LEARN WITH CLASSMATE: November 2015

Saturday 28 November 2015

TUTORIAL 2

USING TAGS

Include the following in the page

<!DOCTYPE html>

<html>

<body>

WELCOME TO MY PAGE

</body>

</html>

<!DOCTYPE html>

specifies the type of webpage is html

it instructs the web browser which version of html is being used, html indicates HTML5
if document type declaration is not specified, browser may behave in a peculiar way

<html> the opening tag, denotes the beginning of the html document

</html> the closing tag, denotes the end of html document

whatever is written between will be considered as html document

<body> denotes the beginig of the body of the html page

</body> denotes the end of the body

So whatever you have typed now within the <body> and </body>, is the body

WELCOME TO MY PAGE is the body here, and displayed in the browser window

</html> </body> - closes the respective elements

All the tag do not have the closing tags. there are certain tags which do not have the closing tags

Tags which do hold any contents will close themselves. So they do not need a separate closing tag

eg : <br> - denotes the line break

it doesnt wrap any content

this might also be written like <br/>

it is a self closing tag. that mean, closing by itself.

generally used in xhtml coding

xhtml is another version of html based on another markup lanuage xml

Any tag which has content must be closed

Syntax : opening tag -> content -> closing tag

This makes the code easier to understand

TUTORIAL 1

WHAT IS HTML?

HTML - Hyper Text Markup Language

It is the standard markup language used to create web pages.

A markup language is a set of markup tags

HTML documents are described by HTML tags

Each HTML tag describes different document content

It is used by most websites to create visually engaging webpages, user interfaces for web applications, and user interfaces for many mobile applications

HTML markup consists of several key components, including those called tags (and their attributes), character-based data types, character references and entity references.

We are here to learn HTML.

WHAT WE NEED TO START WITH HTML?

Notepad is a common text editor on Windows-based computers (usually found under the Programs > Accessories menu)

Mac OSX computers come bundled with TextEdit

But any program that lets you fiddle with text will do.

LETS BEGIN !

Type this in to your text editor:

My First HTML Page Welcome here

Now create a folder called “html” wherever you like to save files on your computer and save the file as “myfirstpage.html”.

It is important that the extension “.html” is specified
Some text editors, such as Notepad, will automatically save it as “.txt” otherwise.

You also need to ensure that your file is being saved as plain text.

Make sure you check the “Plain text” format option before creating a new file.

Open a web browser and type in the location of the file, you just saved (e.g : “C:\html\myfirstpage.html”), in the address bar and hit return.

Alternatively, go to the File menu of the browser, select Open, and browse for the file.

Here we have created a very simple webpage of our own. Its that easy....

You may be tempted to use a dedicated software program such as Adobe Dreamweaver.

You should be very careful when using these programs, especially if you are a beginner

Software programs such as these will never give you the same control over a web page as coding by hand.

If you do decide to use specialized code-editing software, we recommend one in which you are still coding by hand.

Saturday 14 November 2015

CONSTANTS

Constants in C refer to the fixed values that do not change during the execution of a program
There are basically 2 types of constants in C :

Primary Constants

Secondary Constants

In this lesson, we will learn only about the primary constants: Numeric and Character Constants

NUMERIC CONSTANTS

There are two types of Numeric Constants

Integer Constants

Real Constants

INTEGER CONSTANTS

An integer constant refers to a sequence of digits.There are 3 types of integers

Decimal : Consists of a set of digits 0 to 9

Octal : Consists of any combination of digits from 0 to 7 with a leading 0

Hexadecimal :

They may include alphabets A/a to F/f

These alphabets represent the numbers 10 to 15 respectively

Consists of the digits preceded by 0x or 0X

Other rules for construction Integer Constants :

It must not have a decimal point

It could be either positive or negative

If no sign precedes, it is assumed to be positive

Embedded spaces/ blanks, commas and non-numeric characters are not permitted

The allowable range for integer constants is -32768 to 32767 for 16 bit machines and -2 147 483 648 to 2 147 483 647 in 32 bit machines

It is also possible to store large integer constants on these machines by appending qualifiers such as U/u, L/l and UL/ul to the constants

REAL CONSTANTS

A real constant is often called a Floating Point Constant.

