used for system header files. It searches for a file
named file in a standard list of system directories.
 #include "file“ - used for header files of your own program. It
searches for a file named file first in the directory containing the
current file, then in the quote directories and then the same directories
used for <file>.
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First Program in C++
main() Function
 All C++ Must have main() function
 When the operating system runs a program in C, it passes control of the
computer over to that program.
 The main() function uses its parentheses() to contain any information
typed after the program name at the command prompt. This is useful for
more advanced programming.
 The curly braces {} are used for organization. They contain programming
instructions that belong to the function. Those programming instructions
are how the function carries out its task or does its thing.
 Without main() function a C++ program will not execute.
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First Program in C++
cout in C++
 The predefined object cout is an instance of ostream class.
 The cout object is said to be "connected to" the standard output device,
which usually is the display screen.
 The cout is used in conjunction with the stream insertion operator, which
is written as << which are two less than signs indicates the direction of
data
cout<<" Welcome to GC University";
 Thing between the double quotes (“ ”) is known as character string, will
display it on the screen.
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First Program in C++
Semicolon “;” in C++
 The semicolon is part of the syntax of C++.
 It tells the compiler that you're at the end of a command.
 The semicolon (;) will be used at the end of the every statement other wise
compiler will report an error.
 The error reported as result of missing semicolon(;) is referred as syntax
error
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Programming Errors
Three Types of Errors
1) Syntax Error
Detected By the Compiler
2) Logical Error
Produce incorrect result due to wrong logic
3) Runtime Error
Causes the program to abort
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Variables in C++
What is Variable?
 A variable is used to store a piece of data for processing.
 It is called variable because you can change the stored value with new
value during program execution
 A variable is a named storage location, that stores a value of a particular
data type
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Variables in C++
Variable
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Variables in C++
Dissecting a Variable
 In a Program a variable Consists of:
 Name: Used as identifier for the variable. e.g. radius, area, age
 Type: Represents the type of data a variable will hold. e.g. Integer,
Float
 Size: Represents memory size a variable require to store a value. It
depends on the type of variable and compiler that compiles the code.
 Value: Actual value that is stored in variable
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Variables in C++
Variable Declaration Rule
 A variable must start with:
 Character
 Underscore _ (Not recommended)
 A variable must [recommended]
 Consists of sequence of Upper/lower case Characters, numbers (0-9), _
up to certain length
 have a name that is self-descriptive and closely reflects the meaning of
the variable e.g. age, user_name, email, address,ph_no
 not be of single character and meaning less unless they are common
names like x ,and z for coordinators
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Variables in C++
Variable Declaration Rule
 It is perfectly okay to use long names of says 30 characters to make sure
that the name accurately reflects its meaning!
 Use singular and plural nouns prudently to differentiate between singular
and plural variables. For example, you may use the variable row to refer to
a single row number and the variable rows to refer to many rows.
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Variables in C++
Variable Declaration Rule
Prohibition:
 White space (blank, tab, new-line) and other special characters (such as +, , *, /, @, &, commas, etc.) are not allowed.
 It cannot begin with a digit.
 An identifier cannot be a reserved keyword or a reserved literal (e.g. int,
double, if, else, for, main,while,break).
 Identifiers are case-sensitive. E.g. A rose is NOT a Rose, and is NOT
a ROSE.
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Variable Data Types
Data Types
 While doing programming in any programming language, you need to use
various variables to store various information.
 Variables are nothing but reserved memory locations to store values, this
means variable reserve some space in memory.
 Information store in variables may be of various data types like character,
wide character, integer, floating point, double floating point, boolean etc.
 Based on the data type of a variable, the operating system allocates
memory and decides what can be stored in the reserved memory.
 A data type is set of values and operations performed on those value
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Variable Data Types
Primitive Data Types

Integers: used to store numerical values(signed or unsigned).

Characters: used to store Characters ‘A’ to ‘z’. Every alphanumeric digit
and or symbol encoded in single quotes in considered a character.

Floating-point: used store the decimal point numbers.

