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37. MULTITHREADING C++ Multithreading is a specialized form of multitasking and a multitasking is the feature that allows your computer to run two or more programs concurrently. In general, there are two types of multitasking: process-based and thread-based. Process-based multitasking handles the concurrent execution of programs. Thread-based multitasking deals with the concurrent execution of pieces of the same program. A multithreaded program contains two or more parts that can run concurrently. Each part of such a program is called a thread, and each thread defines a separate path of execution. C++ does not contain any built-in support for multithreaded applications. Instead, it relies entirely upon the operating system to provide this feature. This <strong>tutorial</strong> assumes that you are working on Linux OS and we are going to write multi-threaded C++ program using POSIX. POSIX Threads, or Pthreads provides API which are available on many Unix-like POSIX systems such as FreeBSD, NetBSD, GNU/Linux, Mac OS X and Solaris. Creating Threads The following routine is used to create a POSIX thread: #include pthread_create (thread, attr, start_routine, arg) Here, pthread_create creates a new thread and makes it executable. This routine can be called any number of times from anywhere within your code. Here is the description of the parameters: Parameter Description thread An opaque, unique identifier for the new thread returned by the subroutine. attr An opaque attribute object that may be used to set thread attributes. You can specify a thread attributes object, or NULL for the default values. start_routine The C++ routine that the thread will execute once it is created. 274
C++ arg A single argument that may be passed to start_routine. It must be passed by reference as a pointer cast of type void. NULL may be used if no argument is to be passed. The maximum number of threads that may be created by a process is implementation dependent. Once created, threads are peers, and may create other threads. There is no implied hierarchy or dependency between threads. Terminating Threads There is following routine which we use to terminate a POSIX thread: #include pthread_exit (status) Here pthread_exit is used to explicitly exit a thread. Typically, the pthread_exit() routine is called after a thread has completed its work and is no longer required to exist. If main() finishes before the threads it has created, and exits with pthread_exit(), the other threads will continue to execute. Otherwise, they will be automatically terminated when main() finishes. Example: This simple example code creates 5 threads with the pthread_create() routine. Each thread prints a "Hello World!" message, and then terminates with a call to pthread_exit(). #include #include #include using namespace std; #define NUM_THREADS 5 void *PrintHello(void *threadid) { long tid; tid = (long)threadid; cout
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About the Tutorial C++ is a middle-
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Enumerated Types ..................
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Function Declarations .............
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Structures as Function Arguments ..
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Data Encapsulation Example ........
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My First CGI program ..............
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C++ The ANSI standard has been stab
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C++ C++ Compiler: This is an actual
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3. BASIC SYNTAX C++ When we conside
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C++ add(x, y); A block is a set of
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C++ ??= # ??/ \ ??' ^ ??( [ ??) ] ?
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C++ cout
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C++ The following table shows the v
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C++ typedef int feet; Now, the foll
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C++ type variable_list; Here, type
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C++ Same concept applies on functio
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C++ Global Variables Global variabl
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8. CONSTANTS/LITERALS C++ Constants
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C++ \a Alert or bell \b Backspace \
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C++ } cout
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C++ j = 50000; i = j; cout
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C++ The static storage class instru
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C++ extern int count; void write_ex
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C++ ++ Increment operator, increase
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C++ operand is greater than or equa
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C++ Line 5 - b is either greater th
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C++ Bitwise operator works on bits
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C++ c = ~a; // -61 = 1100 0011 cout
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C++ Copy and paste the following C+
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C++ Condition ? X : Y Conditional o
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C++ int b = 10; int c = 15; int d =
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C++ do...while loop Like a ‘while
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C++ } return 0; When the above code
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C++ { } cout
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C++ } When the above code is compil
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C++ 2 is prime 3 is prime 5 is prim
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C++ Example #include using namespa
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C++ the ‘for’ loop are required
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C++ for equality against a list of
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C++ When the above code is compiled
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C++ An if can have zero to many e
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C++ switch(expression){ case consta
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C++ case 'D' : cout
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C++ C++ specifies that at least 256
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14. FUNCTIONS C++ A function is a g
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C++ Calling a Function While creati
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C++ in the call. This means that ch
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C++ temp = *x; /* save the value at
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C++ int main () { // local variable
