The History & Evolution of Computer Programming

…and an analysis of basic programming (v 0.102.232)

Programs are Everywhere! Your computer Your cellphone Your microwave Your toaster

At some level, almost all electronic devices have some type of programming that tell the different components how to interact with one another.

A History of Programming:Before 1940 The “first” program actually

predates the first modern computerThe Jacquard Loom, in 1801, used

holes punched in cards to represent the movement of the sewing loom arms.

Ada Lovelace, in 1843, while translating Luigi Menabrea’s memoirs on Charles Babbage’s Analytical Engine, added a series of notes which detailed a method of calculating Bernoulli numbers with the Analytical Engine.

The first real program written for a real computer is credited to Grace Hopper, written for the Harvard Mark I computer in 1944.

A History of Programming:Before 1940 Charles Babbage (1791 – 1871)

English mathematician, philosopher, inventor, and mechanical engineer○ First to originate the concept of a

programmable computer.○ Sought a method to calculate

mathematical tables mechanically to remove the high rate of human error.

○ Conceived of and designed the DifferenceEngine, then the Analytical Engine. Neither were actually created in his lifetime.

○ A Difference Engine was built based upon his work, in 1991. On display in the London Science Museum.

A History of Programming:Before 1940 Ada Lovelace (1815 – 1852)

The “first” programmer○ The only legitimate child of

poet Lord Byron.○ Primary claim to fame is having

written a description of CharlesBabbage’s Analytical Engine.

○ The programming language, Ada,created for the United States Department of Defense, was named in her honor.

A History of Programming:Before 1940 Alan Turing (1912 – 1954)

English mathematician, logician, cryptanalyst, and computer scientist.○ One of the fathers of computer science.○ Provided a formalization of the concept

of the algorithm and computation with the Turing machine.

○ Came up with the “Turing Test”, a proposal for a test of artificial intelligence in machines.

A History of Programming:Before 1940 Herman Hollerith (1860 – 1929)

German-American statistician○ Developed a mechanical tabulator to

rapidly tabulate data from millions of punch cards.

○ His electric tabulating system was usedto tabulate the 1890 census in only oneyear.

○ His firm, along with four other companies, merged to form the Computing Tabulating Recording Corporation, which was later renamed to International Business Machines (IBM)

A History of Programming:The 1940s The 1940s saw the rise of the first

recognizably modern, electrically powered computers.These early computers required hand tuned

assembly language programs to run.○ The ENIAC (Electronic Numerical Integrator And

Computer) was the first general-purpose electronic computer, in 1946.

Important languages developed at this time:○ Plankalkül (1943)○ ENIAC coding system (1943)○ C-10 (1949)

Types of Programming Languages Programming languages can be broken

down into three general types:Machine language is a set of instructions and

data directly read by a CPU. High and low level languages are interpreted into machine language for computers to read.

Low-level languages offer little or no abstraction from a computer’s instruction set architecture.

High-level languages offer strong abstraction from the details of the computer, some even including natural language elements. Meant to be more user-friendly and easier to use.

A History of Programming:The 1950s & 60s The 1950s saw the rise of the first modern

programming languages, many of whose descendants are still used today.

The mid-50s saw the publication of the ALGOL 60 Report, which consolidated all the programming ideas circulating at the time, and introduced two key language concepts:nested block structurelexical scoping

A History of Programming:The 1950s & 60s Backus-Naur Form (BNF)

A mathematically exact notation for language syntax that was introduced in the late 50s.

<postal-address> ::= <name-part> <street-address> <zip-part>

<name-part> ::= <personal-part> <last-name> <opt-jr-part> <EOL> | <personal-part> <name-part>

<personal-part> ::= <first-name> | <initial> "."

<street-address> ::= <house-num> <street-name> <opt-apt-num> <EOL>

<zip-part> ::= <town-name> "," <state-code> <ZIP-code> <EOL>

<opt-jr-part> ::= "Sr." | "Jr." | <roman-numeral> | ""

A History of ProgrammingThe 1950s & 60s ALGOL 68 was a further attempt to redefine

programming languages, but was deemed too difficult. Attempts to simplify it resulted in the Pascal language.

