Introduction To Programming subject1.ppt

Introduction to Programming
Lecture # 1

Computer Program
• A computer program (software, or just a program) is a sequence of
instructions written to perform a specified task with a computer.
• A computer requires programs to function, typically executing the
program's instructions in a central processor.
• The program has an executable form that the computer can use directly to
execute the instructions. The same program in its human-readable source
code form, from which executable programs are derived (e.g., compiled)
• Computer source code is often written by computer programmers in
programming languages(C, C++, java)
• Source code may be converted into an executable file (sometimes called
an executable program or a binary) by a compiler and later executed by a
central processing unit.
• Alternatively, computer programs may be executed with the aid of an
interpreter, or may be embedded directly into hardware.

What is a Programming Language?
A vocabulary and set of
grammatical rules for instructing a
computer to perform specific tasks

Compiler
• Compiler is a computer program (or set of programs) that
transforms source code written in a programming language (the
source language) into another computer language (the target
language, often having a binary form known as object code).
• The name "compiler" is primarily used for programs that translate
source code from a high-level programming language to a lower
level language (e.g., assembly language or machine code).

Introduction to C++
• Most widely used programming language in existence
• Used in professional applications development because of its
immense flexibility and power
• Combines the facility for efficient procedural programming that it
inherits from C, with a powerful object-oriented programming
features
• Provides extensive facilities in its standard Library

What is an algorithm?
• In computer programming terms, an algorithm is a set of
well-defined instructions to solve a particular problem. It
takes a set of input(s) and produces the desired output.

Quality of Good Algorithm
• Input and output should be defined precisely.
• Each step in the algorithm should be clear and
unambiguous.
• Algorithms should be most effective among many different ways to
solve a problem.
• An algorithm shouldn't include computer code. Instead, the algorithm
should be written in such a way that it can be used in different
programming languages.

Example
• Write an algorithm to add two number.

Solution
Step 1: Start
Step 2: Declare variables num1, num2 and sum.
Step 3: Read values num1 and num2.
Step 4: Add num1 and num2 and assign the result to sum.
sum←num1+num2
Step 5: Display sum
Step 6: Stop

Flowchart
A flowchart is a diagrammatic representation of an algorithm. A
flowchart can be helpful for both writing programs and
explaining the program to others.

Example 2
Write an algorithm and draw a flowchart that will read the two
sides of a rectangle and calculate its area.

Solution
Step 1 start
Step2 : Declare a variable length and width
Step3: Reads the value of length and width
Step4: Calculate Area to multiply length and width;
Step5: Print A
Step 6:Stop

Example 3
Algorithm 2: Find the largest number among three numbers

Algorithm
Algorithm 2: Find the largest number among three numbers

Alogrithm
1. Start
2. Ask the user enter three integers a,b,c
3. Read the three values a,b,c
4. Check if a is greater than b
5. If true, then check a is greater than c
1. if true, then print ‘a’ as the greatest number
2. if false ,then print ‘c’ as the greatest number
6. If false, then check if b is greater than c
1. if true then print ‘b’ as the greatest number
2. if false, then print ‘C’ as the greatest number
7. Stop

Pseudocode
Pseudocode is an informal way of programming description
that does not require any strict programming language syntax
or underlying technology considerations. It is used for creating
an outline or a rough draft of a program. Pseudocode
summarizes a program’s flow, but excludes underlying details.
System designers write pseudocode to ensure that
programmers understand a software project's requirements
and align code accordingly.