Boolean: A special type called bool , which takes a value of
either true or false.
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Variable Data Types
Sizeof Operator
 The sizeof is a keyword, but it is a compile-time operator that determines
the size, in bytes, of a variable or data type.
 The sizeof operator can be used to get the size of classes, structures, unions
and any other user defined data type.
 The syntax of using sizeof is as follows:
sizeof (data type)
 Where data type is the desired data type including classes, structures,
unions and any other user defined data type.
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Variable Data Types
Sizeof Operator Example
#include <iostream>
using namespace std;
int main() {
cout << "Size of char : " << sizeof(char) << endl;
cout << "Size of int : " << sizeof(int) << endl;
cout << "Size of float : " << sizeof(float) << endl;
cout << "Size of double : " << sizeof(double) << endl; return 0;
}
OUTPUT
Size of char : 1
Size of int : 4
Size of float : 4
Size of double : 8
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Primitive Data Types
typedef Declaration
 You can create a new name for an existing type using typedef. Syntax to
define a new type using typedef is:
typedef type newname;
 The following tells the compiler that feet is another name for int:
typedef int feet;
Now, the following declaration is perfectly legal and creates an integer
variable called distance:
feet distance;
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Primitive Data Types
Character Data Type
 The data type char is the smallest integral data type with range (128 to 127)
 char data type can represent every key on your keyboard.
 Enclosed in single quotation marks. e.g. 'A', 'a', '0', '*', '+', '$', '&', ‘ ‘
 Several character set are in use.
 American Standard Code for Information Interchange (ASCII),
 Extended Binary- Coded Decimal Interchange Code (EBCDIC).
 The ASCII character set has 128 values.
 65 represents 'A', and the value 43 represents '+'.
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Operators in C++
What is an operator?
 An operator is a symbol that tells the compiler to perform specific
mathematical or logical manipulations.
 C++ is rich in built-in operators and provides the following types of
operators:
 Arithmetic Operators
 Relational Operators
 Logical Operators
 Bitwise Operators
 Assignment Operators
 Misc Operators
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Operators in C++
Arithmetic Operator
 Following are arithmetic operators available in C++
 Assume variable A holds 10 and variable B holds 20, then:
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Operators in C++
Relational Operator
 Relational operators are used to compare two values or expressions to
evaluate the relationship.
 Comparing floating point values using any of the relational operators is
dangerous. This is because small rounding errors in the floating point
operands may cause an unexpected result.
 A relationa operator comparison will always return one of the two possible
values either true or false.
 For the example on next slide assume variable A holds 10 and variable B
holds 20, then:
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Operators in C++
Relational Operator
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Operators in C++
Logical Operator
 The logical operators, logical AND (&&) and logical OR (||), are used to
combine multiple conditions formed using relational or equality
expressions
 The operator && corresponds to the Boolean logical operation AND,
which yields true if both its operands are true, and false otherwise.
 The operator || corresponds to the Boolean logical operation OR, which
yields true if either of its operands is true, thus being false only when both
operands are false.
 The Logical Operator, logical NOT (!) has only one operand, to its right,
and inverts it, producing false if its operand is true, and true if its operand
is false.
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Operators in C++
Bitwise Operator
 Bitwise operator works on bits and perform bit-by-bit operation. The truth
tables for &, |, and ^ are as follows:
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Operators in C++
Assignment Operator
 An assignment operator is the operator used to assign a new value to a
variable
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Assignment Rules
Assignment Rules
 assigns a literal value (of the RHS) to a variable (of the LHS)
 evaluates an expression (of the RHS) and assign the resultant value to a
variable (of the LHS).
 The RHS shall be a value; and the LHS shall be a variable (or memory
address).
 Some Valid and Invalid Assignments
X+ 3 = y + 4
Wrong
x +4 = Z
Wrong
2=x
Wrong
Z = x +4
Correct
x=y
Correct
x=2
Correct
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Assignment Example
using namespace std;
#include <iostream.h>
main ( )
{
int x ;
int y ;
int z ;
x = 10 ;
y = 20 ;
z=x+y;
cout << " x = " << x ;
cout << " y = " << y ;
}
cout << " z =x + y = " << z ;
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Operator Precedence
What is Precedence
 In mathematics and computer programming, the order of operations
(sometimes called operator precedence) is a rule used to clarify which
procedures should be performed first in a given mathematical expression.
Highest: ( )
Next:
*,/,%
Lowest: + , -
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