CS 1313010Computer Programming

in Fortran 90& C

Instructor: Dr. Henry NeemanTAs: Ashwin Seshadri,Hisham Qureshi

Prerequisite:MATH 1523(ElementaryFunctions)or equivalent

ClassMeetings:Tues/Thurs10:30-11:45amGLCH 123Labsections:Fridays10:30am,1:30pm& 2:30pmCarson206

Note: this classis NOT for studentsmajoringin CSor enrolledin CSoptionprograms.

Announcements13January 2000

Office Hours� HenryNeeman

SarkeysEnergy Center1252Tuesdays& Thursdays12:15-1:15pm(right afterclass)

� HishamQureshiCarsonEngineeringCenterB8Mondays& Wednesdays10:00-11:30am

� AshwinSeshadriCarsonEngineeringCenterB18Mondays& Wednesdays3:00-4:30pm

A NoteAbout the Fortran 90Textbook

I spoke with Prof. LakshmivarahanTuesdayafternoon,andappar-ently the5th and6th editionsof Programming in Fortran 90/95 arebasicallythesamebook.King Kopy (Lindsey & Jenkins)hasthe6thedition,which youshouldbuy.

An ExcellentResource

C.-K. Shene’sFortran90Tutorial (linkedfrom theclasswebpage)http://www.cs.mtu.edu/shene/COURSES/cs201/NOTES/fortran.html

Outline of Fortran 90 Topics

� Overview of Computing� ComputerOrganization� Languages� ProblemSolving

� Variables� DataTypes� BasicDataTypes� 1D Arrays� DerivedDataTypes� Assignments

� Expressions� Numeric� Non-numeric

� ControlStructures� Branching� Repetition

� Procedures� Subroutines� Functions

� Modularity� Modules� InterfaceBlocks

� Input/Output� Formatting� Files

Note: this is roughly how thispartof thesemesterwill go.

What’ sAll This RAM/ROM Stuff?

Abbrev Name Read? Write? Addressing Volatile?

RAM RandomAccessMemory Yes Yes Arbitrary YesROM ReadOnly Memory Yes No Arbitrary No

In day-to-dayconversation,“RAM” meansthesamethingas“memory.”Both referto mainmemory.

CDROM

WhenaCD holdsdatainsteadof music,it actsverymuchlikeROM:� it canonly bereadfrom, but not written to;� it’s nonvolatile;� it canbeaddressedessentially arbitrarily.

Disadvantageof CDROM comparedto ROM:� slower (CDROM 7 MB/sec,ROM 100MB/sec)

Advantagesof CDROM comparedto ROM:� muchcheaper� canhavearbitraryamountof storage(onmany CDs)

Bits, Bytes,Words, etc

� Bit (BinarydigIT )� Tiniestpossiblepieceof memory� Possiblevalues:0 or 1, Falseor True,Off or On� Bits aren’t individually addressable: youcan’t reador write justone

bit to memory

� Byte: apackageof 8 bits (typically)� Onmostplatforms (kindsof computers),thesmallestaddressable

pieceof memory:youcanreador write anindividual byte� Possiblevalues:0..255,-128..127

Canalsorepresentacharacter(e.g.,letter, digit, punctuation)

� Word: apackageof 4 or 8 contiguousbytes(typically)� Onsomeplatforms(e.g.,CrayJ90),thesmallestpossibleaddressable

pieceof memory� Standardsizefor storinganumber(integeror real)

Putting Bits Together

��� �2 possiblevalues(0, 1)

� �4 possiblevalues(0, 1, 2, 3)

�� �8 possiblevalues(0, 1, 2, 3, 4, 5, 6, 7)

�� �16possiblevalues(0, 1, 2, 3, 4, 5, 6, 7, ... , 15)

...��� �

256possiblevalues(0, 1, 2, 3, ... , 255)

...� ��� �

1,024possiblevalues

...� ��� �

65,536possiblevalues

...� �� �

4,294,967,296values(typical sizeof anintegerin mostcomputerstoday)

Powersof 2

��� = 1��� = 2��� = 4��� = 8��� = 16��� = 32�� = 64�"! = 128��# = 256��$ = 512���%� = 1,024� �&� = 2,048� � � = 4,096��� � = 8,192� �'� = 16,384� � � = 32,768��� = 65,536���(! = 131,072� �%# = 262,144���%$ = 524,288��� � = 1,048,576

Kilo, Mega,Giga, Tera, Peta

Kilobyte: �)+* bytes , 1,024bytes - 1,000bytesApproximatesize:onee-mail(plain text)

DesktopExample:TRS-80w/4 KB RAM (1977)

Megabyte: /.0* bytes , 1,048,576bytes - 1,000,000bytesApproximatesize:30phonebookpages

DesktopExample:IBM PS/2PCw/1 MB RAM (1987)

Gigabyte: /10* bytes , 1,073,741,824bytes - 1,000,000,000bytesApproximatesize:15copiesof theOKC whitepages

Desktop:c. 1997

Terabyte: 324* bytes , 1,099,511,627,776bytes - 1,000,000,000,000bytesApproximatesize:5500copiesof aphonebooklisting everyonein theworld

Desktop:???

