1 © 2000-2002 John Urrutia. All rights reserved. Programming.

1© 2000-2002 John Urrutia. All rights reserved.

Programming


Topics

Programming in C

The make utility

Source Code Management


Programming in CWhy C?

Portable language

Easy access to system resources via system callsMemory Files

System FunctionsAvailable through a variety of libraries


Programming in CC Libraries

I/O

Mathematics

Graphics


Programming in CThe Process

AnalyzeUnderstand the problemCreate the problem algorithms

CodingTranslate problem into C language

CompilingTranslate C code into object code

LinkingLink edit object code into executable code


Programming in CAnalyze

thisWrite a program (DisplayIt) that will prompt the user for their name and then clear the terminal and write their name in the middle of the cleared terminal and display the prompt at the bottom of the terminal.


Programming in CAlgorithm

s1. Prompt the user for name.2. Clear the terminal.3. Write enough blank lines to

position to middle of screen.4. Write enough spaces to center

name5. Write name6. Write enough blank lines to

position to bottom.


Programming in CCoding

Parts of a C programComments – provide information

///*… … … … */

Declarations – state what is knownstring userName;

Functions – provide execution stepsvoid main()


Programming in CC statements

Data typesStandardUser defined

IdentifiersMust start with a letter or underscore

ExpressionsAny valid combination of operators &

operands


Programming in CC statements

Preprocessor directives

Identified by a # followed by a preprocessor keyword

Used to provide compiler access to system resources, macros and definitions#include <iostream>#define tabsize 4


Programming in CCodin

g//******************************************//* *//* *//* *//* *//* *//******************************************

This program will prompt the userfor their name and display it inthe center of the terminal screen

Flowerbox


Programming in CCodin

g#include <iostream>#include <iomanip>#include <string>#define lineWidth 80#define screenLength 24

Directives

using namespace std;

string getName(); FunctionalPrototype


Programming in C

1. Call the function that willPrompt the user for their name.

void main(){

int i;string userName;userName=getName();

2. Clear the terminal.system(“clear");

3. Write enough blank lines to position to middle of screen.for(i =1; i<screenLength/2; i++)

cout << endl;


Programming in C

4. Write enough spaces to center name

for(i =1; i<(lineWidth-userName.length())/2; i++) cout << " ";

5. Write the namecout << userName << endl;

6. Write enough blank lines to position to bottom.

for(i =1; i<screenLength/2; i++)cout << endl;

return;}


Programming in C

Read the users name from the standard input device

string getName(){

string temp; //Declare a holding areacout << “Enter your name \n”;cin >> temp; //Populate with namereturn temp; //Return name to caller

}


Programming in CCompilin

g Pre-processorInserts pre-coded files to match system hardware

Compiler

Assembler

Linkage Editor

Translates C Source code to Assembly language

Assembles Source code into Object code

Links Object code modules and libraries into an Executable binary file



g

Translate from source code

to object code

… Linux1]$ cc [-options] file-list [-larg ]Or

… Linux1]$ gcc [-options] file-list [-larg ]Or

… Linux1]$ g++ [-options] file-list [-larg ]



g

The CommonOptions

-c Compile only no link edit

-o Output file name-g Insert debug information-S Supress assembly and link-E Everything is supressed (pre-process only)


Programming in CLinking

Link object code

into executable code… Linux1]$ g++ -g DisplayIt.cpp -o /bin/DisplayIt


The make UtilityConstruction requires a specific order

to be followed. The House.1st build the foundation

2nd build the frame

3rd build interior

4th build trim.


The make UtilityIdentifies the dependencies in

constructing complex programs

Specifies the order of constructionIncludes compilation options

Includes object code (non-executable)

Includes binary code (executable)


The make Utility

The makefile fileTarget

The name of the file that is dependent on the pre-requisite list

Pre-requisite listThe list of files who must be present and

current for the target to be current.


The make Utility

The makefile fileConstruction commands

The commands to execute to produce the target.

Example follows:


The make Utility

num.h table.h

form.h

size.c length.c

size.o length.o

form

Text files

Headers

Source

Object

Executable


The make Utility

num.hnum.h table.htable.h

form.hform.h

size.c length.c

size.o length.o

form

Text files

Headers

Source

Object

Executable


The make UtilityThe makefile file

form: size.o length.og++ -o form size.o length.o

size.o: size.c form.hg++ -c size.c

length.o: length.c form.hg++ -c length.c

form.h: num.h table.hcat num.h table.h > form.h


The make Utility

size.csize.c length.clength.c

size.osize.o length.olength.o

form

Text files

Headers

Source

Object

Executable

num.h table.h

form.h


The make Utility

num.h table.h

form.h

size.c length.c

size.osize.o length.olength.o

formform

Text files

Headers

Source

Object

Executable


The make Utility make assumptions

.o – files have corresponding source filesThe source suffix will determine which

compile to invoke.

make is lazy it will only compile what it thinks is needed.Based on the timestamp of files


Debugging Programs

STOP!


Debugging ProgramsCompiler Warnings

Anything other than 0 errors/warnings is sloppy coding and potential bugs.

The insertion principle or cout is your friend.cout <<“*** I am about to enter***\n”;cout <<“*** I am about to exit***\n”; cout << “*** data value=“<<x<<‘\n’;


Debugging ProgramsSymbolic Debuggers allow you to:

Start your program, specifying anything that might affect its behavior.

