Lectures in :
Compilers
Principles & Techniques
By
Uni.Al-Anbar,Computers College
Dr. Esam T. Yassen
Adapted By
Dr.Sameeh Abdulghafour Jasim
Uni. of Al-MAARIF, Col. of
Sciences
Lecture 1
Compilers
Principle ,Techniques, and Tools
With My Best Wishes 1
Introduction
Programming languages :-
Interactions involving humans are most effectively carried out
through the medium of language . language permits the expression of
thoughts and ideas , and without it , communication as we know it
would be very difficult indeed .
In computer programming , programming language serves as
means of communication between the person with a problem and the
computer used to solve it . programming language is a set of symbols ,
words , and rules used to instruct the computer .
A hierarchy of programming languages based on increasing
machine independence include the following :-
1- machine language : is the actual language in which the
computer carries out the instructions of program . otherwise , " it is
the lowest from of computer language , each instruction in
program is represented by numeric cod , and numeric of addresses
are used throughout the program to refer to memory location in the
computer memory .
2- Assembly languages : is a symbolic version of a machine
language ,each operation code is given a symbolic code such a
Add , SUB ,…. Moreover , memory location are given symbolic
name , such as PAY , RATE .
3-high – level language :Is a programming language where the
programming not require knowledge of the actual computing
machine to write a program in the language .H.L.L . offer a more
enriched set of language features such as control structures , nested
statements , block …
4- problem-oriented language : It provides for the expression of
problems in a specific application . Examples of such language
are SQL for Database application and COGO for civil engineering
applications .
University of Al-MAARIF, Col. of Sciences
Esam & Sameeh
Compilers
Principle ,Techniques, and Tools
With My Best Wishes 2
Advantages of H.L.L over L.L.L include the following :
1- H.L.L are easier to learn then L.L.L
2- A programmer is not required to know how to convert data
from external from to internal within memory .
3- Most H.L.L offer a programmer a variety of control structures
which are not available in L.L.L
4- Programs written in H.L.L are usually more easily debugged
than L.L.L. equivalents.
5- Most H.L.L offer more powerful data structure than L.L.L.
6- Finally ,High level languages are relatively machineindependent. Consequently certain programs are portable
Translator: High- Level language programs must be translated
automatically to equivalent machine- language programs .
A translator input and then converts a " source program" into an object
or target program . the source program is written in a source language
and the object program belong to an object language .
| Source program |
Translator | Object program |
1- If the source program is written in assembly language and the
target program in machine language .the translator is
called " Assembler "
2- If the source language is H.L.L. and the object language is L.L.L.
,then the translator is called " Compiler " .
3- If the source language is L.L.L. and the object language is H.L.L.,
then the translator is called "Decompiler"
Source Object Executing
Compiler Result
program program computer
compile Time run Time
(compilation Process)
University of Al-MAARIF, Col. of Sciences
Esam & Sameeh
Compilers
Principle ,Techniques, and Tools
With My Best Wishes 3
- The time at which conversion of a source program to an object
program occurs is called " Compile time " .The object program is
executed at " Run time " ,note that the source program and data
are process at different time .
Another kind of translator ,called an " Interpreter " in which
processes an internal form of source program and data at the same
time . that is interpretation of the internal source from occurs at run
time and no object program is generated .
Data
Source Program Interpreter Result
( Interpretive process )
Compiled programs usually run faster than interpreter ones
because the overhead of understanding and translating has already
been done .However ,Interpreters are frequent easier to write than
Compilers , and can more easily support interactive debugging of
program .
Remark :Some programming language implementations support
both interpretation and compilation.
A bad workman quarrels his
tools
University of Al-MAARIF, Col. of Sciences
Esam & Sameeh
