Tokens are the basic building blocks that make up statements in a programming language. There are different types of tokens such as keywords, identifiers, constants, punctuators, and operators. Keywords are predefined words that have special meaning, identifiers are user-defined names for variables and functions, constants cannot change value during program execution, punctuators are symbols that separate tokens, and operators perform operations on operands. The main() function is called by the operating system to start a program and contains the main body of code. Input and output functions allow a program to accept user input and display output. Loops execute a block of code multiple times based on a loop condition.

1. Compiler
Construction
Rahila Farooq

2. Muhammad Bilal
BCS19-217
Presentation Topic
Tokens
Keywords
Identifier

3. Token:
Keywords Identifier
Constants Punctuators
Operators
A token is language elements that used to form a statement may consist
of different types of tokens.
Different types of token:

4. Keywords:
Keywords is a word in language that has a predefined meaning and purpose.
Examples:
digit decimal text final
fixed pass fail self
catch key nil again
test then free loop
typeof auto lambda import

5. Identifier:
Identifier is the name of a variable or function-name etc. this is also called
user-defined words.
Rules of Identifier declerations:
I. Identifier may include letters, numbers and $ (the Dollar symbol)
II. A variable starts with the $ sign, followed by the name of the variable.
III. Both upper and lowers cases allowed
IV. Keywords cannot be used as identifier name.
V. Variable names are case-sensitive ($age and $AGE are two different
variables)

6. Constants
integers floating characters Boolean
Constant is a quantity that cannot be changed during execution of a
program.
Operators
Operator is a symbol that perform some operation. It acts on different
openrands .There are types of operators like arithmetic, logical, conditional,
relational, bitwise, assignment operators etc.
Arithmetic Operators
+ - * / %

7. Logical Operators
&&(AND) ||(OR) !(NOT)
Relational Operators
< <= > >= == !=
Bitwise Operators
& | << >> ~ ^
Assignment Operators
= += /= %=

8. White Spaces:
Punctuators is a symbol that is used to seperate two tokens.
{ } [ ] ( ) , ; . :
Punctuators (Seperators)
The white spaces used in programs to increase readability. Dieffernt type of
White spaces used .Compiler ignore extra white spaces.
● Space
● Tab

9. Data Types:
Defines a set of values. Basic data types such as int, float, char etc
In C Alternate Purpose
int digit An digit variable is used to
store an integer
float decimal Decimal is used to store
decimal numbers
char text Text is used to store
characters and letters

10. Data Types:
Defines a set of values. Basic data types such as int, float, char etc
In C Alternate Purpose
int digit An digit variable is used to
store an integer
float decimal Decimal is used to store
decimal numbers
char text Text is used to store
characters and letters

11. Variable declaration &
initialization:
Basic Structure :
Variable declaration: data_type $variable_name(statement
terminator)
Variable initialization: data_type $variable_name = value(statement
terminator)
Example:
The forward slash (or
simply slash) character (/)
is used as a statement
terminator.
Variable declaration: digit $num/
Variable initialization: digit $num = 10/

12. Romail Bhatti
BCS19-226
Presentation Topic
Comments
Loop

13. Comments:
In programming, comments are hints that a programmer can add to make
their code easier to read and understand. For example,
In C
// - Single Line Comment.
/*... */ - Multi-line Comment.
Alternate
# - Single Line Comment.
#* *# - Multi-line Comment.

14. Loop:
loop Executes a sequence of statements multiple times that manage by loop
variable.
In C
for(initialisation ; Condition ; inc/dec )
{
// for loop body
}
Alternate
loop(initialisation / Condition / inc/dec
)
{
# for loop body
/}

15. Examples
➔
loop ( digit $counter=0 / $counter < 9 / $counter++ )
{
# Statement
/}

16. Lexeme Token Lexeme Token
loop keyword $counter Identifier
( Punctuator < Relational Operator
$counter Identifier 9 constant
digit Keyword(for Integer) / Punctuator
= Assignment Operator $counter Identifier
0 Constant ++ Uniary Operator
/ Punctuator ( Punctuator
$counter Identifier /} Punctuator

17. Musa Khan
BCS19-247
Presentation Topic
Input / Output

18. Output:
When we say Output, it means to display some data on screen programming
provides a set of built-in functions to output the data on the computer
screen.
In C
printf(“OUTPUT”);
Alternate
echo “ OUTPUT”/

19. Lexeme Token
echo keyword
“OUTPUT” text
/ Punctuator
echo “OUTPUT”/

20. Input:
When we say Input, it means to feed some data into a program. An input can
be given in the from the command line. Programming provides a set of built-
in functions to read the given input and feed it to the program.
In C
scanf(“%d”, &counter);
Alternate
read($counter)/

21. Lexeme Token
read keyword
( Punctuator
$counter identifier
) Punctuator
/ Punctuator(terminator)
read($counter)/

22. Muhammad Ali
BCS19-244
Presentation Topic
Main Body

23. Main Body:
An operating system always calls the main() function when a programmers or
users execute their programming code. It is responsible for starting and ends
of the program. It is a universally accepted keyword in programming
language and cannot change its meaning and name.
In C
return _type main()
{
// main body
}
Alternate
return _type main()
{
# main body
/}

24. Thanks!
“if you lie to the Compiler;
It will get its revenge”
#Henry Spencer