Chapter 12-CL-2oP PDF

Computer Fundamentals: Pradeep K.
Sinha & Priti Sinha
Computer Fundamentals
Pradeep K. Sinha
Priti Sinha
Chapter 12
Computer
Chapter 12: Computer Languages
Languages Slide 1/64
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Learning Objectives
In this chapter you will learn about:

Computer languages or programming languages
Three broad categories of programming languages
machine, assembly, and high-level languages
Commonly used programming language tools such as
assembler, compiler, linker, and interpreter
Concepts of object-oriented programming languages
Some popular programming languages such as
FORTRAN, COBOL, BASIC, Pascal, C, C++, C#, Java,
RPG, LISP and SNOBOL
Related concepts such as Subprogram, Characteristics of
a good programming language, and factors to consider
while selecting a language for coding an application
Chapter 12: Computer Languages Slide 2/64
1
Analogy with
Natural Languages
Analogy with Natural Languages
Language is a means of communication

Programmer uses a computer language to instruct a computer
what he/she wants it to do
Set of words allowed in a language is called its vocabulary
Each word in the vocabulary has a definite unambiguous
meaning
Most computer languages use a very limited vocabulary
Words and symbols of a computer language must be used as
per the set rules, known as syntax rules
Ref. Page 220 Chapter 12: Computer Languages Slide 4/64
2
Broad Classification of Computer Languages
Machine language
Assembly language
High-level language
Machine Language
3
Machine Language
Machine language programs are written normally as strings

of binary 1s and 0s
Circuitry of a computer is wired in a manner that it
recognizes the machine language instructions and converts
them into electrical signals needed to execute them
A machine language instruction normally has a two-part
format: operation code tells the computer what function to
perform, and operand tells where to find or store the data
OPCODE OPERAND
(operation code) (address/location)
Instruction format
(Continued on next slide)
Machine Language
Every computer has a set of operation codes called its

instruction set
Typical operations included in the instruction set are:
Arithmetic operations
Logical operations
Branch operations
Data movement operations between memory locations and
registers
Data movement operations from/to input/output devices
4
A Sample Machine Language Program
001000000000001100111001 10001471
001100000000010000100001 14002041
011000000000011100101110 30003456
101000111111011100101110 50773456
000000000000000000000000 00000000
In Binary In Decimal
(Difficult to read and understand) (Easier to read and understand)

Advantages & Limitations of
Machine Language
Advantage
Can be executed very fast
Limitations
Machine dependent
Difficult to program
Error prone
Difficult to modify
5
Assembly Language
Assembly Language
Assembly language programming helped in overcoming

limitations of machine language programming
By using alphanumeric mnemonic codes instead of numeric
codes for instructions in instruction set
Allowing use of alphanumeric names instead of numeric
addresses
Providing additional instructions, called pseudo-instructions
A language that allows use of letters and symbols instead of
numbers for representing instructions and storage locations is
called assembly language or symbolic language
A program written in an assembly language is called assembly
language program or symbolic program
6
Sample Assembly Language Program
START PROGRAM AT 0000

START DATA AT 1000
SET ASIDE AN ADDRESS FOR FRST
SET ASIDE AN ADDRESS FOR SCND
SET ASIDE AN ADDRESS FOR ANSR
CLA FRST
ADD SCND
STA ANSR
HLT
Assembler
We must convert an assembly language program into its

equivalent machine language program before executing it
Translator program called assembler does this translation
Assembler is system software supplied by computer
manufacturers
Assembly language Input Output Machine language

Assembler
program program
One-to-one correspondence
(Source program) (Object program)
7
Advantages of Assembly Language
Over Machine Language
Easier to understand and use

Easier to locate and correct errors
Easier to modify
No worry about addresses
Easily relocatable
Efficiency of machine language
Limitations of Assembly Language
Machine dependent
Knowledge of hardware required
Machine level coding
8
Typical Uses of Assembly Language
Mainly used today to fine-tune important parts of

programs written in a high-level language to improve
the programs execution efficiency

