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Lecture 5+6 Introduction to computer & programming. MS SADIA EJAZ CS DEPARTMENT. The Internet. It is a huge network of computers, which links many different types of computers all over the world.

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lecture 5 6 introduction to computer programming

Lecture 5+6 Introduction to computer & programming

MS SADIA EJAZ

CS DEPARTMENT

MS Sadia Ejaz CIIT ATTOCK

the internet
The Internet

It is a huge network of computers, which links many different types of computers all over the world.

It is a network of networks, which share a common mechanism for addressing (identifying) computers, and a common set of communication protocols for communication between two computers on the network.

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2

the internet s major services
The Internet’s Major Services

The World Wide Web

Electronic mail

News

File Transfer Protocol

Chat

Instant Messaging

Online- Services

Peer-to-Peer Services

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3

the world wide web
The World Wide Web

The World Wide Web (commonly shortened to the Web) is a system of interlinked hypertext documents accessed via the Internet.

With a Web browser, a user views Web pages that may contain text, images, videos, and other multimedia and navigates between them using hyperlinks.

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web search engine
Web Search Engine

A Web search engine is a search engine designed to search for information on the World Wide Web.

A search engine lets you search for information by typing one or more words. The engine then displays a list of Web pages that contain information related to your words.

Example: Google search engine

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5

e mail
E - Mail

Electronic mail, often abbreviated to e-mail, is a store-and-forward method of writing, sending, receiving and saving messages over electronic communication systems.

6

programming language generations
Programming Language Generations
  • Machine languages: first generation
  • Assembly languages: second generation
  • Higher-level languages: third generation (3GLs)

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fading third generation languages
Fading Third-Generation Languages
  • FORTRAN (FORmula TRANslator)
  • COBOL (COmmon Business Oriented Language)
  • BASIC (Beginner’s All-Purpose Symbolic Instruction Code)
  • Pascal

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thriving third generation languages
Thriving Third-Generation Languages
  • C
  • C++
  • Java
  • ActiveX

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fourth generation languages 4gls
Fourth-Generation Languages (4GLs)
  • Builds programs with a front end, which is an interface that hides much of the program from the user
  • Provides prototypes, which are samples of the finished programs

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examples of fourth generation languages
Examples of Fourth-Generation Languages
  • Visual Basic (VB)
  • VisualAge
  • Authoring environments

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fifth generation languages 5gls
Fifth-Generation Languages (5GLs)
  • Advanced authoring environments considered by some to be 5GLs

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world wide web development languages
World Wide Web Development Languages
  • HyperText Markup Language (HTML)
  • Extensible Markup Language (XML)
  • Wireless Markup Language (WML)
  • Dreamweaver
  • Flash
  • Director

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systems development life cycle for programming
Systems Development Life Cycle for Programming
  • Phase 1: Needs analysis
  • Phase 2: Program design
  • Phase 3: Development (also called coding)
  • Phase 4: Implementation
  • Phase 5: Maintenance

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why we do programming
Why We Do Programming ?
  • For solving problems
    • Computers are used as a tool to solve complex problems by developing computer programs that provide the solution of the problems.
    • Example:
      • Program : For adding 2 numbers, i.e 3 and 5
      • Solution: A computer program will be developed for their addition.

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problem solving techniques
Problem-Solving Techniques
  • Program
  • Algorithm
  • Pseudo Code
  • Flowchart , etc.

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program
Program
  • A set of instructions that tells a computer what to do is called program.
  • Computer programs are written in programming languages.
  • A person who develops a program is called programmer.

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algorithms
Algorithms
  • It is a step-by-step procedure to solve a problem.
  • Properties of Algorithm
    • The given problem should be broken down into simple and meaningful steps.
    • The steps should be numbered sequentially.
    • The steps should be descriptive and written in simple English.

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pseudo code pseudo language
Pseudo Code / Pseudo Language
  • Algorithms are written in a language, which is similar to simple English , which is known as pseudo language.
  • The purpose of using pseudo code is that it may be easier for humans to read than conventional programming languages.
  • No standard for pseudo code syntax exists, as a program in pseudo code is not an executable program.

