Programming LanguagesThird Edition

Chapter 1 – Part 1The Origins of Programming Languages

First … a QUIZ !!!

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Computer Hardware Milestones

Predecessor of “modern day” computer?

• mid 1800’s – Analytical Engine designed by Charles Babbage – “Father of the computer”

• Analytical Engine Emulator

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First computer programmer?

• mid 1800’s – Augusta Ada Byron King, Countess of Lovelace, (aka Ada Lovelace)– daughter of poet Lord Byron– lifelong friend of Charles Babbage– wrote an algorithm for Analytical Engine

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First “modern day” computer? *

• Actually, lots of contenders, all circa 1940’s• Three important characteristics:

• electronic• general purpose• programmable

(note: no mention of “memory” or “storage”)

* From The Innovators, by Walter Isaacson

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First “modern day” computer?

• Mark-1 (used for calcs for atomic bomb in WWII)• Harvard, Navy, IBM• “programmed” by Grace Hopper (more later)• electromechanical, not completely electronic

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First computer bug!

First “modern day” computer?

• Colossus (UK for breaking German codes in WWII)• not to be confused with electromechanical machine Alan

Turing built to decode German Enigma codes in The Imitation Game

• binary, electronic, semi-programmable but not general-purpose

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First “modern day” computer?

• ENIAC (electronic numerical integrator and calculator)• electronic (vacuum tubes), programmable, general-

purpose• programmable by rewiring it – took forever!• fun fact: not binary but base 10• basis for subsequent computers!

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Note this woman in the picture

First commercial “personal computer”?

• 1970’s – Apple

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IBM PC introduced - Predecessor of today’s Windows machines?

• 1981

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Apple Macintosh introduced?

• 1984

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End of Quiz!

Next– A bit about computer architecture– Some history of programming language

development

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The First Stored Programs (EDVAC – Electronic Discrete Variable Automatic Calculator)

• John von Neumann

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CPU should be wired with small set of GENERALPURPOSE instructions

Memory would hold BOTH data and instructions

Machine Language

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BOTTOM LINE:

Machine language programmingwas tedious

and error prone !!!

“Real” Programmers

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Real Programmers Don't Write SpecsAlso see Real Men Don’t Eat Quiche https://en.wikipedia.org/wiki/Real_Men_Don%27t_Eat_Quiche

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Link to O’Reilly programming language poster

Assembly Language

• 1950’s• a set of mnemonic symbols for instruction codes

and memory locations

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This:

MOV EAX, VAR1ADD EAX, 25MOV VAR2, EAX

Sure beats this:

00110101 00010111 0000101010111101 00010111 0001100100110101 00010101 00010111

Assembly Language (cont’d.)

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So … Assembly Language is an improvement, but …

has some drawbacks:• Lacks abstraction

– Doesn’t look like conventional mathematical notation

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Y=X+3

• Lacks portability– Each type of computer hardware architecture has its

own machine language instruction set and requires its own dialect of assembly language

So … Assembly Language is an improvement, but …

has some drawbacks:

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So … Assembly Language is an improvement, but …

has some drawbacks:

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One assembly language

statement

ONEmachine language

statement=

Next Improvement:High-Level Languages!

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One high-level language

statement

MANYmachine language

statements=

High-Level Languages

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This:

VAR2 = VAR1 + 25

Beats This:

MOV EAX, VAR1ADD EAX, 25MOV VAR2, EAX

• higher level of abstraction

High-Level Languages

• Programs are more portable– Same program can be translated into the machine

code of many different computers by using different translator programs

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Some Legendary Languages

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FORTRAN and Algebraic Notation

• FORmula TRANslation language– Developed by John Backus in the early 1950s– Lacked the structured control statements and data

structures of later high-level languages– Designed with one computer in mind (IBM 704)

which dictated some of its syntax– Primary goals efficiency and acceptance– Popular with scientists and engineers for its support

for algebraic notation and floating-point numbers– Sample FORTRAN code :

http://en.wikibooks.org/wiki/Fortran/Fortran_examples

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The ALGOL Family

• ALGOrithmic Language released in 1960– Unlike FORTRAN, machine independent– Included structured control statements for

sequencing (begin-end blocks), loops (for loop), and selection (if and if-else statements)

– Supported different numeric types – Introduced the array structure– Supported procedures, including recursive

procedures– Sample ALGOL code:

http://en.wikipedia.org/wiki/ALGOL_60

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The ALGOL Family (cont’d.)

• ALGOL was the first language to receive a formal specification or definition– Included a BNF grammar that defined its features

for both programmers and for compiler writers• Large number of high-level languages descended

from ALGOL, including:– Pascal: language for teaching programming in the

1970s– Ada: for embedded applications of U.S. Dept. of

Defense

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COBOL• COmmon Business-Oriented Language

– Designed for “data processing” around 1960– Natural language readability– Machine-independent / portable– “record” data structure– File handling features– Required language on DOD computers at one time– Standardized– Grace Murray Hopper – key designer / legend– Sample COBOL code: http://people.sju.edu/~

jhodgson/cobol/sample.html– http://

www.zdnet.com/article/50-years-and-still-going-strong-will-we-ever-be-ready-to-kill-off-cobol/Programming Languages, Third Edition 29

C and C++

• C developed at Bell Telephone Labs in late 60’s – early 70’s– For systems programming– “high-level” replacement for assembly language –

sort of the “best of both worlds”– Although Unix operataing system originally written in

assembly language, was later written in C• C++ also developed at Bell Labs – late 70’s – 80’s

– Essentially C with object-oriented features (classes)

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BASIC

• Beginner’s All-purpose Symbolic Instruction Code– Developed in late 60’s – For time-sharing systems– For “beginners” – easy to learn– Interactive / Interpreted– Sample BASIC code:

http://en.wikipedia.org/wiki/BASIC

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Pascal• Developed by Nicklaus Wirth in late 1960’s

– Named for famous mathematician / philosopher Blaise Pascal

– Conceptually simpler successor to ALGOL 60– Popular as a teaching language in late 70’s - 80’s– Control structures reflect notion of “structured

programming” – algorithms only require 3 fundamental logic patterns• Sequence• Selection• Iteration (repetition or loops)

– Sample Pascal code: http://en.wikipedia.org/wiki/Turbo_Pascal

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Ada• Developed by DOD in late 70’s – early 80’s

– Named for Ada Lovelace (daughter of poet Lord Byron) – corresponded with Charles Babbage and wrote “programs” for his Analytical Engine and is known as “world’s first computer programmer”

– For “embedded systems” – computers built into other machines – previously programmed in assembly language

– Concurrency constructs– Sample Ada code:

http://sandbox.mc.edu/~bennet/ada/examples/f2_adb.html

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