Petabyte: /50* bytes - 1,000,000,000,000,000bytesDesktop:???

Moore’sLaw: computingpowerandcapacitydoublesevery year

Actually, GordonMoore(ChairmanEmeritus,Intel Corp)observedin 1965the“doubling of transistordensityon amanufactureddie every year.” Usually, this ishedgedby sayingthatcomputingpowerdoublesevery18-24months.See:

http://developer.intel.com/update/archive/issue2/feature.htm

Programming LanguageHierar chy

� High Level Languages� Examples:Fortran,C, Java,HTML� Usuallyarestandardized,socanbeusedonany kind of com-

puter� Typically aredesignedfor aparticularkind of applicatione.g.,Fortranfor scientificapplications,C for operatingsys-temdesign,HTML for webpages,SASfor statistics

� AssemblyLanguage:specificto a particularCPUSetof simplecommands(e.g.,loada valuefrom a locationin memory;addtwo numbers;storea valueinto a locationin memory)

� MachineLanguage:binarycodethattheCPUunderstandsdirectly; binaryrepresentationof assemblylanguage

Converting BetweenLanguages

Compilers,interpretersandassemblersareprogramsthatturnprogramspeoplecanreadinto programscomputerscanrun.

Compiler� convertsa high level languagesourcecodeof a programinto a

machinelanguageexecutable� all at once� mustbecompletedbeforeexecutingtheprogram� Examples:Fortran,C

Interpreter� converts a high level languagesourcecodeinto machinelan-

guage� convertsandexecutesonestatementat a time� conversionandexecutionoccurwhile running� Examples:Perl,HTML, SAS,Mathematica

Assembler� convertsaCPU-specificassemblycodeinto machinelanguage� likea compiler, but low level

Our Old Friendhelloworld.f90

scarecrow 212% script helloworld.scriptScript started on Sat Jan 8 12:53:02 200scarecrow 1% cat helloworld.f90

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Program: helloworld !!!!!! Module: main !!!!!! Author: Henry Neeman 123-45-6789 !!!!!! Class: CS 1313 010 Spring 2000 !!!!!! Lab: Sec 013 Fridays 2:30pm !!!!!! Description: Prints the sentence !!!!!! ’Hello, world.’ to standard !!!!!! output. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!PROGRAM helloworld!! Declarations!! No implicitly typed variables.IMPLICIT NONE!! Execution!! Print the sentence to stdout.PRINT *, ’Hello, world!’

END PROGRAM helloworldscarecrow 2% f90 -o helloworld helloworld.f90scarecrow 3% helloworldHello, world!

scarecrow 4% ctrl-DScript done on Sat Jan 8 12:53:22 200scarecrow 213%

Executable: helloworld

Linker/Loader

helloworld.f90F90 Source Code:

Assembly Code: helloworld.s

Assembler

Object File: helloworld.o

Compilingf90 -o helloworld helloworld.f90

compilercalled by

Automatically

Compiler

Executable: helloworld

Linker/Loader

Lexical Analysis

Parsing

Semantic Analysis

Intermediate Code Generation

Optimization

Assembly Code Generation

helloworld.f90F90 Source Code:

Assembly Code: helloworld.s

Assembler

Object File: helloworld.o

Compiler Detailsf90 -o helloworld helloworld.f90

Com

pile

r

Elementsof a Compiler

Compiler� Lexical Analyzer:identifiesprogram’s“word” elements

� Comments(ignored)� Keywords (e.g.,PROGRAM, END)� Constants(e.g.,5, ’Hello, world!’, .TRUE.)� User-definedIdentifiers (e.g.,helloworld)� Operators; e.g.6 arithmetic:

+ - * / **6 relational:== /= < >=6 logical:.AND. .OR. .NOT.

