A Brief Introduction to the History of Computing - 4 ANU Faculty of Engineering and IT Department of...

A Brief Introduction to theHistory of Computing - 4

ANU Faculty of Engineering and ITDepartment of Computer Science

COMP1200 Perspectives on Computing

Chris Johnson April/May 2003

Intro to History of Computing 4: programming languages 2

History of Computing 4

1. History of the computer market:into the 4th generation

2. Generations of programming languages

3. High level languages

4. Computing history heroes:the Turing Awards


1. 4th generation market: 1981-

1981 IBM PC – a 16 bit personal computer for office desktops;command line operating system MS-DOS. “Word processing” becomes a software application for PC not a dedicated box

DOS:A\ dir *.*


1. 4th generation market: 1981- productivity software: word processor, spreadsheet, paint

and draw 1984 Apple Macintosh WIMP 1985 Microsoft Windows for PC applications become centred on

Graphical User Interface,push use of memory and processor speed enormously

FileOpenPrintClose


1. the 4th generation...

2003 common families of processor chips drive nearly all large and small computers

computer networks are as important as computers


1. 4th generation market: 1981 – mainframes, personal computers

mainframes continue as main computers – re-invented as servers to enterprise networks of personal workstations and PCs

mid 1980s: local computer networks transform the personal computer to the enterprise network; the Internet for email

mid 1990s: the World Wide Web on the Internet transforms the desktop PC from a tool for local processing and information management into a communication tool


1. 4th generation market: manufacturers

The biggest manufacturers of servers, workstations, desktops, laptops: market is fragmented, volatile, year by year

Compaq (includes DEC) [1 million servers; 14 million PCs worldwide; 12% of Australian PC market]

Dell [700k servers; 11% Australian PC market] IBM [660,000 servers] Hewlett-Packard [10%] now merged Compaq 2002 Sun [360,000 workstations; 9% Australian PC market] Apple [4% of Australian PC market] NEC [6 million PCs world] many other small companies: 48% Australian PC market, 25%

servers, 80 million PCs 2001 figures from Gartner Group press release web pages

The software market is now the big money– Microsoft, Oracle.


1. the market: from 1970...

mainframes: IBM and the BUNCH (approx 1968) IBM Burroughs->Sperry Rand/Unisys UNIVAC -------------------/ NCR Control Data Corporation CDC - supercomputers Honeywell

a few in UK (ICL), France (Bull), Germany (Siemens)

the minis (approx 1970) DEC Digital Equipment Corporation Data General Varian Hewlett-Packard... and others

the micros Apple (and Apricot and Acorn and...) Xerox Commodore ... many others


1. the market: from 1970 to 2001computers a commodity: fragmented,volatile

Compaq (includes DEC & H-P)[1 million servers; 14 million PCs worldwide; 12% of Australian PC market]

Dell [700,000 servers] IBM [660,000 servers] Sun [360,000 workstations, servers] Apple [4% of Australian PC market] NEC [6 million PCs world] many other small companies:

48% Australian PC market, 25% servers,80 million PCs

2001 figures from Gartner Group press release web pages


2. Programming languages don’t forget the software!

the history of computing includes softwarejust as much as hardware

software is applications operating systems and environments utilities: compilers, editors...

all created by human effortas collections of related programs using programming languages


2. The Generations of programming languages

[from Brookshear Figure 5.1]

“Generations” of languages relate to the degree of problem- or human- orientation vs machine orientation.These generations are not the same asthe generations of computer architecture.


2. Language generations 1,2,3

1. machine languages2. assembly languages3. high level languages

FORTRAN, COBOL, ALGOL, LISP

the biggest differences are in execution control structures,

(program control, flow control) data control modularity


2. Generations ofprogramming languages -& computers

programming languages1. machine lang 19452. assembly lang 19513. high level lang 1954

60s

4. 4GLs 70s5. AI based 80s6. network-aware 90s

computer architectures

1. valves1945

2. transistors 19593. Integrated 1964

Circuits4. PCs 1981

many high level

languages of different

types


3. High level languages: the evolution of types of language

[Brookshear Figure 5.2] plus S67 & Eiffel

Simula-67 Eiffel


3. High level languages: a family tree

[from Eric Levenez]

