Languages and Os

8/8/2019 Languages and Os

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Compiled by :Compiled by :

S. Agarwal,S. Agarwal,Lecturer & Systems InchargeLecturer & Systems Incharge

St. Xaviers Computer Centre,St. Xaviers Computer Centre,

St. Xaviers CollegeSt. Xaviers College

Kolkata.Kolkata.

March-2003


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WHAT IS PROGRAMWHAT IS PROGRAM

A program is a sequence of instructions that a

computer can interpret and execute. It is developed

using high level computer languages.

WHAT IS SOFTWAREWHAT IS SOFTWARE

Software is computer program or a set of programs, which provides the instructions which

enable the computer hardware to work. Two main

types of software are system software (operatingsystems), which control the workings of the

computer, and applications, such as word

processing programs, spreadsheets, and databases.


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Types of Languages Used toTypes of Languages Used to

Write a SoftwareWrite a Software

Machine LanguageMachine Language

Assembly LanguageAssembly Language

High Level LanguageHigh Level Language


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Machine LanguageMachine Language

A set of machine instructions written using binary code that a processorA set of machine instructions written using binary code that a processorcan understand.can understand.

A processor interprets and translates machine instructions into HWA processor interprets and translates machine instructions into HWsignals.signals.

Example:Example:the instruction to add 2 numbers stored in registers A and B might lookthe instruction to add 2 numbers stored in registers A and B might looklike this:like this:

00000011 1100001100000011 11000011Problems:Problems: Binary representation of instructions and data are not easily generated,Binary representation of instructions and data are not easily generated,

manipulated, or understood by humans.manipulated, or understood by humans. The languages are machine dependent.The languages are machine dependent. Writing program in machine language requires the knowledge of theWriting program in machine language requires the knowledge of the

internals of the computer.internals of the computer.


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Assembly LanguageAssembly Language

AA symbolic formsymb

olic form of machine languageof machine language Allows alphabeticAllows alphabetic mnemonicsmnemonics for operation codes andfor operation codes and

storage locationsstorage locations There exists one-to-one correspondence betweenThere exists one-to-one correspondence betweenassembly instructions and machine instructions.assembly instructions and machine instructions.

Example:

M. L. Instruction:M. L. Instruction: 00000011 1100001100000011 11000011

Equivalent A.L. Instruction:Equivalent A.L. Instruction: ADD A, BADD A, B


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Advantages .Advantages .

Ease: Because of the use of mnemonics it isEase: Because of the use of mnemonics it ismore understandable and easy to remembermore understandable and easy to rememberthan a machine language code..than a machine language code..

Speed: programs in AL run faster than thoseSpeed: programs in AL run faster than thosewritten in high level languages.written in high level languages.

Compactness: routines include only code thatCompactness: routines include only code that

programmers want to include.programmers want to include. Versatility: anything that can be done with aVersatility: anything that can be done with a

computer can be done with ALcomputer can be done with AL


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Problems .Problems .

Big programs in assembly language : harderBig programs in assembly language : harder

to write and error prone.to write and error prone.

The languages are machine dependent.The languages are machine dependent. The programmer must still be aware of theThe programmer must still be aware of the

internal architecture of the target machine.internal architecture of the target machine.


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High Level LanguageHigh Level Language

Use English like codes that are easier to remember.Use English like codes that are easier to remember. Generally machine (architecture)Generally machine (architecture) independent.independent. Provides language constructs for specifying andProvides language constructs for specifying and

manipulating complex data structures.manipulating complex data structures. Supports a variety of programming styles (i.e. linear,Supports a variety of programming styles (i.e. linear,

object oriented)object oriented) Hides the low level architectural details from theHides the low level architectural details from the

programmer i. e. dose not normally require theprogrammer i. e. dose not normally require the

knowledge of the internal architecture of the computers.knowledge of the internal architecture of the computers.

Example :Example : C, C++, Pascal, COBOL, JavaC, C++, Pascal, COBOL, Java


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Binary codesBinary codes

SomeSomebinary codes usedbinary codes used

to represent informationto represent information

in a digital computer:in a digital computer:

1) BCD Code1) BCD Code2) ASCII Code2) ASCII Code

3) Gray Code3) Gray Code

4) EBCDIC Code4) EBCDIC Code

5) Excess-3 Code5) Excess-3 Code


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BCD CODEBCD CODE

BCD stands forBCD stands for BBinary-inary-CCodedoded DDecimal.ecimal.