� Parser:determinestheprogram’sgrammar� SemanticAnalyzer:determineswhattheprogramdoes� IntermediateCodeGenerator:expresses,as an assembly-like

program,whattheprogramdoes� Optimizer:makescodemoreefficient� AssemblyCodeGenerator:producesthe final assemblycode

thatrepresentswhattheprogramdoes

Assembler:convertsassemblycodeto machinecode

Linker/Loader:createsthefinal, executableversionof themachinecode

Assembly Code Generation

Lexical Analysis

Parsing

Semantic Analysis

Intermediate Code Generation

Compiling a Fortran 90 Statement

Load R00 from aLoad R01 from bR02 = R00 + R01

Store R02 into aplusb

ld r00,ald r01,b

ad r02,r00,r01st r02,aplusb

ASSIGN(VARIABLE[aplusb],ADDITION(VARIABLE[a],VARIABLE[b]))

ASSIGN

EXPRESSION

IDENTIFIER[aplusb] ASSIGN IDENTIFER[a] PLUS IDENTIFIER[b]

ADD

VARIABLEVARIABLE

VARIABLE

aplusb = a + b

AssemblyCodefor helloworld.f90on a DEC Alpha

ldah $gp, ($27)!gpdisp!1

unop

lda $gp, ($gp)!gpdisp!1

unop

ldq $27,

for_set_reentrancy($gp)!literal!2

lda $sp, -96($sp)

stq $26, ($sp)

ldq $16, $$5($gp)!literal!3

jsr $26, ($27),

for_set_reentrancy!lituse_jsr!2

ldah $gp, ($26)!gpdisp!4

mov 12, $1

lda $gp, ($gp)!gpdisp!4

ldq $27,

for_write_seq_lis($gp)!literal!5

ldq $3, $$7($gp)!literal!6

ldah $18, 901($31)

stl $31, 8($sp)

stq $1, 72($sp)

lda $16, 8($sp)

stq $3, 80($sp)

mov -1, $17

ldq $19, $$3($gp)!literal!7

lda $18, -256($18)

lda $20, 72($sp)

jsr $26, ($27),

for_write_seq_lis!lituse_jsr!5

ldah $gp, ($26)!gpdisp!8

ldq $26, ($sp)

lda $gp, ($gp)!gpdisp!8

mov 1, $0

lda $sp, 96($sp)

ret ($26)

AssemblyCodefor helloworld.f90on a Pentium III

pushl %ebp

movl %esp,%ebp

subl $24,%esp

movl $.C1_283,%eax

movl %eax,(%esp)

call pghpf_init

movl $14,%eax

movl %eax,8(%esp)

movl $.C1_297,%edx

movl %edx,4(%esp)

movl $.C1_300,%ecx

movl %ecx,(%esp)

call pgf90io_src_info

movl $.C1_283,%edx

movl %edx,12(%esp)

movl %edx,8(%esp)

movl $pghpf_0_+8,%eax

movl %eax,4(%esp)

movl $.C1_301,%ecx

movl %ecx,(%esp)

call pgf90io_ldw_init

movl %eax,-4(%ebp)

movl $13,%eax

movl %eax,16(%esp)

movl $.C1_304,%ecx

movl %ecx,12(%esp)

movl $.C1_283,%edx

movl %edx,8(%esp)

movl $.C1_285,%eax

movl %eax,4(%esp)

movl $.C1_298,%ecx

movl %ecx,(%esp)

call pgf90io_ldw

movl %eax,-4(%ebp)

call pgf90io_ldw_end

movl %eax,-4(%ebp)

movl $.C1_283,%eax

movl %eax,(%esp)

call pgf90_exit

leave

ret

AssemblyCodefor helloworld.f90on a DEC AlphaUsingFortran 90

ldah $gp, ($27)!gpdisp!1

unop

lda $gp, ($gp)!gpdisp!1

unop

ldq $27,

for_set_reentrancy($gp)!literal!2

lda $sp, -96($sp)

stq $26, ($sp)

ldq $16, $$5($gp)!literal!3

jsr $26, ($27),

for_set_reentrancy!lituse_jsr!2

ldah $gp, ($26)!gpdisp!4

mov 12, $1 ================>>>

lda $gp, ($gp)!gpdisp!4

ldq $27,

for_write_seq_lis($gp)!literal!5

=============================>>>

ldq $3, $$7($gp)!literal!6

ldah $18, 901($31) ==========>>>

stl $31, 8($sp)

stq $1, 72($sp) ==========>>>

lda $16, 8($sp) ==========>>>

stq $3, 80($sp) ==========>>>

mov -1, $17 ==========>>>

ldq $19, $$3($gp)!literal!7

lda $18, -256($18) =========>>>

lda $20, 72($sp)

jsr $26, ($27),

for_write_seq_lis!lituse_jsr!5

ldah $gp, ($26)!gpdisp!8

ldq $26, ($sp)

lda $gp, ($gp)!gpdisp!8

mov 1, $0

lda $sp, 96($sp)

ret ($26)