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parts of program development
Parts of Program Development
  • Two main parts
    • Logic Design
    • Coding

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logic design
Logic Design
  • Logic of the program is designed by specifying different steps required and the sequence of these steps to solve the problem.

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coding
Coding
  • The algorithm is converted into a program.

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example
Example
  • Algorithm for calculating and displaying the sum of two numbers,
    • Input A, B
    • Total / Sum A + B
    • Display Total
    • Exit

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advantages of algorithms
Advantages of Algorithms
  • Reduced Complexity
  • Increased Flexibility
  • Ease of Understanding

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flowchart
Flowchart
  • It is combination of two words i.e. flow and chart.
  • Flowchart is a graphical representation of an algorithm.
    • Chart consists of different symbols to display information about any program.
    • Flow indicates the direction of processing that takes place in the program.
  • It is used to show all the steps of an algorithm in a sequence.

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flowchart contd
Flowchart (contd.)

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uses of logic flowchart
Uses of Logic Flowchart
  • It is used to represent an algorithm in simple graphical manner.
  • It is used to show the steps of an algorithm in an easy way.
  • It is used to understand the flow of the program.
  • It is used to improve the logic for solving a problem.
  • Programs can be reviewed and debugged easily.

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basic flowchart symbols
Basic Flowchart Symbols
  • Input/Output

Parallelogram symbol is used to represent an input or output step. Input statement is used to get input from the user. The output statement is used to display a message to the use or to display a value.

Input

Output

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basic flowchart symbols contd
Basic Flowchart Symbols (contd.)
  • Process

Rectangle symbol is used to represent a process step.

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basic flowchart symbols contd1
Basic Flowchart Symbols (contd.)
  • Selection

Diamond symbol is used to represent a selection step.

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basic flowchart symbols contd2
Basic Flowchart Symbols (contd.)
  • Start/End

Oval symbol is used to represent the start or end of the flowchart.

End

Start

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basic flowchart symbols contd3
Basic Flowchart Symbols (contd.)
  • ConnectorIndicates that the flow continues where a matching symbol (containing the same letter) has been placed.

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basic flowchart symbols contd4
Basic Flowchart Symbols (contd.)
  • Flow LineLines indicate the sequence of steps and the direction of flow.

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example1
Example

Start

Input A, B

Sum = A+B

Display Sum

End

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program development process
Program Development Process
  • A programmer has to go through the following stages to develop a computer program:
    • Defining and Analyzing the Problem.
    • Designing the Algorithm
    • Coding or Writing the Program
    • Test Execution
    • Debugging
    • Final Documentation

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integrated development environment ide
Integrated Development Environment (IDE)
  • Editor
  • Compilers
  • Debugger
  • Linkers
  • Loaders

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slide38
Program is created in the editor and stored on disk.

Disk

Preprocessor program

processes the code.

Disk

Compiler creates object code and storesit on disk.

Disk

Compiler

Linker links the object

code with the libraries

Disk

Primary Memory

Loader

Loader puts program in memory.

Disk

Primary Memory

CPU takes each

instruction and executes it, possibly storing new data values as the program executes.

CPU

Preprocessor

Linker

Editor

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tools of the trade
Tools of the trade
  • Editor
    • First of all we need a tool for writing the code of a program. For this purpose we used Editors in which we write our code.

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debugger
Debugger

It is used to debug the program.

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linker
Linker

Most of the time our program is using different routines and functions that are located in different files, hence it needs the executable code of those routines/functions.

Linker is a tool which performs this job, it checks our program and includes all those routines or functions which we are using in our program to make a standalone executable code and this process is called Linking.

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loader
Loader

Another process which is needed to load the program into memory and then instruct the processor to start the execution of the program from the first instruction (the starting point of every C program is from the main function).

This processor is known as loader.

Linker and loaders are the part of development environment. These are part of system software.

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debugging in turbo c
Debugging in Turbo C++

An error in a computer program is known as bug.

The process of finding and removing bugs is known as debugging.

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types of errors
Types of Errors

Syntax Errors

Logical Errors

Run-Time Errors

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syntax errors
Syntax Errors

It is a type of error that occurs when an invalid statement is written in program.