Example
.Area of rectangle()
Begin
Read: Width & Length
Area=Width * Length
Print area
End

Example
Procedure: FindLargestNumber(a,b,c)
Begin
Read : a,b,c //(input)
If (a>b)
if (a>c)
Return a
Else
End

A Simple C++ Program
#include <iostream>
using namespace std;
int main( )
{
cout<<“Assalam-o-Alaikum";
return 0;
}//end of the main
<< is called insertion operator
>> is called extraction operator
Preprocessor Directive
Using Directive

Directives
1. Preprocessor Directive
- looks like a program statement but it’s not
- It is an instruction to the compiler
- A part of the compiler called preprocessor deals with these
directives before it begins the real compilation process
- The preprocessor directive #include tells the compiler to
insert another file into your source file (it inserts code of file
named after it as it is part of the source file)
2. Using Directive
- A C++ program can be divided into different namespaces
- A namespace is a part of the program in which certain names
are recognized

Keywords
• Reserved words in C++ are called keywords, have
special significance within the language
• Words “return” and “namespace” discussed in previous
example are examples of keywords
• Names for different entities that we use in our program
must not be same as any of the keywords in C++

Statements and Statement Blocks
• A statement is an instruction to the computer to do something. e.g.
adding two numbers or printing a string to the screen.
• Statements are the basic units for specifying
– What a program is to do, and
– The data elements it acts upon
• Most C++ statements end with a semicolon (;)
• Several statements can be enclosed between a pair of curly braces {} –
referred to as a statement block

Characters and Character Sets
• In your C++ programs you can use:
– Upper case letters ( A to Z )
– Lower case letters ( a to z )
– Space character
– Control characters ( new line, horizontal and vertical
tab)
– Special characters ( - [ ] {} () ~! # $%^&*+| /.,<>:;’” )

Escape Sequences
• When using characters in the program certain characters
can be problematic
• Like you cannot use a “tab” or a “new line” directly as
characters
• You can enter control characters as constants by means
of an escape sequence
• For example:
– n for new line, t for horizontal tab
– for backslash, ” for double quote

Escape Sequences
• An escape sequence is a sequence of characters that does not
represent itself when used inside a character or string literal, but is
translated into another character or a sequence of characters that
may be difficult or impossible to represent directly.

• The output we get is determined by what’s between
the outer double quotes in the statement
• cout<<“Assalam-o-Alaikum";
• A string of characters between a pair of double
quotes is called a string literal
• Double quote characters just identify the beginning
and end of the string literal and not part of the string
Escape Sequences

Documenting the Programs
• Documentation of programs is extremely important -- it can be done
using comments
• Two ways to comment our programs
– Single-line comment
– Multi-line comment (Block comment)
• Example,
//You must not nest multi-line comments
/*This starts an outer comment
/*This starts an inner comment, but the start will not be recognized
because of the outer comment.
Instead, the end of the inner comment will be interpreted as the end
of the outer comment.*/
This will cause the compiler to try to compile this part of the outer
comment as C++ code. */

Sample Program
• Documentation of programs is extremely important -- it can be done
using comments
• Two ways to comment our programs
– Single-line comment
– Multi-line comment (Block comment)
• Example,
//You must not nest multi-line comments
/*This starts an outer comment
/*This starts an inner comment, but the start will not be recognized
because of the outer comment.
Instead, the end of the inner comment will be interpreted as the end
of the outer comment.*/
This will cause the compiler to try to compile this part of the outer
comment as C++ code. */

The Standard Library
• The standard library contains substantial amount of
functions and other functionality that support the basic
capabilities of C++
• To use C++ effectively, you should make sure that you
have a good familiarity with the contents of the standard
library
• The definitions and declarations necessary to use
standard library facilities appear in the standard header
files
• Everything in the C++ standard library is defined within
the namespace std.

Summary
• A program in C++ consists of at least one function, which is called
main()
• The executable part of a function is made up of statements
contained between a pair of braces {}
• Basic unit for specifying what our program is to do and the data
elements is called statement
• A pair of braces {----} defines a statement block
• In C++, a statement is terminated by a semicolon (;)
• Keywords are a set of reserve words that have specific meanings in
C++. No entity in our program can have a name similar to a
keyword
• The code containing functions is usually stored in files with the
extension .cpp

Introduction To Programming subject1.ppt

More Related Content

Similar to Introduction To Programming subject1.ppt (20)

Recently uploaded (20)

Introduction To Programming subject1.ppt

Editor's Notes