Assembly Languages with
Macro Instructions
Any assembly language instruction that gets translated

into several machine language instructions is called a
macro instruction
Several assembly languages support such macro
instructions to speed up the coding process
Assemblers of such assembly languages are designed to
produce multiple machine language instructions for each
macro instruction of the assembly language
9
High-level Language
High-Level Languages
Machine independent
Do not require programmers to know anything about the
internal structure of computer on which high-level
language programs will be executed
Deal with high-level coding, enabling the programmers
to write instructions using English words and familiar
mathematical symbols and expressions
10
Compiler
Translator program (software) that translates a high-

level language program into its equivalent machine
language program
Compiles a set of machine language instructions for
every program instruction in a high-level language
Compiler
Input Output
High-level language Compiler Machine language
program program
One-to-many correspondence
(Source program) (Object program)
11
Separate Compiler for Each High-level
Language Supported
Program P1 in high- Compiler for

level language L1 language L1 Machine code for P1
Program P2 in high- Compiler for

level language L2 language L2 Machine code for P2
A computer supporting languages L1 and L2

A High-level Language is Machine
Independent
Compiler for Machine code for

language L1 P1 that will run Executed on
on computer A on computer A computer A
Program P1 in high-
level language L1 Same results obtained
Compiler for Machine code for

language L1 P1 that will run Executed on
on computer B on computer B computer B
12
Syntax Errors
In addition to doing translation job, compilers also

automatically detect and indicate syntax errors
Syntax errors are typically of following types:
Illegal characters
Illegal combination of characters
Improper sequencing of instructions in a program
Use of undefined variable names
Note : A compiler cannot detect logic errors in a program

The Process of Removing Syntax Errors
From A Source Program
START
Edit
source program
Source program
Compile
source program
Syntax
No Generate
errors
detected? object program
Yes Object program

Generate list of coded STOP
error messages
13
Linker
For a large software, storing all the lines of program

code in a single source file will be:
Difficult to work with

Difficult to deploy multiple programmers to
concurrently work towards its development
Any change in the source program would require the
entire source program to be recompiled
Hence, a modular approach is generally adapted to

develop large software where the software consists of
multiple source program files
No need to write programs for some modules as it might
be available in library offering the same functionality
Linker
Each source program file can be independently

modified and compiled to create a corresponding
object program file
Linker program (software) is used to properly
combine all the object program files (modules)
Creates the final executable program (load module)
14
Linker
Prog-1.src Prog-2.src Prog-n.src Source programs
Compilation
process
Prog-1.obj Prog-2.obj Prog-n.obj Object programs
Prog-i.lib Library modules
Linking
process
Executable Load module

program file
Interpreter
Interpreter is a high-level language translator

Takes one statement of a high-level language
program, translates it into machine language
instructions
Immediately executes the resulting machine language
instructions
Compiler simply translates the entire source program
into an object program and is not involved in its
execution
15
Interpreter
High-level Input Output Result of

Interpreter (translates and executes
language program
statement-by-statement)
program execution
(Source program)
Interpreter
As compared to compilers, interpreters are easier to write

The main advantage of interpreters over compilers is that an
interpreter flags a syntax error in a program statement to a
programmer as soon as it interprets the program statement
Main disadvantage of interpreters over compilers is that they
are slower than compilers
To combine the advantages of both interpreters and
compilers, computer system provides both a compiler and an
interpreter for a high-level language
Assemblers, compilers, and interpreters are also referred to
as language processors
16
Intermediate Language Compiler &
Interpreter
New type of compiler and interpreter combines the
speed, ease, and control of both compiler and
interpreter
Compiler first compiles the source program to an
intermediate object program
Intermediate object program is not a machine
language code but written in an intermediate
language that is virtually machine independent
Interpreter takes intermediate object program,
converts it into machine language program and
executes it