A BCD number is a four-bit binary groupA BCD number is a four-bit binary group

that represents one of the ten decimal digitsthat represents one of the ten decimal digits

0 through 9.0 through 9.Example:

Decimal number 4926 4 9 2 6

8421 BCD coded number 0100 1001 0010 0110


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THETHE ASCIIASCII CODECODE

ASCIIASCII is acronym foris acronym for AAmericanmerican SStandardtandard CCodeodeforfor IInformationnformation IInterchangenterchange

Represents numbers, letters, punctuation marksRepresents numbers, letters, punctuation marks

and control charactersand control characters Standard ASCII is a 7-bit code (127 characters)Standard ASCII is a 7-bit code (127 characters)

Extended ASCII (IBM ASCII), an 8-bit code, isExtended ASCII (IBM ASCII), an 8-bit code, is

also very popularalso very popular Extended ASCII adds graphics and math symbolsExtended ASCII adds graphics and math symbols

to code (total of 256 symbols)to code (total of 256 symbols)


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BIT PATTERN ASCII CODE CHARACTER

01000001 65 A

01100001 97 a

00110001 49 100101011 43 +

00100000 32

00101101 45 -

00011100 28 (

00101100 44 ,

ASCII : Example ..ASCII : Example ..


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0x000000 00100111101111011111111111100000

0x000004 10101111101111110000000000010100

0x000008 10101111101001000000000000100000

0x00000c 10101111101001010000000000100100

0x000010 10101111101000000000000000011000

0x000014 10101111101000000000000000011100

0x000018 10001111101011100000000000011100

0x00001c 00000001110011100000000000011001

0x000020 00000000000000000111100000010010

0x000024 10001111101110000000000000011000

0x000028 00000011000011111100100000100001

0x00002c 101011111010100000000000000111000x000030 00100101110010000000000000000001

0x000034 10101111101110010000000000011000

0x000038 00101001000000010000000001100101

0x00003c 00010100001000001111111111110111

0x000040 00111100000001000001000000000000

0x000044 00110100100001000000010000110000

0x000048 10001111101001010000000000011000

0x00004c 00001100000100000000000011101100

0x000050 00000000000000000001000000100001

0x000054 10001111101111110000000000010100

0x000058 00100111101111010000000000100000

0x00005c 00000011111000000000000000001000

TranslatorsTranslators

Used to translate otherUsed to translate other

forms of languages intoforms of languages into

machine language.machine language.

Three types of commonlyThree types of commonly

used translators are :used translators are :

1) Assembler1) Assembler

2) Compiler2) Compiler3) Interpreter3) Interpreter


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AssemblerAssembler

A program thatA program that converts assembly code into machine codeconverts assembly code into machine code

After translation creates object module i.e. the machine languageAfter translation creates object module i.e. the machine language

representation of a programrepresentation of a program


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How does an assembler work ?


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CompilerCompiler

Translates high-level code

into machine language code.

Produces object code

(Translated Instructions ready

for computer)) by translatingthe ssource code ( high-level

language instruction ).

Object code is stored in the

machine and can be usedrepeatedly.


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SOURCE CODESOURCE CODE

PROGRAMPROGRAM

COMPILERCOMPILER

OBJECT CODEOBJECT CODE

LINKAGELINKAGE

EDITOREDITOR

LOAD MODULELOAD MODULE

OTHER OBJECTOTHER OBJECT

CODE MODULESCODE MODULES

TRANSLATIONTRANSLATION

PROCESSPROCESS


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Digital Computer as a Multilevel MachineDigital Computer as a Multilevel Machine

High Level Language Level

Assembly Language Level

Operating System Level

Machine Language Level

Microprogram Level

Digital Logic Level

Translation(Compiler)

Translation(Assembler)

So

ftwar

e

Ha

rdw

ar

e

Machine code

Machine code

Partial Interpretation,

Partial Pass-through

Interpretation (microprogram)

Directly executed by hardware

Applications Level


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InterpreterInterpreter Like compiler translates a high level language into machine language.Like compiler translates a high level language into machine language.

Unlike compiler translates the program at the time of executing theUnlike compiler translates the program at the time of executing theprogram instruction by instruction.program instruction by instruction.

The translated code is not stored permanently in computers memory,The translated code is not stored permanently in computers memory,hence before each execution interpretation becomes necessary.hence before each execution interpretation becomes necessary.

As object code is not stored in the computer, execution of the programAs object code is not stored in the computer, execution of the program

becomes slower because of the need for interpretation before eachbecomes slower because of the need for interpretation before eachexecution.execution. Normally it is easier to design an interpreter than a compiler.Normally it is easier to design an interpreter than a compiler.


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Generations of LanguagesGenerations of Languages

1st. Since 1940s. MACHINE LANGUAGE: binary code.

2nd.Since early 50s. ASSEMBLY LANGUAGE:

mnemonics for numeric code.

3rd.Since mid 50s. HIGH-LEVEL LANGUAGES:procedural in nature.

e.g.C, C++, COBOL

4th.Since late 70s. MODERN APPLICATION PACKAGES:

non-procedural in nature. e.g. Structured Query Language (SQL)


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SYSTEM SOFTWARESYSTEM SOFTWARE

The system softwares are programs speciallyThe system softwares are programs specially

designed for controlling the computerdesigned for controlling the computer

hardware, ensuring the proper utilization of thehardware, ensuring the proper utilization of the

computer resources and providing a convenientcomputer resources and providing a convenient

environment to the users of the computer toenvironment to the users of the computer to

work with.work with.

Example:Example: Operating system, Compiler,Operating system, Compiler,

Interpreter, Loader, LinkerInterpreter, Loader, Linker


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APPLICATION SOFTWAREAPPLICATION SOFTWAREThese are programs developed by the users of the computer toThese are programs developed by the users of the computer to

perform a specific task. They can be of two types:perform a specific task. They can be of two types:

a) Ready Made:a) Ready Made:

These are programs developed by software companies for generalThese are programs developed by software companies for general

purpose applications. These programs can be bought and can bepurpose applications. These programs can be bought and can be

installed for performing some predefined job.installed for performing some predefined job.

Examples :Examples :MS-WORD, FACT, TALLY, FOXPRO etc.MS-WORD, FACT, TALLY, FOXPRO etc.

b) Customized or Tailor made :b) Customized or Tailor made :

These are programs developed for SPECIFIC USER REQUIREMENTThese are programs developed for SPECIFIC USER REQUIREMENT

within an organization. These programs are developed by programmerswithin an organization. These programs are developed by programmers

as per the user requirementsas per the user requirements..

Example:Example:Library Management System, Hotel Management System,Library Management System, Hotel Management System,

Railway Reservation SystemRailway Reservation System


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SOFTWARE LAYERSSOFTWARE LAYERS

HARDWARE

OPERATING SYSTEM:OPERATING SYSTEM:

SCHEDULED COMPUTER EVENTSSCHEDULED COMPUTER EVENTS

ALLOCATES COMPUTERALLOCATES COMPUTER

RESOURCESRESOURCES

MONITORS EVENTSMONITORS EVENTS

LANGUAGE TRANSLATORS:LANGUAGE TRANSLATORS:

INTERPRETERSINTERPRETERS

COMPILERSCOMPILERS

UTILITY PROGRAMS:UTILITY PROGRAMS:

ROUTINE OPERATIONSROUTINE OPERATIONS

MANAGE DATAMANAGE DATA

PROGRAMMING LANGUAGES:PROGRAMMING LANGUAGES:

ASSEMBLY LANGUAGE; FORTRAN;ASSEMBLY LANGUAGE; FORTRAN;

COBOL; PL / 1; QBASIC; PASCAL; C; C++;COBOL; PL / 1; QBASIC; PASCAL; C; C++;

FOURTH GENERATION LANGUAGESFOURTH GENERATION LANGUAGES

SYSTEM SOFTWARE

APPLICATION SOFTWARE


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Operating SystemOperating System

Interface managerInterface manager

Human interaction made easyHuman interaction made easy

interfacing, abstraction, controlinterfacing, abstraction, controland sharingand sharing Resource managerResource manager

Efficient use of resourcesEfficient use of resources System and data security andSystem and data security and

protection provider.protection provider. Control program that prevents theControl program that prevents the

system from improper use and takessystem from improper use and takescare of error situationscare of error situations

A system software that acts as an intermediary between theA system software that acts as an intermediary between theuser and the computer and works asuser and the computer and works as


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Jobs of an O.S. : Providing UserJobs of an O.S. : Providing User

Interface Interface

Operating system provides these facilities for the user:Operating system provides these facilities for the user:

Program creation : editors, debuggers, otherProgram creation : editors, debuggers, otherdevelopment tools.development tools.

Program execution : load, files, IO operations.Program execution : load, files, IO operations. Access to IO devices: Read and writes.Access to IO devices: Read and writes.

Controlled access to files: protection mechanisms,Controlled access to files: protection mechanisms,abstraction of underlying device.abstraction of underlying device.

System access: Controls who can access theSystem access: Controls who can access thesystem.system.


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Jobs of an O.S. : As a ResourceJobs of an O.S. : As a Resource

Manager.Manager.

Processors : Allocation of processes to processors,Processors : Allocation of processes to processors,preemption, scheduling.preemption, scheduling.

Memory: Allocation of main memory.Memory: Allocation of main memory. IO devices : when to access io devices, which onesIO devices : when to access io devices, which ones

etc.etc. Files: Partitions, space allocation and maintenance.Files: Partitions, space allocation and maintenance.