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logical errors
Logical Errors

It is a type of error that occurs due to poor logic of the programmer.

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run time errors
Run-Time Errors

It is a type of error that occurs during the execution of program.

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c statement
C++ Statement
  • The statement of the program are writen under the main() function between the curely bracket{}.
  • These statement are the body of program
  • Each statement of the c++ ends with a semicolon(;)
  • C++ is a case sensitive language
  • The c++ statement are normally written in lowercase letters but in some exceptional but in some exceptional cases, these can also be written in upper case

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keyword
keyword
  • The words that are used by the language for special purpose are called keywords
  • e.g. in c++ program, the word main is used to indicate the starting of program, include is used to header files, int to declare an integer data type
  • All these words are keyword of c++
  • The keyword cannot be used as variable names in program

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identifiers
Identifiers

The identifiers are the names used to represent variable, constants, types, functions and labels in the program.

An identifier in C++ may consist of 31 characters.

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types of identifiers
Types of Identifiers
  • Standard Identifiers
    • A type of identifier that has special meaning in C++ is known standard identifier.
    • For example. cout, cin, etc.
  • User-defined Identifiers
    • The type of identifier that is defined by the programmer to access memory location is known as user-defined identifier.
    • For example, marks, age, etc.

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keywords
Keywords

Keyword is a word in C++ language that has a predefined meaning and purpose.

They are also known as reserved words.

The total number of keywords is 63.

For example, int, class, etc.

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data types
Data Types

The data type defines a set of values and a set of operations on these values.

A C++ program may need to process different types of data.

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data types1
Data Types

Data Type Purpose

int to store numeric values

float to store real values

double to store large real values

char to store character values

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integer data type
Integer Data Type

Integer data is numeric value with no decimal point or fraction.

Types of Integers Size in Bytes

int 2

short int 2

long int 4

unsigned int 2

unsigned long int 4

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real data types
Real Data Types

Real data is numeric value with decimal point or fraction.

It is also called floating point number.

Types of Real Size in Bytes

float 4

double 8

long double 10

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character data type
Character Data Type

char data type is used to store character value.

It takes 1 byte in memory.

The characters are stored in ASCII code form.

ASCII  American Standard Code for Information Interchange.

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integer overflow and underflow
Integer Overflow and Underflow
  • Integer Overflow
    • It occurs when the value assigned to an integer variable is more than maximum possible value.
  • Integer Underflow
    • It occurs when the value assigned to an integer variable is less than possible minimum value.

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variables
Variables

A variable is a named memory location or memory cell.

The value stored in a variable is referred by variable name.

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variables declaration
Variables Declaration
  • The process of specifying the variable name and its type is called variable declaration.
  • Syntax
    • Data type variable_name ;
    • e.g. int marks ;

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rules for declaring variables
Rules for Declaring Variables

Variable may include letter, numbers and underscore (_).

The first character of variable must be a letter or underscore _. The use of underscore is not recommended. The variables 9minute, #home and 2kg are invalid.

Blank spaces are not allowed in variable names. The variables my var and your car are invalid.

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rules for declaring variables contd
Rules for Declaring Variables (contd.)

Both upper and lower cases are allowed. A user-defined variable is conventionally written in lower case. The constants are conventionally written in upper case.

Special symbols cannot be used as variable name.

Reserved word cannot be used as variable name. The names int, void and while are invalid variables.

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rules for declaring variables contd1
Rules for Declaring Variables (contd.)

A variable can be up to 31 characters long for many compiler. If a variable consists of more than 31 characters, only first 31 characters will be used. The remaining characters will be ignored.

A variable can be declared only for one data type.

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variable initialization
Variable Initialization
  • The process of assigning a value to a variable at the time of declaration is known as variable initialization.
  • Syntax
    • Data type variable _name = value ;
    • e.g. int n = 100 ;
    • int n= 100 ;

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tokens
Tokens
  • A program statement consist of variable names, keywords, constant, operator etc, these elements of statement are called tokens

e.g.

int main(){int x,y;x = 5;

}

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example2
Example
  • simple program
  • #include< stdio.h >#include< iostream.h >int main(){int x;x = 5; cout << x; return 0;}

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