It could be written in two forms :

Fractional Form

Exponential Form

Rules for constructing Real Constants for Fractional Form

It must have at-least one digit (0-9)

It must have a decimal point

It could be either positive or negative, by default it is positive

Embedded spaces, commas are not allowed with in a real constant

Rules for constructing Real Constants for Exponential Form

This form is usually used if he value of the constant is either too small or too large

Here the real constant is represented in 2 parts

Mantissa - the part before 'e'

Exponent - the part following 'e'

The general syntax :

mantissa e exponent

Mantissa part and the exponential part should be separated by letter 'e'

Mantissa part could be either positive or negative, by default it is positive

Exponent must have at-least one digit which must be a positive or negative integer, by default it is positive

Blank is not allowed

Range of real constants expressed in Exponential Form is -3.4e38 to 3.4e38

CHARACTER CONSTANTS

There are 2 kinds of Character constants :

Single Character Constants :

contains a single character enclosed within a pair of single quote marks

e.g:

'5' 'X' ';' ' '

here '5' is character and different from number 5

String Constants :

It is a sequence of characters enclosed in double quotes
The characters may be letters, numbers, special characters and blank spaces

e.g:

"Hello" "1987" "&...!" "X"

here "X" is a string , different from character 'X'

IDENTIFIERS

In C, the names of variables, arrays, functions, labels and various user defined items are called identifiers.

The variables, arrays, functions, etc. can be identified by giving them meaningful names.

These names are called identifiers

RULES FOR IDENTIFIERS

The first character of an identifier must be an alphabet or an underscore
Identifiers must consist of only alphabets, digits or underscore
Special symbos are not allowed
Keywords should not be used as the identifiers
Identifier should be a single word, i.e., No blank space is allowed
Identifiers can be both uppercase and lowercase. C is case sensitive, i.e., uppercase letters are different from lowercase letters

e.g : ADD , AdD, add are different identifiers

Valid Identifiers

Invalid Identifiers

ADD

3add

Numerics not allowed in the beginning

Add

add+123

+ is not allowed

_add

for

it is a keyword

Student_Name

ABC XYZ

Blank not allowed

Name

Student%123

% Is not allowed

A312B

_Add*5Add

* is not allowed

Friday 13 November 2015

KEYWORDS

The keywords are reserved for specific meanings in C language

C has nearly 32 keyword

Keywords, combined with the formal C syntax, forms the C programming language

The variables should not be named with any of the keywords as the meanings cannot be changed

All the keywords are lower case letters

Keywords are also called as reserved words

All the keywords have pre-defined meanings

auto double int struct

break else long switch

case enum register typedef

char extern return union

const float short unsigned

continue for signed void

default goto sizeof volatile

do if static while

auto	double	int	struct
break	else	long	switch
case	enum	register	typedef
char	extern	return	union
const	float	short	unsigned
continue	for	signed	void
default	goto	sizeof	volatile
do	if	static	while

auto

auto is used to define a variable of storage class automatic.

Variables declared within function bodies are automatic by default.

They are recreated each time a function is executed.

Since, automatic variables are local to a function, automatic variables are also called local variables.

break and continue

The break statement is used to jump out of the innermost enclosing loop (while, do, for or switch statements) explicitly and pass control to next statement immediately following the loop.

In other hand, continue statement is used to skip certain statements inside the loop.

switch, case and default

The switch statement tests the value of a expression and test with the different "case" values.

We can use "default" value, if it doesn't matches any of "case" values.

char

The char keyword is used for indicating the variable is of the type character.

const

const makes the value of a pointer or a variable unmodifiable.

This value cannot be changed in program.

do and while

while and do are used for looping in C.

double and float

double and float are used for indicating floating type variables.

Keywords float and double represents single precision and double precision floating point data respectively.

if and else

if and else are used in decision making in C.

enum :

enum is used to define enumerated type data type.

Enumerated data type creates a set of constant of type int.

extern

Keyword extern is used for indicating the variable is external

It is declared outside every function and can be accessed by any function.

for

Keyword for is used for looping in C.

goto

Keyword goto is used for unconditional jump to a labeled statement inside that function.

int

int is used for indicating the variable is of type integer.

short, long, signed and unsigned :

short, long, signed and unsigned are type modifiers that alters the meaning of base data type to yield new type.

return

Keyword return terminates the execution of current function and returns the value to the calling function

sizeof

sizeof is used to find the number of bytes of an object.

register

Variable of storage class register are much faster than normal variables

static

static is used for indicating the variable is of storage class static.

The value of the static variables persists until the end of the program.

struct

struct is used in creating a structure which provide means to group different types of variable under one name for easier handling.

typedef

Keyword typedef is used to explicitly associate a type with an identifier.

union

Union is used in creating a union which provide means to group different types of variable under one name for easier handling.

void

void is used to indicate that a function takes no arguments or returns no value.

volatile

volatile is used to create a volatile object.

