Basic Of Compiler Construction

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1
Assignment 1
Question 1
Write in detail about translators and its types
Answer
Translator:
A translator or programming language processor is a computer program that
performs the translation of a program written in a given programming language
into a functionally equivalent program in another computer language, without
losing the functional or logical structure of the original code.
A program written in high-level language is called as source code. To convert the
source code into machine code, translators are needed.
Types of Translator
1. Compiler
2. Interpreter
3. Assembler
Compiler: Compiler is a translator which is used to convert programs in highlevel language to low-level language. It translates the entire program and also
reports the errors in source program encountered during the translation. A
compiler is a program that can read a program in one language the source
language and translate it into an equivalent program in another language the
target language. An important role of the compiler is to report any errors in the
source program that it detects during the translation process.
Interpreter: Interpreter is a translator which is used to convert programs in
high-level language to low-level language. Interpreter translates line by line and
reports the error once it encountered during the translation process. An
interpreter is another common kind of language processor. Instead of producing a
target program as a translation, an interpreter appears to directly execute the
operations specified in the source program on inputs supplied by the user.
Assembler: Assembler is a translator which is used to translate the assembly
language code into machine language code. An assembler is a type of computer
program that interprets software programs written in assembly language into
machine language, code and instructions that can be executed by a computer.
An assembler enables software and application developers to access, operate and
manage a computer's hardware architecture and components.
An assembler is sometimes referred to as the compiler of assembly language. It
also provides the services of an interpreter.
Question 2
Compare the translators in detail
DAYAN AHMED
2
Assignment 1
Answer
Comparison between translators are as follows:
1. Complier and Interpreter.
S. No
Compiler
Interpreter
1
Performs the translation of a program
as a whole.
Performs statement by statement
translation.
2
Execution is faster.
Execution is slower.
3
Requires more memory as linking is
needed for the generated
intermediate object code.
Memory usage is efficient as no
intermediate object code is
generated.
4
Debugging is hard as the error
messages are generated after scanning
the entire program only.
It stops translation when the first
error is met. Hence, debugging is
easy.
5
Programming languages like C, C++
uses compilers.
Programming languages like Python,
BASIC, and Ruby uses interpreters.
2. Interpreter and Assembler.
S. No
Interpreter
Assembler
1
Software that translates high
language program into machine
language.
Software that converts program
written in assembly language into
machine language.
2
Converts the high language program
to machine language line by line.
Converts assembly language program
to machine language.
Most interpreters can complete the
execution of a program by
themselves.
Assemblers produce an object code,
which might have to be linked using
linker programs in order to run on a
machine
Used by Ruby, Perl, Python, PHP
Used by assembly language.
3
4
3. Assembler and Compiler.
DAYAN AHMED
3
Assignment 1
S. No
COMPILER
ASSEMBLER
1
Generates the assembly language code or
directly the executable code.
Generates the relocate-able
machine code.
2
Preprocessed source code.
Assembly language code.
3
The compilation phases are lexical analyzer, Assembler makes two passes
syntax analyzer, semantic analyzer,
over the given input.
intermediate code generation, code
optimization, code generation.
4
The assembly code generated by the
compiler is a mnemonic version of machine
code.
The relocate-able machine
code generated by an
assembler is represented by
binary code.
Question 3
What are the Techniques and Methodology Used by compiler?
Answer
If we have treated a compiler as a single box that maps a source program into a
semantically equivalent target program. If we open up this box a little, we see that there
are two parts to this mapping: analysis and synthesis.
The analysis part breaks up the source program into constituent pieces and imposes a
grammatical structure on them. It then uses this structure to create an intermediate
representation of the source program. If the analysis part detects that the source
program is either syntactically ill formed or semantically unsound, then it must provide
informative messages, so the user can take corrective action. The analysis part also
collects information about the source program and stores it in a data structure called a
symbol table, which is passed along with the intermediate representation to the synthesis
part.
The synthesis part constructs the desired target program from the intermediate
representation and the information in the symbol table. The analysis part is often called
the front end of the compiler; the synthesis part is the back end. If we examine the
compilation process in more detail, we see that it operates as a sequence of phases, each
of which transforms one representation of the source program to another. A typical
decomposition of a compiler into phases is shown below.
DAYAN AHMED
4
Assignment 1
In practice, several phases may be
grouped together, and the
intermediate representations
between the grouped phases need not
be constructed explicitly. The symbol
table, which stores information about
the entire source program, is used by
all phases of the compiler. Some
compilers have a machineindependent optimization phase
between the front end and the back
end. The purpose of this optimization
phase is to perform transformations
on the intermediate representation,
so that the back end can produce a
better target program than it would
have otherwise produced from an
unoptimized intermediate
representation. Since optimization is
optional, one or the other of the two optimization phases may be missing.
Question 4
Why understanding Theory of automata is necessary to
understand/develop a compiler?
Answer
Importance of Theory of Automata to understanding a Complier:
Theory of Automata plays a vital role in understanding the compiler construction. Many
concepts of Automata recalls to understand the compiler construction. Here is the
example Finite Automata.
Finite Automata are used two of the three front-end phases of the compiler.
The first phase, Lexical Analysis, uses Regular Expressions to tokenize the input.
Regular expressions are usually implemented with Finite Automata.
DAYAN AHMED
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