Benefits of Intermediate Language
Compiler & Interpreter
Intermediate object program is in compiled form and thus is

not original source code, so safer and easier to share
Intermediate object program is based on a standard
Intermediate Definition Language (IDL)
Interpreter can be written for any computer architecture and
operating system providing virtual machine environment to the
executing program
Newer Interpreter compiles intermediate program, in memory,
into final host machine language program and executes it
This technique is called Just-In-Time (JIT) Compilation
17
Advantages of High-Level Languages
Machine independent
Easier to learn and use
Fewer errors during program development
Lower program preparation cost
Better documentation
Easier to maintain
Limitations of High-Level Languages
Lower execution efficiency

Less flexibility to control the computers CPU, memory
and registers
18
Object-Oriented
Languages

What is Object-Oriented Programming
(OOP)?
Essence of OOP is to solve a problem by:

Identifying the real-world objects of the problem and the
processing required of those objects
Then creating simulations of those objects, their processes,
and the required communications between the objects
OOP makes programming simpler, easier, and faster
OOP philosophy is now used in almost all popular
programming languages
19
Fundamental Concepts of OOP

Object
An object is the primitive element of a program written in an
OOP language
Each object consists of a set of procedures and some data
Method
A method of an object defines the set of operations that the
object will execute when it receives a message
Methods are like function definitions
Entire collection of methods of an object is called the message
protocol, or message interface
Message
Mechanism to support communication between objects is
through messages
Fundamental Concepts of OOP

Class
A class is a description of one or more similar objects
A class can have multiple instances
Each instance of a class is known as an object of the class
Class variables are variables stored in the class whose values
are shared by all instances
Instance variables are variables for which local storage is
available in the instances (objects)
Inheritance
Inheritance is a mechanism to share code and behavior
A child class inherits all of the instance variables, instance
methods, and class methods of its parent class
A child class can inherit from multiple parent classes. This is
called multiple inheritance
20
Example of Class, Instance, and
Inheritance
Person
Classes Male Female
Boy Man
Instances Ram Shyam Mohan Seeta Geeta

Example of Objects, Class, and
Inheritance
Object a
Class A (Instance of A)
Variables of A Class A
Methods of A Instance variables of A
Class B
(Sub-class of Object b
Class A) (Instance of B)
Inherits from A Class B
Variables of B Inherited instance variables of A
Methods of B Instance variables of B
21
Key Elements of Object-Oriented Paradigm
Sr.
Element Meaning
No.
1 Abstraction Abstraction means that an objects characteristics are broken
into manageable chunks as defined and documented in its
class description.
2 Encapsulation Encapsulation stipulates that code and data are stored as one
unit. Encapsulation also enables selective or total information
hiding, since it can make portions of the code and data
inaccessible from outside the unit.
3 Modularity Modularity defines the unit reuse. These units group
abstractions together.
4 Hierarchy Hierarchy allows an objects behaviors to be refined
(subclasses) without recoding of the parent object (the
superclass). Some OO languages allow an object to have
more than one superclass, a feature that is known as multiple
inheritance. Inheritance hierarchies enable ranking/ordering
of abstractions.
5 Messages Messages, similar in use to function calls, are requests to
perform an operation on an instantiated object.
Some High-level
Languages
22
FORTRAN
Stands for FORmula TRANslation

Originally developed by John Backus and his team at
IBM followed by several revisions
Standardized by ANSI as FORTRAN-77 and FORTRAN-90
Designed for solving scientific & engineering problems
Oriented towards solving problems of a mathematical
nature
Popular language amongst scientists and engineers
COBOL
Stands for COmmon Business Oriented Language

Originally developed started under Grace Hopper
followed by COnference on DAta SYstems Languages
(CODASYL)
Standardized by ANSI as COBOL-74, COBOL-85, and
COBOL-2002
Designed for programming business data processing
applications
Designed to have the appearance and structure of a
business report written in English, hence often referred
to as a self-documenting language
23
BASIC
Stands for Beginners All-purpose Symbolic Instruction