A volatile object can be modified in unspecified way by the hardware.

C TOKENS

One or more characters grouped together to form basic elements of C are known as C Tokens

The C Tokens include identifiers, constants, variables, keywords, operators, strings and some special symbols

C CHARACTER SET

The characters can be used to form words, numbers , statements and expressions

The characters in C are grouped into four categories :

Letters / Alphabets : used for naming variables (identifiers) and keywords
Digits : used for forming numerical constants and naming variables
Special Symbols : used as operators
White Spaces

One or more characters grouped together form basic elements of C known as tokens which are used for building declarations, statements and expressions etc.

UNIT 3 : INTRODUCTION

C is a general purpose language

Like any other high level languages, c has two distinct parts : Syntax and Semantics

Syntax of a C language specify character set, words, operators, statements, sentences and the rules

According to these syntax rules, valid C language program can be formulated

Semantics of C language assigns exact meaning of actions to be performed by these valid syntactic language

A program is a set of statements, which will be executed in a sequential form

These statement are formed using C character set, identifiers, variables, data types, constants, etc.

In this unit, we will learn about these basic elements which are used in the C language.

Tuesday 10 November 2015

PROGRAMMING STYLE

All statements should be written in lowercase letters

Uppercase letters are used only for symbolic constants

The programmer can write the statement anywhere between the two braces following the declaration part

The user can also write more than one statement in one line separating them with a semicolon

The opening and closing braces should be balanced, i.e., if opening braces are three, then closing braces should also be three

Use comments whenever necessary.

Comments increase the program readability and also help to understand the program logic

EXECUTING A C-PROGRAM

Creation of program

Program should be written in a C editor
After typing the program, save it with extension .c

Compilation & linking of a program

Source program should be compiled using a C compiler.
Compiler checks for the syntax errors.
Once all the errors are corrected, compiler converts the source program into its equivalent machine language code called as the Object Program or Object Code
The object program is required for execution by the computer
Linking is also essential process that puts all other program files and functions, that are required by the program, together
e.g:

If the program contains the built in function sqrt(), then the object code of this function should be linked to the main program from math.h library of the system

Executing the program

After the compilation and linking, the executable code will be loaded in the computer's main memory and the program is executed

Saturday 7 November 2015

BASIC STRUCTURE OF C PROGRAM 3

PROGRAM TO DEMONSTRATE ALL THE SECTIONS OF A C-PROGRAM

OUTPUT

BASIC STRUCTURE OF C PROGRAM 2

MAIN FUNCTION SECTION

All the C program contains one or more functions but, there must always be one main()

Execution of every C program begins from the function main()

This section contains 2 parts :

Declaration part - Declares all the variables used in the executable part.

Executable part

These two parts must be within the opening and closing braces ({ and })
Program execution starts from the opening brace and ends at the closing brace
All the statements in the declaration part & executable part must end with a semicolon

SUB - PROGRAM SECTION

This section contains the user defined functions.

These functions are invoked in the main function.

We can have any number of our own functions

These functions are generally placed after the main function, although they may appear in any order.

These functions are executed only when we invoke these functions

BASIC STRUCTURE OF C PROGRAM 1

The C program usually contain one or more sections.
To write a C program we first create a function main to accomplish a specific task
A function is a subroutine that contains the statements, enclosing them within { and } to perform the required task.
Except the function main(), rest of the sections are optional.
Different sections of a C-Program are shown below :

STRUCTURE OF C-PROGRAM

DOCUMENTATION SECTION

Contains comments such as : program description, programmer's name, date on which it is written and other details required by the program
A comment in a C program is ignored by the compiler
'/*' is used to mark the start of a comment and it terminate with '*/'
There must be no gap between the asterisk (*) and slash (/)
Comments are used to enhance program readability and understandability by giving the description or other detail about the program
Comments may be placed anywhere in the program, but are not allowed in the middle of any keyword or identifier

LINK SECTION

It helps to include the external file functions from the system library.

We must add an #include instruction in the program, which instructs the compiler to link the specified function in the library.

These library files are called as header files.

Header files can optionally be included in the program as per the requirement.

When we compile the C program,the header files are also compiled with the original program.

All the header files are included into the program by preprocessor directives.

Preprocessor directives are processed before a source program is handed over to the compiler.

these should be placed in a source program before the function main()

All the preprocessor directives should start with # and end without semicolon(;)