Made by: -
Deopura karan 130410107014
Submitted to: -
Nidhi shah

What is compiler?
 Compiler is a program which takes one language as input and translate it into
an equivalent another language.
 Compiler is divided into two parts: Analysis and Synthesis
 Basic model of compiler can be represented as follows:

 Conceptually, a compiler operates into phases, each of which transform the
source program from one representation to another.
 Each phase takes input from its previous stage, has its own representation of source
program, and feeds its output to the next phase of the compiler.
 The compiler has six phases called as lexical analyzer, syntax analyzer,
semantic analyzer, intermediate code generator, code optimizer and code
generator.
 Two other activities, symbol-table management and error handling, are
interacting with the six phases of compiler.
Phases of compiler

Phases of compiler

 To support the phases of compiler, symbol table is maintained. The task of
symbol table is to store identifiers used in program.
 Basically symbol table is a data structure used to store the information
about identifiers.
 The symbol table allows us to find the record for each identifier quickly and
to store or retrieve data from that record efficiently.
 While doing the semantic analysis and intermediate code generation, we
need to know what type of identifiers are.
 During code generation typically information about how much storage is
allocated to identifier is seen.
Symbol-table management

Error detection and reporting
 In compilation, each phase detects error. These errors must be reported to
error handler whose task is to handle the error so that the compilation can
proceed.
 Normally, the errors are reported in the form of message.
 Large number of error can be detected in syntax analysis phase. Such error
are known as syntax error.
 During semantic analysis, type mismatch kind of error is usually detected.

Lexical analysis
 The lexical analysis is also known as scanning.
 It is the phase of compilation in which the complete source code is scanned
and source program is broken up into group of strings called token.
 A token is sequence of character having a collective meaning.
 E.g. Total = count + rate
 After lexical analysis, the statement is broken up into series of tokens as
follows:
identifier total, assignment operator, identifier count, plus sign, identifier
rate

syntax analysis
 The syntax analysis is also known as parsing.
 In this phase token generated by lexical analysis are grouped together to form
a hierarchical structure known as syntax tree.

semantic analysis
 Once syntax is checked in the syntax analyzer phase the next phase i.e.
semantic analyzer determines the meaning of the source string.
 For example meaning of source string means matching parenthesis, matching
if…else statement, performing arithmetic operation of expression that are type
compatible or checking operation scope.

Intermediate code generation
 The intermediate code is a kind of code which is easy to generate and this
code can be easily converted to target code.
 This code is in variety of form such as three address code, quadruple, triple,
posix.
 For example, total = count + rate * 10
 Intermediate code using three address code method is
t1 := int_to_float(10)
t2 := rate * t1
t3 := count + t2
total := t3

Code optimization
 The code optimization phase attempt to improve the intermediate code
 This is necessary to have a faster executing code or less consumption of
memory
 Thus, by optimizing the code the overall running time of the target program
can be improved.

Code generation
 In this phase, target code is generated.
 The intermediate code instructions are translated into sequence of machine
instruction
 For example, total = count + rate * 10
 Target code will be
MOV rate, R1
MUL #10.0, R1
MOV count, R2
ADD R2, R1
MOV R1, total