Code
Developed by Professor John Kemeny and Thomas Kurtz
at Darmouth College in the United States
Standardized by ANSI as BASIC-78
Designed to be an interactive language and to use an
interpreter instead of a compiler
Simple to implement, learn and use language. Hence, it
is a widely used language on personal computers
Flexible and reasonably powerful language and can be
used for both business and scientific applications
Pascal
Named after the famous seventeenth-century French

mathematician Blaise Pascal
Developed by Professor Nicklaus Wirth of Federal Institute of
Technology in Zurich
Encourages programmers to write well-structured, modular
programs, instills good program practices
Recognized as an educational language and is used to teach
programming to beginners
Suitable for both scientific & business applications
Has features to manipulate numbers, vectors, matrices,
strings, sets, records, files, and lists
24
Developed in 1972 at AT&Ts Bell laboratories, USA

by Dennis Ritchie and Brian Kernighan
Standardized by ANSI and ISO as C89, C90, C99
High-level programming languages (mainly machine
independence) with the efficiency of an assembly
language
Language of choice of programmers for portable
systems software and commercial software packages
like OS, compiler, spreadsheet, word processor, and
database management systems
C++ (C plus plus)
Named C++ as ++ is increment operator and C

language is incremented to its next level with C++
Developed by Bjarne Stroustrup at Bell Labs in the
early 1980s
Contains all elements of the basic C language
Expanded to include numerous object-oriented
programming features
Provides a collection of predefined classes, along with
the capability of user-defined classes
Being a superset of C, it is an extremely powerful and
efficient language. However, it is more difficult to learn
than C
25
Java
Development started at Sun Microsystems in 1991 by a

team led by James Gosling
Developed to be similar to C++ with fewer features to
keep it simple and easy to use
Compiled code is machine-independent and developed
programs are simple to implement and use
Uses just-in-time compilation
Used in embedded systems such as hand-held devices,
telephones and VCRs
Comes in two variants Java Runtime Engine (JRE) and
Java Software Development Kit (SDK)
C# (C Sharp)
Object-oriented programming language developed by

Anders Hejlsberg and released by Microsoft as part of
Microsofts .NET technology initiative
Standardized by ECMA and ISO
Syntactically and semantically very close to C++ and
adopts various object-oriented features from both C++
and Java
Compilers target the Common Language Infrastructure
(CLI) implemented by Common Language Runtime (CLR)
of .NET Framework
CLR provides important services such as, memory
management, exception handling, and security
26
RPG
Stands for Report Program Generator

Developed by IBM to meet customer requests for an
easy and economic mechanism for producing reports
Designed to generate the output reports resulting from
the processing of common business applications
Easier to learn and use as compared to COBOL
Programmers use very detailed coding sheets to write
specifications about input, calculations, and output
LISP
Stands for LISt Processing

Developed in 1959 by John McCarthy of MIT
Designed to have features for manipulating non-
numeric data, such as symbols and strings of text
Due to its powerful list processing capability, it is
extensively used in the areas of pattern recognition,
artificial intelligence, and for simulation of games
Functional programming language in which all
computation is accomplished by applying functions to
arguments
27
SNOBOL
Stands for StriNg Oriented symBOlic Language

Used for non-numeric applications
Powerful string manipulation features
Widely used for applications in the area of text
processing
Selecting a Language for

Coding an Application
28
Characteristics of a Good
Programming Language
Simplicity
Naturalness
Abstraction
Efficiency
Structured Programming Support
Compactness
Locality
Extensibility
Suitability to its environment

Factors for Selecting a Language for
Coding an Application
Nature of the application