AssemblyCodefor helloworld.f90on a DEC AlphaUsingFortran 95

ldah $gp, ($27)!gpdisp!1

unop

lda $gp, ($gp)!gpdisp!1

unop

ldq $27,

for_set_reentrancy($gp)!literal!2

lda $sp, -96($sp)

stq $26, ($sp)

ldq $16, $$5($gp)!literal!3

jsr $26, ($27),

for_set_reentrancy!lituse_jsr!2

ldah $gp, ($26)!gpdisp!4

ldah $18, 388($31)

Machine Codefor helloworld.f90

10111101010100010101011110101001

10111010101000010101101011101000

01110101010000101011010111010001

01010100101010101101010101011010

...

How to Program in Machine LanguageDir ectly

(1) Write assemblycodefor theprogramdirectly by hand.(2) For eachassemblylanguageopcode, look up theassociatedmachinecodebit pattern.(3) On thecomputerconsole,flip switchesto matchthemachinecode.(4) Pressthe“Run” button.

Actually, on moderncomputers,programmingin machinelanguagedirectly is justaboutimpossible.

Fun and easy!

ApplicationProblem

ApplicationProblem

Executable

ApplicationProblem

ExecutableProgramming in

High Level LanguageCompiling

ApplicationProblem

Programming inHigh Level Language

Why Not Do Everything in Assembly Language?

Executableonly for

Pentiums

Programming in

Assembly LanguagePentium

Programming inMachine Language

Why Not Do Everything in Machine Language?

Not nearly as tedious or error-prone!

Incredibly tedious and ridiculously error-prone!

forDEC Alpha

Compiling Executablefor

Alphas

forPentium

Compiling Executablefor

Pentiums

forSGI/MIPS

Compiling Executablefor

SGI/MIPS

Can’t be run on any other kind of computer.May be completely obsolete in a few years.

Run

Bugs?

Bugs?

Compile

Write Program

Choose Programming Language

Construct Algorithm

Debug

The Programming Process

Yes

Yes

No

No

Formulate Problem

Get an A/Impress Your Boss/Sell for Zillions!

What Is an Algorithm?

An algorithm is a step-by-stepmethodfor solving a well-definedproblemusingfinite resources(computingtimeandmemory).

Example: Eating a Bowl of Corn Flakes� Getbowl from cupboard� Getspoonfrom drawer� Getboxof cornflakesfrom pantry� Getjug of milk from refrigerator� Placebowl, spoon,cornflakesandmilk on table� Openbox of cornflakes� Pourcornflakesfrom box into bowl� Openjug of milk� Pourmilk from jug into bowl� Closejug of milk� Returnjug to refrigerator� Goto table� Pick upspoon� Repeatuntil bowl is emptyof cornflakes

� Usingspoon,pick up cornflakesandmilk from bowl� Putspoonwith cornflakesandmilk into mouth� Pull spoonfrom mouth,leaving cornflakesandmilk� Repeatuntil mouthfulis mush6 Chew� Swallow� Leavemessfor housematesto cleanup

An Exampleof the Programming Process

The Problem

I haveasavingsaccountthatgets5.25%interestayear(compoundedcontinuously)andhas 7 500in it.My officemateDanhasasavingsaccountthatgets5.35%interestayear(compoundedcontinuously)andhas 7 750in it.Eachof uswantsto know how muchinterestwe’ll earnin a year’stime.

The Algorithm8 9 : ;=

where:

?A@ � �CBEDCFHG��GIFJG��GKMLONQPKML ...?SR is theannualinterestrate?UT is thetime in years?WV is theprincipalin thebankat thestartof theyear?YX is theamountin thebankat theendof theyear

Note: youcanfind this formulain any calculusbook.

The Programming Language

Fortran90,of course!