LISP

ALGOL

FORTRAN

COBOL

C

APL

AdaPascal

Modula


4. History of high level PLs: the elements of high level PLs

data control definition: naming and types storage life structure manipulation (arithmetic)

Object-Oriented languages Simula 67 C++ Smalltalk Eiffel 1985 Java 1995 C#

} program modularity

program execution control jumps, conditions, loops,

subroutine calls

abstraction subroutines nesting classes & inheritance


4. Aspects of high level programming languages (1) program (execution) control

how the point of execution moves through the parts of the program

examples in Eiffel: if-statement, loop, function call

data control names of variables have a limited lifetime during

execution names have restricted visibility (scope) in parts of

the program examples in Eiffel:

function local variable, object feature variable


4. data control and program control - an Eiffel program from earlierclass BDMcreation doit -- read a given number of ints, find min and maxfeature doit is

local count, max, min: INTEGER

doio.read_integer; count := io.last_integer -- omit promptsio.read_integer; max := io.last_integer; min := max

from i:=1until i=countloop

io.read_integer;if max < io.last_integer then max := io.last_integer endif min > io.last_integer then min := io.last_integer endi:=i+1

endio.put_string("The largest number was: "); io.put_integer(max)io.put_string(" and the smallest was: "); io.put_integer(min)

endend -- class BDM

data control:the scope ofcount, max, min

data control:the scope of i


4. data control and program control: machine language (g1) add two numbers - see Brookshear p. 208

156C166D5056306EC000

Extending this "language" from a sequence of numbers to include comments makes life easier for the original programmer - and for the next programmer to read it.

;add Price (6C) and ShippingCost (6D), Total to 6E156C ;load 6C to R5166D ;load 6D to R65056 ;add them, result to R0306E ;store R0 to 6EC000 ;stop here


4. data control and program control: assembly language (g2)

; data storage address definitions (these generate no instructions).DEF Price 6C.DEF Shipping 6D.DEF TotalCost 6E

; The actual instructions of the program; correspond exactly to the machine instructions above

; Add Price and Shipping to calculate TotalCost

LD R5, PriceLD R6, ShippingADD R0, R5, R6ST R0, TotalCostHLT

[adapted from Brookshear p.208]


4. control flow in assembly language; pricing variables

- now with automatic layout in memoryPrice: .SZ 1

Shipping: .SZ 1TotalCost: .SZ 1

; if Shipping cost is greater than zero then; add Price and Shipping to calculate TotalCostLD R6, ShippingJZ R6, NoAddLD R5, PriceADD R0, R5, R6ST R0, TotalCostJMP Next

NoAdd: LD R6, Price ; else TotalCost equals PriceST R6, TotalCost

Next: HLT

Flow control is by test and jumps.

A loop is a jump back to anearlier point in the program


4. data control in assembly language; pricing variables

Price: .SZ 1Shipping: .SZ 1TotalCost: .SZ 1

; if Shipping cost is greater than zero then; add Price and Shipping to calculate TotalCostLD R6, ShippingJZ R6, NoAddLD R5, Price control flow ADD R0, R5, R6ST R0, TotalCostJMP Next

NoAdd: LD R6, Price ; else TotalCost equals PriceST R6, TotalCost

Next: HLT Assembly language provides no data control.These labels are all just addresses,data and program instructions mixed together


class BDMcreation doit -- read a given number of ints, find min and maxfeature doit is

local count, max, min: INTEGER

doio.read_integer; count := io.last_integer -- omit promptsio.read_integer; max := io.last_integer; min := max

from i:=1until i=countloop

io.read_integer;if max < io.last_integer then max := io.last_integer endif min > io.last_integer then min := io.last_integer endi:=i+1

endio.put_string("The largest number was: "); io.put_integer(max)io.put_string(" and the smallest was: "); io.put_integer(min)

endend -- class BDM

4. data and flow controlrecap


4. other aspects of high level programming languages syntax

description of the form of constructs in the language

semantics description of the meaning of constructs of the

language compilers and interpreters

the means of translating a high level language program to execution on a computer

run-time system utility support for all programs of the language

during execution in the computer

A Brief Introduction to the History of Computing - 4 ANU Faculty of Engineering and IT Department of...

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