A compiler is a program that translates source code written in one programming language into another language. It performs two main tasks: analysis of the source program and synthesis of a machine-language program. The structure of a compiler typically includes a scanner, parser, semantic routines, code generator, and optimizer. The scanner reads the source code and groups characters into tokens. The parser checks the syntax against a grammar. Semantic routines perform static checking and translation. The code generator produces target code, which may then be optimized. An example compiler output is shown translating a sample program into assembly code.

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2. COMPILER
A compiler is a computer program that transforms
source code written in a programming language (the
source language) into another computer language (the
target language), with the latter takes binary form
known as object code
It create an executable program
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3. Cause
Software for early computers was written in
assembly language
The benefits of reusing software on
different CPUs started to become
significantly greater than the cost of writing
a compiler
The first real compiler
FORTRAN compilers of the late 1950s
18 person-years to build
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4. Any compiler must perform two major tasks
Analysis of the source program
Synthesis of a machine-language program
Structure of Compiler
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5. THE STRUCTURE OF A COMPILER (2)
5
Scanner Parser
Semantic
Routines
Code
Generator
Optimizer
Source
Program Tokens Syntactic
Structure
Symbol and
Attribute
Tables
(Used by all Phases of The Compiler)
(Character Stream)
Intermediate
Representation
Target machine code

6. THE STRUCTURE OF A COMPILER (3)
6
Scanner Parser
Semantic
Routines
Code
Generator
Optimizer
Source
Program Tokens Syntactic
Structure
Symbol and
Attribute
Tables
(Used by all
Phases of
The Compiler)
Scanner
 The scanner begins the analysis of the source program by
reading the input, character by character, and grouping
characters into individual words and symbols (tokens)
 RE ( Regular expression )
 NFA ( Non-deterministic Finite Automata )
 DFA ( Deterministic Finite Automata )
 LEX
(Character Stream)
Intermediate
Representation
Target machine code

7. THE STRUCTURE OF A COMPILER (4)
7
Scanner Parser
Semantic
Routines
Code
Generator
Optimizer
Source
Program Tokens Syntactic
Structure
Symbol and
Attribute
Tables
(Used by all
Phases of
The Compiler)
Parser
 Given a formal syntax specification (typically as a [CFG] ),
the parse reads tokens and groups them icontext-free
grammar nto units as specified by the productions of the
CFG being used.
 As syntactic structure is recognized, the parser either calls
corresponding semantic routines directly or builds a syntax
tree.
 CFG ( Context-Free Grammar )
 BNF ( Backus-Naur Form )
 GAA ( Grammar Analysis Algorithms )
 LL, LR, SLR, LALR Parsers
 YACC
(Character Stream)
Intermediate
Representation
Target machine code

8. THE STRUCTURE OF A COMPILER (5)
8
Scanner Parser
Semantic
Routines
Code
Generator
Optimizer
Source
Program
(Character Stream)
Tokens Syntactic
Structure
Intermediate
Representation
Symbol and
Attribute
Tables
(Used by all
Phases of
The Compiler)
Semantic Routines
 Perform two functions
 Check the static semantics of each construct
 Do the actual translation
 The heart of a compiler
 Syntax Directed Translation
 Semantic Processing Techniques
 IR (Intermediate Representation)
Target machine code

9. THE STRUCTURE OF A COMPILER (6)
9
Scanner Parser
Semantic
Routines
Code
Generator
Optimizer
Source
Program Tokens Syntactic
Structure
Symbol and
Attribute
Tables
(Used by all
Phases of
The Compiler)
Optimizer
 The IR code generated by the semantic routines is
analyzed and transformed into functionally equivalent but
improved IR code
 This phase can be very complex and slow
 Peephole optimization
 loop optimization, register allocation, code scheduling
 Register and Temporary Management
 Peephole Optimization
(Character Stream)
Intermediate
Representation
Target machine code

10. THE STRUCTURE OF A COMPILER (7)
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Source
Program
(Character Stream)
Scanner
Tokens
Parser
Syntactic
Structure
Semantic
Routines
Intermediate
Representation
Optimizer
Code
Generator
Code Generator
 Interpretive Code Generation
 Generating Code from Tree/Dag
 Grammar-Based Code Generator
Target machine code

11. THE STRUCTURE OF A COMPILER (8)
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Scanner
[Lexical Analyzer]
Parser
[Syntax Analyzer]
Semantic Process
[Semantic analyzer]
Code Generator
[Intermediate Code Generator]
Code Optimizer
Tokens
Parse tree
Abstract Syntax Tree w/ Attributes
Non-optimized Intermediate Cod
Optimized Intermediate Code
Code Optimizer
Target machine code

