Chapter TenChapter Ten

Developing UNIX Developing UNIX ApplicationsApplicationsIn C and C++In C and C++

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Lesson ALesson A

C Programming in aC Programming in aUNIX EnvironmentUNIX Environment

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ObjectivesObjectivesCreate simple C programsCreate simple C programs

Understand C program structureUnderstand C program structure

Use the make utility to help with program Use the make utility to help with program development and maintenancedevelopment and maintenance

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Introducing C ProgrammingIntroducing C ProgrammingC is the language in which UNIX was C is the language in which UNIX was developed and refineddeveloped and refined

Known for its efficiency and brevityKnown for its efficiency and brevity

C program is set of functionsC program is set of functions– Must have Must have mainmain function function

C programs are stored inC programs are stored in– Header files: Header files: .h.h– Body files:Body files: .c.c

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Creating a C ProgramCreating a C Program#include <stdio.h>

main() { printf("hello world\n");}

Stored as:Stored as: one.cone.cCompiled and linked as:Compiled and linked as: gcc one.cgcc one.crun as:run as: ./a.out./a.out

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Compilation ProcessCompilation Process.c and .h

.o

a.out

.i

.s

gcc -E

gcc -S

gcc -c

.a ar

gcc -o

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A simple C programA simple C program#include <stdio.h>#include <stdio.h>main(int argc, char* argv[]) {main(int argc, char* argv[]) { if (argc > 1)if (argc > 1) printf("hello %s\n", argv[1]);printf("hello %s\n", argv[1]); elseelse printf("hello world\n");printf("hello world\n");}}

command line argumentscommand line arguments

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A simple C programA simple C program

to compile:to compile:gcc two.cgcc two.c

produces:produces: a.out a.outororgcc -c two.cgcc -c two.c

produces:produces: two.o two.o

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A simple C functionA simple C function#include <math.h>#include <math.h>

int compute(int x, int y) {int compute(int x, int y) { double tx = x, ty = y, tr;double tx = x, ty = y, tr; tr = pow(tx, ty);tr = pow(tx, ty); return (int) tr;return (int) tr;}}

uses math libraryuses math library

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Multiple source filesMultiple source files

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A main programA main program#include <stdio.h>#include <stdio.h>main() {main() { int x, y, p;int x, y, p; printf("This program computes x^y\n");printf("This program computes x^y\n"); printf("Enter x: ");printf("Enter x: "); scanf("%d", &x);scanf("%d", &x); printf("Enter y: ");printf("Enter y: "); scanf("%d", &y);scanf("%d", &y); p = compute(x, y);p = compute(x, y); printf("Result: %d\n", p);printf("Result: %d\n", p);}}

asks for user inputasks for user input

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Steps to create an executableSteps to create an executable

to compile:to compile:gcc –c compute.cgcc –c compute.cgcc –c power.cgcc –c power.cgcc compute.o power.o –lm –o powergcc compute.o power.o –lm –o powerto runto run./power./power

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make utilitymake utility

has configuration file that specifies has configuration file that specifies dependencies: dependencies: makefilemakefilechecks timestamps on fileschecks timestamps on filesrecompiles necessary filesrecompiles necessary files

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makefilemakefilepower: power.o compute.opower: power.o compute.o gcc power.o compute.o -o power -lmgcc power.o compute.o -o power -lmpower.o: power.cpower.o: power.c gcc -c power.cgcc -c power.ccompute.o: compute.ccompute.o: compute.c gcc -c compute.cgcc -c compute.c

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Lesson BLesson B

C++ Programming in aC++ Programming in aUNIX EnvironmentUNIX Environment

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ObjectivesObjectives

Create a simple C++Create a simple C++

understand multi-file organization of a understand multi-file organization of a C++ programC++ program

makemake

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Introducing C++ Introducing C++ ProgrammingProgramming

C++ is a programming language that C++ is a programming language that builds on C to add object-oriented builds on C to add object-oriented capabilitiescapabilities

C and C++ are similar in many waysC and C++ are similar in many ways

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Creating a C++ ProgramCreating a C++ Program#include <iostream>

main() { cout << "hello world" << endl;}

Stored as:Stored as: one.ccone.ccCompiled and linked as:Compiled and linked as: g++ one.ccg++ one.ccrun as:run as: ./a.out./a.out

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A simple C++ programA simple C++ program#include <iostream>#include <iostream>

main(int argc, char* argv[]) {main(int argc, char* argv[]) { if (argc > 1)if (argc > 1) cout << "hello " << argv[1] << endl;cout << "hello " << argv[1] << endl; elseelse cout << "hello world\n";cout << "hello world\n";}}

command line argumentscommand line arguments

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A simple C++ programA simple C++ program

to compile:to compile:g++ two.ccg++ two.cc

produces:produces: a.out a.outororg++ -c two.ccg++ -c two.cc

produces:produces: two.o two.o

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C++ classesC++ classes

Class header and bodyClass header and bodyHeader in header fileHeader in header file .h.hBody in body fileBody in body file .cc or .C.cc or .C– includes header fileincludes header file

main function still requiredmain function still required

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A simple C++ class headerA simple C++ class header#ifndef COUNTER_H#ifndef COUNTER_H#define COUNTER_H#define COUNTER_Hclass Counter {class Counter { int value;int value; public:public: Counter();Counter(); void increment(int);void increment(int); void reset();void reset(); int getValue();int getValue();};};#endif#endif

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A simple C++ class bodyA simple C++ class body#include "Counter.h"#include "Counter.h"

Counter::Counter() {Counter::Counter() { reset();reset();}}void Counter::increment(int n=1) {void Counter::increment(int n=1) { value += n;value += n;}}void Counter::reset() {void Counter::reset() { value = 0;value = 0;}}int Counter::getValue() {int Counter::getValue() { return value;return value;}}

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main C++ programmain C++ program#include <iostream>#include <iostream>#include "Counter.h"#include "Counter.h"main() {main() { Counter c;Counter c; int value;int value; cout << "enter value: ";cout << "enter value: "; cin >> value;cin >> value; c.increment(value);c.increment(value); cout << "counter now: " cout << "counter now: " << c.getValue() << endl;<< c.getValue() << endl;}}

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makefilemakefilecount: Counter.o main.ocount: Counter.o main.o g++ Counter.o main.o -o countg++ Counter.o main.o -o countCounter.o: Counter.CCounter.o: Counter.C g++ -c Counter.Cg++ -c Counter.Cmain.o: main.Cmain.o: main.C g++ -c main.Cg++ -c main.C

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Chapter SummaryChapter Summary

The major difference between C and C++ The major difference between C and C++ is that C follows procedural principles is that C follows procedural principles and C++ primarily follows object-oriented and C++ primarily follows object-oriented programmingprogramming

The make utility is used to maintain the The make utility is used to maintain the application’s source filesapplication’s source files