Other important languages developed in this time: FORTRAN (FORmula TRANslator) (1954) LISP (the LISt Processor) (1958) COBOL (COmmon Business Oriented Language) (1959) Simula (1962) BASIC (Beginner’s All-purpose Symbolic Instruction

Code) (1964)

Programming Paradigms Programming paradigms are the fundamental

styles used in programming.Paradigms differ in the concepts and abstractions

used to represent elements of a program and steps that compose a computation.○ COBOL and FORTRAN among others, are procedural

languages, meaning the programs are built from various functions or subroutines. These type of languages use vocabulary relative to the problem being solved.

○ The opposite of procedural programming is declarative programming, where the computer is told what the problem is, not how to solve a problem. Logic-based programming languages like Prolog are declarative in nature.

Programming Paradigms

More programming paradigmsImperative programming deal with

statements that alter a program state.In object-oriented programming, data and

methods of manipulating the data, are kept as a single unit called an object. This prevents the data from being manipulated by anything other than the object’s methods.

A History of ProgrammingThe 1950s & 60s Grace Hopper (1906 – 1992)

American computer scientist and US Naval Officer○ One of the first programmers for the Harvard

Mark I computer○ Developed the first compiler for a programming

language○ Conceptualized and developed COBOL, one of

the first modern programming languages.○ Popularized the term “debugging”, after removing

an actual moth from a computer.○ Referred to as “Amazing Grace” in the Navy.○ The U.S. Naval Destroyer USS Hopper is named

for her.

A History of Programming:The Late 60s & 70s New programming languages began to bloom

in the late 60s, introducing even more new languages:Pascal (1970)C (1972)Smalltalk (1972)Prolog (1972)ML (1973)SQL (1978)

This time saw the introduction and debate of “structured programming”, which basically meant programming without the use of the GOTO statement.

A History of Programming:The 1980s Increased focus on programming for large-

scale system through use of modulesThe languages Modula, Ada, and ML all

developed notable module systems in the 80s.

The 80s saw the movement towards RISC design in CPUsThis basically meant that hardware should be

designed for compilers rather than for assembly programmers.

A History of Programming:The 1980s Important languages developed in the

1980s included:Ada (1983)C++ (1983)Eiffel (1985)Erlang (1986)Perl (1987)

A History of Programming:The 1990s and Beyond The 90s saw the rise of RAD (Rapid

Application Development) languagesRAD languages usually included an IDE,

garbage collection, and were usually descended from older languages.○ Examples of RAD languages

Object PascalVisual Basic (1991)C# (2000)

A History of Programming:The 1990s and Beyond Important languages developed in this

time:Haskell (1990)Python (1991)Java (1991)Ruby (1993)Lua (1993)JavaScript (1995)PHP (1995)C# (2000)

A History of Programming:The 1990s and Beyond The 90s also saw the rising popularity of

scripting languages.Scripting languages allow control of one or more

software applications.○ “Scripts” are distinct from the core code of the main

application, and can often be created or modified by the end-user.

○ Scripting languages, unlike other high-level programming languages, do not need to be compiled.

○ Also referred to as “batch languages” or “job control languages”.

○ Modern web browsers are a good example. For example, Firefox is written in C/C++, and can be controlled

via JavaScript and/or PHP.

2000 and Beyond The evolution continues! Several new

trends in this decade include:Metaprogramming

○ This is writing of programs that write or manipulate other programs (or themselves) as their data

Integration with relational databases and/or XML

XML (Extensible Markup Language)More mainstream support for Unicode vs.

the ASCII character set

Analysis of a Program

Analysis of a Program Functions

At their most basic, programs are simply functions, or a collection of various variable assignments and executions of simple math-type statements.

Example:○ void main()

{ print “Hello, world”;}

○ This is a simple “Hello world” program, that simply prints the message “Hello, world” to the screen.