12. Language Description
Identifier Rules
•Identifier can be of maximum length 6.
•Identifiers are not case sensitive.
•An Indetifier can only have alphanumeric characters( a-z
, A-Z , 0-9 ) and underscore(_).
•The first character of an identifier can only contain
alphabet( a-z , A-Z ).
•Keywords are not allowed to be used as Identifiers.
•No special characters, such as semicolon, period,
whitespaces, slash or comma are permitted to be used in
or as Identifier.
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13. Data Types:
Our language supports only 3 datatypes
•Integer
•String
•Character
Expressions
1.Arithmetic operators (+, -, *, /, %)
2.Uniray operator
3.Paranthesis
4.Only Integer supported
5.Relational expression to be supported (>, <, >=, <=, ==, !=)
6. Character string and integer constants
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14. Statements
•Declaration statement : int a;
•Declaration and Initialisation : int a=5;
•Assingment Statement : a=6;
Conditional statement
Simple if (nesting not allowed)
if then
Endif
Switch Statement (nesting not allowed)
Switch()
Cases
Value 1:
Break;
Value n:
break;
Endcase
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15. Repetition Statement (nesting not allowed)
a.Repeat
Until ()
a.While (relational expression)
Endwhile
a.For = start value, end value, inc/dec
………
Endfor
4
I/O Statement
•Input ;
•Output ;
Program Structure
Decleration:
Start
End 15

16. 1.Sample Program I
#mode 10
declaration
int r
int c
int in
int flg
start
r = 0
flg = 1
while( flg == 1 )
if( c == 0) then
flg = 0
endif
c = c-1
endwhile
end
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17. OUTPUT 1
START:
MOV AX, @DATA
MOV DS, AX
MOV AX,
MOV r, AX
MOV AX,
MOV flg, AX
LB01:
MOV AX,
CMP AX,
JNE LB01
MOV AX,
CMP AX,
JNE LB01
MOV AX,
MOV flg, AX
LB02:
MOV AX,
SUB AX,
MOV c, AX
JMP LB01
LB03:
MOV AX, 4C00H
INT 21H
END START
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18. Sample Program II
#mode 10
declaration
int a ; b
int i
int k
string mes1
start
k=k*1
if(i<9 )then
i=i+9
k=k*1
endif
i=i-45
repeat
i=i+9*k+b
k=k*1
output "Hello World"
input k
until(i<2 )
while(k>3 )
i=i+9
k=k*1 endwhile
end
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19. OUTPUT
START:
MOV AX, @DATA
MOV DS, AX
MOV AX, k
MUL 1
MOV k, AX
MOV AX, i
CMP AX, 9
JGE LB01
MOV AX, i
ADD AX, 9
MOV i, AX
MOV AX, k
MUL 1
MOV k, AX
LB01:
MOV AX, i
SUB AX, 45
MOV i, AX
LB02:
MOV AX, i
ADD AX, 9
MUL k
ADD AX, b
MOV i, AX
MOV AX, k
MUL 1
MOV k, AX 19

20. OUTPUT
LEA DX, "Hello World"
CALL MESSAGE
CALL INDEC
MOV k, AX
MOV AX, i
CMP AX, 2
JGE LB01
LB03:
MOV AX,
CMP AX, 3
JLE LB01
MOV AX, i
ADD AX, 9
MOV i, AX
MOV AX, k
MUL 1
MOV k, AX
JMP LB01
MOV AX, i
ADD AX, 9
MOV i, AX
MOV AX, k
MUL 1
MOV k, AX
JMP LB01
LB04:
MOV AX, 4C00H
INT 21H
END START
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21. SCREENSHOTS
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24. Feasibility and future scope
With the growth of technology ease of working is given
priority.
We have emerged from C , C++ to python ,ruby , etc. which
require less lines of code .
Our project can be extended to form a new language which is
easy to learn, faster , has more inbuilt features and has many
more qualities of a good programming language.
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25. Conclusion
In a compiler the process of Intermediate code generation is
independent of machine and the process of conversion of
Intermediate code to target code is independent of language
used.
Thus we have done the front end of compilation process.
It includes 3 phases of compilation
lexical analysis
syntax analysis
semantic analysis
Followed by intermediate code generation.
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26. References
•Salomaa, Arto [1973]. Formal Languages. Academic Press,
New York
•Schulz, Waldean A. [1976]. Semantic Analysis and Target
Language Synthesis in a Translator.Ph.D. thesis, University of
Colorado, Boulder, CO.
•https://www.cs.vt.edu/undergraduate/courses/CS4304
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