Make your program stop on specified conditions.

Examine what has happened, when your program has stopped.

Change things in your program, so you can experiment with correcting the effects of one bug and go on to learn about another.


Debugging ProgramsDebugger and program execution

Programs must be compiled with the –g option for the debugger to use source code line numbers and variable definitions.

Programs are executed within a debugging session.


Debugger Executiongdb pgmname [core|PID]

Invokes the debugger and loads the binary file

Commandslist – displays 10 lines of source codebreak – set a stop point during executionrun – executes program until

breakpoint is reached


Debugger ExecutionCommands

print – displays the value of a variable at the breakpoint

bt – backtrace displays all of the entries in the execution stack.

up – moves your view of the program up one level in the

stack

down – moves your view of the program down one level in the

stack


Debugger ExecutionCommands

step – steps through one instruction

next – steps through to the nextinstruction of this

function

continue – continue execution

set – changes the value of a variable

call – invokes a program function


Debugger Example…]$ gbd –silent stars

(gdb) list 1,22 1 #include <iostream> 2 using namespace std; 3 int count=0; 4 int count2=1; 5 char star ='@'; 6 7 void printstars(int); 8 9 int main() 10 { 11 12 while (count< 1 || count > 23) 13 { 14 cout <<"enter a number from 1 through 23"<<endl;15 cin >> count; 16 cout << endl; 17 } 18 19 while (count2 < count) 20 { 21 printstars(count2); 22 count2++; (gbd)


Debugger Example

(gdb) list 19,40 19 while (count2 < count) 20 { 21 printstars(count2); 22 count2++; 23 } 24 25 while (count2 > 0) 26 { 27 printstars(count2); 28 count2--; 29 } 30 31 return 0; 32 } 33 34 void printstars(int num) 35 { 36 int x=0; 37 while (x < num) 38 { 39 cout << '*'; 40 x++; (gdb) breakpoint 21Breakpoint 1 at 0x8048774: file /home/user/C++Src/Stars.cpp, line 21.


Debugger Example(gdb) run

Starting program: /home/jurrutia/bin/Stars

enter a number from 1 through 23

5

Breakpoint 1, main () at /home/jurrutia/C++Src/Stars.cpp:21

warning: Source file is more recent than executable.

21 printstars(count2);

(gdb) print count $1 = 5 (gdb) print count2$2 = 1 (gdb) c Continuing. *........* Breakpoint 1, main () at /home/jurrutia/C++Src/Stars.cpp:2121 printstars(count2); (gdb)


Debugger Example(gdb) end This command cannot be used at the top level.(gdb) clear Deleted breakpoint 1 (gdb) c Continuing. **......** ***....*** ****..**** ********** ****..**** ***....*** **......** *........* Program exited normally. (gdb) q …@linux1 bin]$


System Calls

fork()

exec()

wait()

exit()

kill()

Direct invocation of kernel functions

Open()

Read()

Write()

Close()


RCS - CVSRevision Control System

Source code changes are managed programmatically to avoid undoing what has already been done.

Track all changes to between revisions

4 utilities control almost everythingci – co – rlog – rcsdiff


RCS - CVSRCS traces all changes between a

previous document and the current document and records those changes as revisions.

Each revision is numberedThe original document is 1.1

Each revision is incremented by 1


RCS Check-Inci [-options] file list

Used to create or update a RCS record

-l – Lock the source to others

-u – Unlock the source to others

-r – Revision number


RCS Check - Outco [-options] file list

Used to create source files for viewing or updating

-l – Lock the source so I can change

-u – Unlock the source for viewing

-r – Revision number to check-out


RCS rlogrlog [-options] file list

Used to view the changes made to a file.

-r – Revision number to retrieve


RCS rcsdiffrcsdiff [-options] file list

Used to view the differences between two revisions of source.

-r – Revision number to compare


Concurrent Version System

CVS works the same way as RCS but provides additional structure and control.Invokes RCS functions

CVS provides self-documenting features for utilities in the system.


Why CVS ?CVS is decentralized so a user checks out

files/directories from the repository and have his own separate stable source directory tree.

CVS can "STAMP" releases of an entire project source tree.

CVS can enable concurrent editing of files. CVS can be greatly customized to enable strong

locking of files via shell scripts or PERL scripts. CVS supports weak locking with the command 'cvs watches' and also no locking permitting concurrent editing of files.


Why not CVS?Needs a little more administration than

RCS.

Very complex and sophisticated system."State of the Art" technology.Developed with 20 to 30 years of research.It’s still evolving!!

Has a large number of commands and command options, hence a steeper learning curve for beginners.


CVS Commandscheckout – Always makes copies of

source project into your specified working directory.Pulls most recently committed version.

Creates any tree structures needed.


CVS Commandsupdate – Applies any changes

made by other users to your version of code.Notifies about overlapping changes.

add – Adds new files to the project.

remove – Removes files or directories from a project.


CVS Commandscommit – Updates the repository

project with your project changes.

diff – Displays differences between Repository and working files

Revisions of a file in the repository

1 © 2000-2002 John Urrutia. All rights reserved. Programming.

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Transcript of 1 © 2000-2002 John Urrutia. All rights reserved. Programming.