Familiarity with the language
Ease of learning the language
Availability of program development tools
Execution efficiency
Features of a good programming language
29
Subprogram
Subprogram
Program written in a manner that it can be brought into

use in other programs and used whenever needed
without rewriting
Also referred to as subroutine, sub-procedure, or function
Subprogram call statement contains the name of the
subprogram followed by a list of parameters enclosed
within a pair of parentheses
Intrinsic subprograms (also called built-in-functions) are
those provided with the programming language
Programmer-written subprograms are written and used
as and when they are needed
30
Structure of a Subprogram
Subprogram name Parameter
Subprogram header
sqrt (x)
Set of instructions that perform Subprogram body

the intended task
Flow of Control in Case of Subprogram Calls
1 2 subprogram header
subprogram call statement 6

next statement 4 3
subprogram body
7
5
subprogram call statement

next statement 8
9
A program that calls Flow of control A subprogram

the subprogram twice
31
Key Words/Phrases
Assembler Just-in-time compilation

Assembly language Language processor
BASIC Linker
Built-in function LISP
C Load module
C++ Logic error
C# Low-level language
COBOL Machine language
Coding Macro instructions
Compiler Object program
Computer language Object-oriented programming
FORTRAN Opcode
Function Operand
High-level language Pascal
HotJava Interpreter Programmer
Intrinsic subprogram Programming
Intermediate compiler and Programming language
Interpreter Pseudo instruction
Java RPG
Self-documenting language
Key Words/Phrases
SNOBOL
Source program
Sub-procedure
Subprogram
Subroutine
Symbolic language
Syntax error
Syntax rules
Programmer-written subprograms
32

Chapter 12-CL-2oP PDF

Uploaded by

Copyright:

Available Formats

Chapter 12-CL-2oP PDF

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Chapter 12-CL-2oP PDF

Uploaded by

Copyright:

Available Formats

Computer Fundamentals: Pradeep K.

Sinha & Priti Sinha

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

In this chapter you will learn about:

Chapter 12: Computer Languages Slide 2/64

Chapter 12: Computer Languages Slide 3/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Analogy with Natural Languages

Language is a means of communication

Ref. Page 220 Chapter 12: Computer Languages Slide 4/64

Broad Classification of Computer Languages

Ref. Page 221 Chapter 12: Computer Languages Slide 5/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Chapter 12: Computer Languages Slide 6/64

Machine language programs are written normally as strings

Ref. Page 221 Chapter 12: Computer Languages Slide 7/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Every computer has a set of operation codes called its

Ref. Page 221 Chapter 12: Computer Languages Slide 8/64

A Sample Machine Language Program

Ref. Page 222 Chapter 12: Computer Languages Slide 9/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Can be executed very fast

Ref. Page 222 Chapter 12: Computer Languages Slide 10/64

Chapter 12: Computer Languages Slide 11/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Assembly language programming helped in overcoming

Ref. Page 223 Chapter 12: Computer Languages Slide 12/64

Sample Assembly Language Program

START PROGRAM AT 0000

Ref. Page 223 Chapter 12: Computer Languages Slide 13/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

We must convert an assembly language program into its

Assembly language Input Output Machine language

Ref. Page 224 Chapter 12: Computer Languages Slide 14/64

Easier to understand and use

Ref. Page 226 Chapter 12: Computer Languages Slide 15/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Limitations of Assembly Language

Ref. Page 227 Chapter 12: Computer Languages Slide 16/64

Typical Uses of Assembly Language

Mainly used today to fine-tune important parts of

Ref. Page 228 Chapter 12: Computer Languages Slide 17/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Any assembly language instruction that gets translated

Ref. Page 228 Chapter 12: Computer Languages Slide 18/64

Chapter 12: Computer Languages Slide 19/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Ref. Page 228 Chapter 12: Computer Languages Slide 20/64

Translator program (software) that translates a high-

Ref. Page 229 Chapter 12: Computer Languages Slide 21/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha

Ref. Page 230 Chapter 12: Computer Languages Slide 22/64

Program P1 in high- Compiler for

Program P2 in high- Compiler for

A computer supporting languages L1 and L2

(Continued on next slide)

Ref. Page 230 Chapter 12: Computer Languages Slide 23/64

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha