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Języki Programowania

Podstawowe pojęcia

R. Pełka: Języki Programowania, 2008

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Plan wykładu

ƒ

Właściwości języków programowania

ƒ

Czytelność kodu

ƒ

Łatwość programowania

ƒ

Niezawodność

ƒ

Ewolucja języków programowania

ƒ

Język maszynowy

ƒ

Języki proceduralne

ƒ

Języki zorientowane obiektowo

ƒ

Rodzina języków programowania

ƒ

Popularność języków, trendy, zastosowania

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R. Pełka: Języki Programowania, 2008

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Języki …

Jezyk maszynowy

...01100100111011...

Jezyk maszynowy

...01100100111011...

Jezyk naturalny

...niech mi Pan nie przerywa, Panie...

Jezyk naturalny

...niech mi Pan nie przerywa, Panie...

Jezyk niskiego poziomu

Jezyk niskiego poziomu

Jezyk wysokiego poziomu

Jezyk wysokiego poziomu

Jezyk niskiego poziomu

Jezyk niskiego poziomu

Jezyk wysokiego poziomu

Jezyk wysokiego poziomu

R. Pełka: Języki Programowania, 2008

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Programowanie komputera

Sprzet

Jezyk maszynowy

Assembler

Jezyk wysokiego poziomu

Fortran

C, C++

Pascal

Kompilacja

Egzekwowanie
programu

Narzedzia programistyczne

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R. Pełka: Języki Programowania, 2008

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Dlaczego istnieje tyle PLs?

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Teoretycznie, wszystkie języki programo-
wania są sobie równoważne

ƒ

Kompilowane/interpretowane na język
wewnętrzny procesora (asembler)

ƒ

Dlaczego istnieje tyle języków naturalnych (NLs)?

ƒ

W praktyce, języki naturalne spełniają rozmaite zapotrzebowania
określone przez

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Różne kultury (różne obszary zastosowań)

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Różne środowiska zawodowe

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Różne sposoby postrzegania świata

R. Pełka: Języki Programowania, 2008

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Evolution of LPs

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000000100000000000000000010000000000101110011100110110100001110011011101000111

001001110100011000010110001000000000001011100111010001100101011110000111010000

000000001011100111001001101111011001000110000101110100011000010000000000101110

011100110111100101101101011101000110000101100010000000000010111001110011011101

000111001001110100011000010110001000000000001011100111001001100101011011000110

000100101110011101000110010101111000011101000000000000101110011000110110111101

101101011011010110010101101110011101000000000000000000000000000000000010011101

111000111011111110010000000100110000000000000000000000001001000000010010011000

000000000000010101000000000000000000000000100100100001001010100000000000000100

000000000000000000000000000000000001000000000000000000000000101000000001000000

000000000010001001000000010000000000000001000000010101000000000000000000000000

100100100001001010100000000000000100000000000000000000000000000000000001000000

000000000000000000101100000001000000000000000100001000000000000000000000100000

000100000000000000000000000010000001110001111110000000001000100000011110100000

000000000000000000000000000000000000000000000001001000011001010110110001101100

011011110111011101101111011100100110110001100100001000010000000000000000000000

000000000000000000000000000000000000000001000000000000000000000000000000000000

000000000000000000000000000000000100000000001111111111110001000000000000000000

000000000000010000000000000000000000000000000000000000000000000000000000000000

000001000000000011111111111100010000000000000000000000000000000000000000000000

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000000000000000100000000000000000000000000001101000000000000000000000000000000

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000000000000001101000011001010110110001101100011011110010111001100011011100000

first computers

(e.g., ENIAC) were not

programmable

ƒ

had to be

rewired/reconfigured

for different

computations

late 40’s / early 50’s:

coded directly in machine

language

ƒ

extremely tedious

and error prone

ƒ

machine specific

ƒ

used numeric codes,

absolute

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R. Pełka: Języki Programowania, 2008

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Evolution of LPs

(cont.)

.file "hello.cpp"

gcc2_compiled.:

.global _Q_qtod

.section ".rodata"

.align 8

.LLC0: .asciz

"Hello world!"

.section ".text"

.align 4

.global main

.type main,#function

.proc 04

main: !#PROLOGUE# 0

save %sp,-112,%sp

!#PROLOGUE# 1

sethi %hi(cout),%o1

or %o1,%lo(cout),%o0

sethi %hi(.LLC0),%o2

or %o2,%lo(.LLC0),%o1

call __ls__7ostreamPCc,0

nop

mov %o0,%l0

mov %l0,%o0

sethi %hi(endl__FR7ostream),%o2

or %o2,%lo(endl__FR7ostream),%o1

call __ls__7ostreamPFR7ostream_R7ostream,0

nop

mid 1950’s: assembly languages
developed

ƒ

mnemonic names replaced
numeric codes

ƒ

relative addressing via names
and labels

a separate program (assembler)
translated from assembly code to
machine code

• still machine specific, low-level

R. Pełka: Języki Programowania, 2008

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Evolution of programming

(cont.)

late 1950’s: high-level languages developed

ƒ

allowed user to program at higher level
of abstraction

however, bridging the gap to low-level
hardware was more difficult

• a

compiler

translates code all at once

into machine code (e.g., FORTRAN,
C++)

• an

interpreter

simulates execution of the

code line-by-line (e.g., BASIC, Scheme)

Java utilizes a hybrid scheme

• source code is compiled into byte code
• the byte code is then interpreted by the

Java Virtual Machine (JVM) that is built
into the JDK or a Web browser

// File: hello.cpp

// Author: Dave Reed

//

// This program prints "Hello world!"

////////////////////////////////////////

#include <iostream>

using namespace std;

int main()

{

cout << "Hello world!" << endl;

return 0;

}

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R. Pełka: Języki Programowania, 2008

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FORTRAN (Formula Translator)

FORTRAN

was the first high-level

language

ƒ

developed by

John Backus

at IBM

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designed for the IBM 704 computer,
all control structures corresponded
to 704 machine instructions

ƒ

704 compiler completed in 1957

ƒ

despite some early problems,
FORTRAN was immensely popular –
adopted universally in 50's & 60's

ƒ

FORTRAN evolved based on
experience and new programming
features

• FORTRAN II (1958)
• FORTRAN IV (1962)
• FORTRAN 77 (1977)
• FORTRAN 90 (1990)

C

C FORTRAN program

C Prints "Hello world" 10 times

C

PROGRAM HELLO

DO 10, I=1,10

PRINT *,'Hello world'

10 CONTINUE

STOP

END

John Backus

R. Pełka: Języki Programowania, 2008

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ALGOL (Algorithmic Language)

comment ALGOL 60 PROGRAM

displays "Hello world" 10 times;

begin

integer counter;

for counter := 1 step 1 until 10 do

begin

printstring(Hello world");

end

end

ALGOL

was an international effort to

design a universal language

ƒ

developed by joint committee of ACM
and GAMM (German equivalent)

ƒ

influenced by FORTRAN, but more
flexible & powerful, not machine specific

ƒ

ALGOL introduced and formalized many
common language features of today

• data type
• compound statements
• natural control structures
• parameter passing modes
• recursive routines
• BNF for syntax (Backus & Naur)

ƒ

ALGOL evolved (58, 60, 68), but not
widely adopted as a programming
language

• instead, accepted as a reference language

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R. Pełka: Języki Programowania, 2008

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C Æ C++ Æ Java Æ JavaScript

ƒ

C (1971, Dennis Ritchie at Bell Labs)

• designed for system programming (used

to implement UNIX)

• provided high-level constructs and low-

level machine access

ƒ

C++ (1985, Bjarne Stroustrup at Bell Labs)

• extended C to include objects
• allowed for object-oriented

programming, with most of the efficiency

of C

ƒ

Java (1993, Sun Microsystems)

• based on C++, but simpler & more

reliable

• purely object-oriented, with better

support for abstraction and networking

ƒ

JavaScript (1995, Netscape)

• Web scripting language

#include <stdio.h>

main() {

for(int i = 0; i < 10; i++) {

printf ("Hello World!\n");

}

}

#include <iostream>

using namespace std;

int main() {

for(int i = 0; i < 10; i++) {

cout << "Hello World!" << endl;

}

return 0;

}

public class HelloWorld {

public static void main (String args[]) {

for(int i = 0; i < 10; i++) {

System.out.println("Hello World ");

}

}

}

<html>

<body>

<script type="text/javascript">

for(i = 0; i < 10; i++) {

document.write("Hello World<br

/>");

}

</script>

</body>

</html>

C

C++

Java

JavaScript

R. Pełka: Języki Programowania, 2008

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Other influential languages

ƒ COBOL

(1960, Dept of Defense/Grace Hopper)

ƒ

designed for business applications, features for structuring data & managing files

ƒ BASIC

(1964, Kemeny & Kurtz – Dartmouth)

ƒ

designed for beginners, unstructured but popular on microcomputers in 70's

ƒ Simula 67

(1967, Nygaard & Dahl – Norwegian Computing Center)

ƒ

designed for simulations, extended ALGOL to support classes/objects

ƒ Pascal

(1971, Wirth – Stanford)

ƒ

designed as a teaching language but used extensively, emphasized structured
programming

ƒ Prolog

(1972, Colmerauer, Roussel – Aix-Marseille, Kowalski – Edinburgh)

ƒ

logic programming language, programs stated as collection of facts & rules

ƒ Ada

(1983, Dept of Defense)

ƒ

large & complex (but powerful) language, designed to be official govt. contract
language

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R. Pełka: Języki Programowania, 2008

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Nie ma idealnego rozwiązania …

ƒ

remember

: there is no best programming language

ƒ

each language has its own strengths and weaknesses

ƒ

languages for a specific application

business applications

Æ

COBOL

artificial intelligence

Æ

LISP/Scheme or Prolog

systems programming

Æ

C

software engineering

Æ

C++ or Java or Smalltalk

Web development

Æ

Java or JavaScript or VBScript or perl

R. Pełka: Języki Programowania, 2008

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The family of PL

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R. Pełka: Języki Programowania, 2008

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PL in common use

SourceForge

R. Pełka: Języki Programowania, 2008

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PL in coomon use

(cont.) - books

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R. Pełka: Języki Programowania, 2008

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Popularność cd.

R. Pełka: Języki Programowania, 2008

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Language speeds

www.bagley.org/~doug/shoutout

Completely Random and Arbitrary
Point System