Check Principal

Check Time

Input Principal

Input Rate

Check Rate

Input Time

Compound Interest Algorithm in Detail

Output Amount

Compute Amount

CodeDevelopmentPart 1

% cat interest.f90PROGRAM interestIMPLICIT NONEREAL :: principal, rate, time, amountPRINT *, ’This program computes continuously compounded interest.’PRINT *, ’What is the principal, in dollars?’READ *, principalIF (principal < 0.0) THENPRINT *, ’Error: the principal ’, principal, ’ is negative.’STOP

END IFPRINT *, ’What is the interest rate, in percent?’READ *, rateIF (rate

CodeDevelopmentPart 2

% cat interest.f90PROGRAM interestIMPLICIT NONEREAL :: principal, rate, time, amountPRINT *, ’This program computes continuously compounded interest.’PRINT *, ’What is the principal, in dollars?’READ *, principalIF (principal < 0.0) THENPRINT *, ’Error: the principal ’, principal, ’ is negative.’STOP

END IFPRINT *, ’What is the interest rate, in percent?’READ *, rateIF (rate

CodeDevelopmentPart 3

% cat interest.f90PROGRAM interestIMPLICIT NONEREAL :: principal, rate, time, amountPRINT *, ’This program computes continuously compounded interest.’PRINT *, ’What is the principal, in dollars?’READ *, principalIF (principal < 0.0) THEN

PRINT *, ’Error: the principal ’, principal, ’ is negative.’STOP

END IFPRINT *, ’What is the interest rate, in percent?’READ *, rateIF (rate

% interestThis program computes continuously compounded interest.What is the principal, in dollars?750What is the interest rate, in percent?5.35What is the time of compounding, in years?1After 1.000000 year(s) of compoundingat 5.350000 percent interest a yearon a principal of 750.0000 dollarsthe amount is 791.2178 dollars.

The Program for Project #1

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Project #1: Thinking of a Number !!!!!! Program: mynumber !!!!!! Module: main !!!!!! Author: Henry Neeman 123-45-6789 !!!!!! Class: CS 1313 010 Computer Programming, Spring 2000 !!!!!! Lab: Sec 013 Fridays 2:30pm !!!!!! Description: Asks the user to pick a number within a !!!!!! range, then tells whether the user"s number matches the !!!!!! program"s. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!PROGRAM mynumber

!! Declarations!! No implicitly typed variables.IMPLICIT NONE! Parameter constants! minnum: the user"s number should be at least this.! minnum: the user"s number should be at most this.! mynum: the number that the computer is "thinking" of.INTEGER,PARAMETER :: minnum = 1, maxnum = 10INTEGER,PARAMETER :: mynum = 5! Local variable! yournum: the user"s chosen number.INTEGER :: yournum!! Execution!! Tell the user the range to choose from.PRINT *, "I’m thinking of a number between ", &minnum, " and ", maxnum, "."

! Ask for the user"s number.PRINT *, "What number am I thinking of?"! Input the user"s number.READ *, yournum! Check whether the number is correct.IF ((yournum < minnum) .OR. (yournum > maxnum)) THEN! Idiotproofing: if it"s outside the range, complain.PRINT *, "Hey! That’s not between ", &

minnum, " and ", maxnum, "!"ELSE IF (yournum == mynum) THEN! If it"s correct, be amazed.PRINT *, "That’s amazing!"

ELSE IF (ABS(yournum - mynum) == 1) THEN! If they"re within 1, say they"re close.PRINT *, "Close, but no cigar; I had ", mynum, "."

ELSE! Otherwise, be cruel.PRINT *, "Bzzzt! My number was ", mynum, "."

ENDIFEND PROGRAM mynumber

Typical Project #1Operation

scarecrow 2% f90 -o mynumber mynumber.f90Linking:scarecrow 3% mynumberI’m thinking of a number between 1 and 10.What number am I thinking of?0Hey! That’s not between 1 and 10!

scarecrow 4% mynumberI’m thinking of a number between 1 and 10.What number am I thinking of?2Bzzzt! My number was 5.

scarecrow 5% mynumberI’m thinking of a number between 1 and 10.What number am I thinking of?4Close, but no cigar; I had 5.

scarecrow 6% mynumberI’m thinking of a number between 1 and 10.What number am I thinking of?5That’s amazing!

scarecrow 7%

Pick 2

1. Takeoutablanksheetof notebookpaper.2. At thetop,write:

(a) Name& studentID(b) Class& semester(CS1313ComputerProgramming,

Spring2000)(c) Labsection,day& time

3. Directly below, write thenumber1.4. Abouthalfwaydown thepage,write thenumber2.5. For eachnumber, write anissuethatyou’d likeexpandedonor

clarified. It doesnothave to besomethingwe’vecoveredinclassyet,but it shouldbedirectly relatedto computing.