Analysis of a Program Relational Operators

AND is expressed in most languages as &&, also called “logical conjunction”

OR is expressed in most languages as ||, also called “logical disjunction”

“=“ refers to assigning a value, while “==“ tests for equality.○ In some languages, “===“ signifies a test for

equality in both value and data type.“!=“ or “<>” means not equal, and most other

numerical relational operators apply○ For example, “<“, “>”, “>=“, “<=“ all mean the same

thing in programming as they do in mathematics.

Analysis of a Program

Control FlowThere are various statements used in

programs to control how the flow through a program is executed, known as control flow statements○ Most programs need keywords to indicate the

type of control structure in use, to group various statements togetherbegin … end{ }indentation levels

Analysis of a Program Control Flow continued

Loops○ Loops are sequences of statements specified

once, but carried out several times in succession.A loop that calls itself in the course of its execution is

said to be recursive. Poorly written recursive loops can lead to infinite loops, which are bad (usually).

A simple recursive function: factorialsfunction factorial is:input: integer n such that n >= 0output: [n × (n-1) × (n-2) × … × 1]

1. if n is 0, return 1 2. otherwise, return [ n × factorial(n-1) ]

end factorial

Analysis of a Program Types of loops:

Count controlled loops○ Execute x amount of times before proceeding○ Most of these use a loop counter to keep track

of the number of times the loop has been executed

○ for loops most common typeCondition controlled loops

○ These types of loops repeat until a certain predefined condition has changed

○ Examples: while loops, do-while loops

Analysis of a Program

Types of loopsCollection-controlled loops

○ Some languages have constructs which allow looping through all elements of an array, or all members of a set or collection

○ Examples: foreach loopsSome languages allow for non-local control

flow in the form of conditions and exceptions.

Analysis of a Program Conditional statements

Conditional statements perform specific actions and computations depending on whether or not a specified Boolean condition evaluates to TRUE or FALSE.

If-Then-Else○ One of the most common conditional statements.

While the syntax can vary from one language to the next, the basic structure remains the same

○ if (condition) then(statements)

else(statements)

end if

Analysis of a Program

Conditional statementsElse If is an addition to If-Then-Else

statements, allowing multiple conditions to be tested at once

Ternary operators work similar to If-Then-Else statements, but in a shorthand kind of form○ (condition) ? (TRUE statement) : (FALSE

statement)

Analysis of a Program

Conditional statementsCase/Switch statements compare a given

value with specified constants and take action according to the first match○ switch (someCharacter)

{ case ‘a’: performActionA; break; case ‘b’: performActionB; break; case ‘c’: break; default : performActionC; break;}

Analysis of a Program Data Types

Many different types of data can be manipulated in programming

The data types provided are referred to as “primitive data types”, meaning they’re defined and provided by the programming language itself, as opposed to user defined data types.○ Integers○ Floating point (decimal values)

Floating point calculations in programming can be rather resource-intensive in some cases.

○ Char (single characters)

Analysis of a Program

Data Types continuedEven more data types

○ In some languages, a Boolean data type exists. Usually, it just an integer with a value of either 0 or 1.

○ StringsIn some languages, strings can be treated as

character arrays, and manipulated like arrays.In others, strings have special library-defined

functions for handling them.

Analysis of a Program

Data types continuedEven MORE data types…

○ Arrays are sets of values in a program that can be selected by indicesExample: foo = (0, 2, 3, 4, 5, 2, 10);

print foo[1];Would yield the result of “2”.

When working with arrays, it’s important to remember that counting begins with “0” in most languages.

Putting It All Together

A simple program that prints out the numbers from 1 to 10

void main(){ int x; for(x = 1; x < 11; x++) print x + “\n”; return;}

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New York, NY: ACM Press.  Koffman, Elliot B. & Friedman, Frank L. (1993). Fortran With Engineering Applications:

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Program?." History Fact Finder. Ed. Julie L. Carnagie. UXL-GALE, 2001.eNotes.com. 2006. 6 Dec, 2009 <http://www.enotes.com/history-fact-finder/science-invention/who-wrote-first-computer-program>