Process : Applications, Data, objects.Process : Applications, Data, objects.


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Jobs of an O.S. : Providing ProtJobs of an O.S. : Providing Protectionection

and Security ..and Security .. When sharing resources, protection of the systems andWhen sharing resources, protection of the systems and

user resources from intentional as well as inadvertentuser resources from intentional as well as inadvertentmisuse.misuse.

Protection generally deals with access control. Ex:Protection generally deals with access control. Ex:Read only fileRead only file

Security deals usually with threats from outside theSecurity deals usually with threats from outside thesystem that affects the integrity and availability of thesystem that affects the integrity and availability of thesystem and information with the system.system and information with the system.

Example: username, password to access system. DataExample: username, password to access system. Dataencryption to protect information.encryption to protect information.


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Evolution of Operating SystemEvolution of Operating System

Serial ProcessingSerial Processing

Batch ProcessingBatch Processing

MultiprogrammingMultiprogramming

Time SharingTime Sharing

Parallel SystemParallel System

Distributed SystemDistributed System

Real Time SystemReal Time System


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Serial ProcessingSerial Processing

(Early 1950s)(Early 1950s)Typical setup:Typical setup:

Users would sign up for a time slot (e.g., 2am-3am) During that slot, had exclusive use of the computer

Must load program into memory space, overwriting old conten

Drawbacks:Drawbacks:

Inconvenient for user

Wasteful of computer time (computer was idle during setup,

debugging


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Batch ProcessingBatch Processing( Mid 1950s)( Mid 1950s)

Typical setup:Typical setup:

Users would submit jobs on

cards/tape to computer operator

Operator would combine multiple

jobs into a single batch job and load

into card/tape reader Each user job would be executed in

turn

Users received output after alljobs

finished

the primitive operating system incharge of executing the batch job was

called a resident monitor

it residedpermanently in memory

it monitoredthe execution of each job in

succession


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MultiprogrammingMultiprogramming(Early 1960s)(Early 1960s)

Typical setup:Typical setup:

Users submitted jobs to computer operatorJobs were loaded into separate memory partitionsComputer would begin executing first jobDuring idle period, could switch to another jobUser could receive output as soon as their job terminated


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Advantages:Advantages:

Interactive ness is restored.

CPU is kept busy.

Disadvantages:Disadvantages:

Hardware and O.S. required

become significantly more complex

Advantages and Drawbacks Advantages and Drawbacks


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Content of Primary Memory inContent of Primary Memory in

Single/Multi program systemsSingle/Multi program systems

OPERA

TING

SYSTEM

OPERA

TING

SYST

EM

UNUSED MEMORYUNUSED MEMORY

PROGRAM 1PROGRAM 1

TRADITIONAL SINGLE-TRADITIONAL SINGLE-PROGRAM SYSTEMPROGRAM SYSTEM

OPERA

TING

SYSTEM

OPERA

TING

SYST

EM

UNUSED MEMORYUNUSED MEMORY

PROGRAM 1PROGRAM 1

PROGRAM 2PROGRAM 2

PROGRAM 3PROGRAM 3

MULTIPROGRAMMINGMULTIPROGRAMMINGENVIRONMENTENVIRONMENT


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Typical setupTypical setup::

Many users share large capacity CPU: Time in CPU divided into slices ( e.g.,2 milliseconds) Each user has access to CPU during slice. If the job is not completed within the given time slice, it

is preempted and the next job gets the CPU. The preempted jobs gets the CPU back after all other

jobs get a chance to get the CPU

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Time SharingTime Sharing(Mid 1960s)(Mid 1960s)


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New computer architectures new demandsMultiprocessor Systems ( parallel systems or tightly

coupled systems) More than one processor in close communication, share

bus and clock, other resources Can increase throughput, save on shared resources, provide

greater reliability

Distributed systems ( loosely coupled systems)Distributed systems ( loosely coupled systems) Distribute the computation among several processors, each

with its own memory & resources Processors communicate via communications lines, e.g.,

high-speed buses or phone lines Similar benefits as multiprocessor, but generally simpler,

cheaper, more scaleable but slower.

New architectures (cont )


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New architectures (cont.)

Real-time systems

Some systems impose well-defined, fixed-time constraints

where large number of events external to the system arerequired to be taken care of.

e.g., control for scientific experiments, medical imaging

systems, industrial control systems.

Hard real-time: Critical tasks must be completed in specified time Secondary storage limited or absent, data stored in short term

memory or ROM Not compatible with timesharing

Soft real-time: Critical tasks are given priority over other tasks, but no

guarantees Limited utility in industrial control of robotics


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