This document summarizes the basics of the C programming language as presented by Karthik Srini. It defines the key tokens in C like keywords, identifiers, literals, punctuators, and operators. It describes the different types of literals, variables naming rules, and provides examples. The document also outlines the rules for writing C programs including declaring main function, data types, comments and braces. It concludes with a simple sample C program to print "Hello World".

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Fundamentals of Computing And C Programming
Unit - II - Basics of C Language

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Basics of C Language
Tokens | Rules | Sample Programs

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Tokens
Tokens are the smallest individual units of a program. Different type of tokens are :
1. Keywords
2. Identifiers
3. Literals (or) Constants
4. Punctuators
5. Operators

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Keywords
Keywords are the words that convey a special meaning to the
language compiler. They are reserved words.
For example,
void , main , int , double , float , for , while , etc…

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Identifiers
Identifiers are the fundamental building blocks of a program and are
used in names given to different parts of a program.
For Example,
int number = 10 ; where number is an identifier.
int add ( int a, int b ) where add is an identifier.

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Rules for variable declaration in C
• Characters Allowed :
Underscore ( _ )
Capital Letters ( A – Z )
Small Letters ( a – z )
Digits ( 0 – 9 )
• Blanks & Commas are not allowed.
• No Special Symbols other than underscore ( _ ) are allowed.
• First Character should be alphabet or Underscore.
• Variable name Should not be a Reserved Word (or) Keyword

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Allowed Declarations :
_num=10;
num=10;
num1=10;
num_1=10;

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Declarations that are not allowed Reason
num 1=10; White space between num and 1
23num=10; Declarations can not begin with a number
@num=10;
No other special characters except Underscore
( _ ) are allowed

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Literals
Literals are the data items that have fixed data values. They are also known as
constants. The types of literals are :
1. Integer Literal
2. Floating Point Literal
3. Character Literal
4. String literal
5. Boolean Literal
6. Null Literal

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Integer Literal
An integer literal can be a decimal, octal, or hexadecimal constant. A
prefix specifies the base or radix: 0x or 0X for hexadecimal, 0 for octal,
and nothing for decimal.

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Rules for constructing integer constant

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Floating Point Literal
A floating-point literal has an integer part, a decimal point, a fractional
part, and an exponent part. You can represent floating point literals
either in decimal form or exponential form.
While representing using decimal form, you must include the decimal
point, the exponent, or both and while representing using exponential
form, you must include the integer part, the fractional part, or both.
The signed exponent is introduced by e or E.

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Few Examples,
3.14159 /* Legal */
314159E-5L /* Legal */
510E /* Illegal: incomplete exponent */
210f /* Illegal: no decimal or exponent */
.e55 /* Illegal: missing integer or fraction */

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Rules for constructing floating point literal

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Illustrative Examples for representation by
exponents

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Character Literal
Any character enclosed within single quotes is called a character
literal.
For example,
char alphabet = ‘ a ’ ;
char num = ‘ 1 ’ ;

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String Literal
When two or more number of characters are enclosed within double
quotes, it is called a string literal.
For example,
char subject = “ Computer Applications ” ;

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Boolean Literal
A boolean literal can take only two values as constant, they are 0 or 1
(i.e.) True or false.
For Example,
boolean flag = 1 ;
boolean is a datatype in Java programming language

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Null Literal
Null literal is normally used to terminate strings.
For example,
‘ 0 ’

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Punctuators
The different punctuations used in the source code of the program are
called Punctuators.
For example,
1. Comma ( , )
2. Semicolon ( ; )
3. Braces - ( ) , { } , [ ] , < >
4. Other Special characters - @ , # , * , & , % , etc…

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Operators
Operators are special symbols that perform specific operations on
one, two, or three operands, and then return a result. They are
classified as :
1. Unary operators - act on only one operand.
2. Binary operators - act on two operands.
3. Ternary operators - act on three operands.

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Unary Operators
Unary operators act only upon one operand.

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Increment : ++x, x++
Decrement : −−x, x−−
Address : &x
Indirection : *x
Positive : +x
Negative : −x
One's complement : ~x
Logical negation : !x
Sizeof : sizeof x, sizeof(type-name)
Cast : (type-name) cast-expression

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Binary Operators
Binary operators are the operators that act upon two operands at the
same time.
For example,
Arithmetic operators : + , - , / , %, * , etc…
Logical operators : &&, ! , || , etc…

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Ternary Operator
Ternary operator is that which acts upon three operands, they are also
known as conditional operator. ( ? : )
Example,
( num > 10 ) ? max : min ;

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Rules for writing a C Program
• Every C Program Should have exactly one main function
• C Program Execution Always Starts from main.
• Execution of C Program begins at Opening brace of function and
ends at closing brace of the function
• Generally all statements in c are written in Lowercase Letters.
• Uppercase Letters are used for Symbolic names, output strings and
messages
• Every C statement must ends with semicolon.

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Rules for writing a C Program
•All variables must be declared with respective data types
before using .
•C is free form-Language
•Comments can be inserted anywhere in C Program , but
nested comments are not supported by C .
•Braces are Generally Used for the Grouping of statements

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Sample Program
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
printf(“ Hello world ");
getch();
}
Hello World