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C++ Total value is :300 Total value
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C++ cout
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C++ double d = 200.374; // mathemat
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16. ARRAYS C++ C++ provides a data
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C++ for ( int j = 0; j < 10; j++ )
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C++ Multidimensioned arrays may be
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C++ Once you store the address of f
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C++ { . . . } Way-3 Formal paramete
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C++ . . } Second point to remember
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C++ 110
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C++ int main () { char greeting[6]
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C++ strcat( str1, str2): HelloWorld
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18. POINTERS C++ C++ pointers are e
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C++ // print the address stored in
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C++ convention, if a pointer contai
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C++ int main () { int var[MAX] = {1
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C++ Address of var[1] = 0xbfce42d4
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C++ Above statement is valid and wi
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C++ char *names[MAX] = { "Zara Ali"
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C++ Passing Pointers to Functions C
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C++ } return avg; When the above co
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C++ 613357504 1377296355 1530315259
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C++ // declare simple variables int
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C++ int temp; temp = x; /* save the
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C++ vals[4] = 50 When returning a r
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C++ hours:minutes:seconds year\n\0.
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C++ using namespace std; int main(
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C++ using namespace std; int main(
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C++ Error message : Unable to read.
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C++ int }book; book_id; Accessing S
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C++ using namespace std; void print
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C++ #include #include using names
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C++ Now, you can use Books directly
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C++ Both of the objects Box1 and Bo
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C++ created previously. C++ friend
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C++ { public: double length; double
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C++ internal representation of a cl
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C++ A private member variable or fu
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C++ You will learn derived classes
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C++ Line::Line(void) { cout
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C++ Line line(10.0); // get initial
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C++ } cout
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C++ } cout
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C++ } *ptr = len; Line::Line(const
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C++ friend class ClassTwo; Consider
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C++ int main( ) { } cout
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C++ Constructor called. Box2 is equ
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C++ Let us try the following exampl
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C++ }; Box(double l=2.0, double b=2
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24. INHERITANCE C++ One of the most
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C++ Total area: 35 Access Control a
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C++ }; public: int getCost(int area
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C++ 25. OVERLOADING (OPERATOR & FUN
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C++ Box operator+(const Box&, const
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C++ cout
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C++ #include using namespace std;
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C++ Time(int h, int m){ hours = h;
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C++ class Box { double length; doub
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C++ } return 0; When the above code
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C++ } { cout and the stream insert
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C++ Second Distance :F : 5 I : 11 T
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C++ } T2.displayTime(); T2++; T2.di
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C++ The function call operator () c
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C++ int arr[SIZE]; public: safearay
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C++ static int i, j; public: void f
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C++ } When the above code is compil
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Page 238 and 239: C++ As you can see, each of the chi
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Page 242 and 243: C++ Designing Strategy Abstraction
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Page 246 and 247: 29. INTERFACES C++ An interface des
Page 248 and 249: C++ }; int getArea() { return (widt
Page 250 and 251: 30. FILES AND STREAMS C++ So far, w
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Page 256 and 257: C++ Throwing Exceptions Exceptions
Page 258 and 259: C++ Because we are raising an excep
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Page 262 and 263: C++ double* pvalue = NULL; if( !(pv
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Page 270 and 271: 34. TEMPLATES C++ Templates are the
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Page 278 and 279: C++ #if 0 /* This is commented part
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Page 282 and 283: 36. SIGNAL HANDLING C++ Signals are
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Page 294 and 295: 38. WEB PROGRAMMING C++ What is CGI
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Page 298 and 299: C++ Variable Name Description CONTE
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Page 302 and 303: C++ You can pass information by sim
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Page 308 and 309: C++ if( !fi->isEmpty() && fi != (*f
Page 310 and 311: C++ Passing Dropdown Box Data to CG
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Page 318 and 319: 39. STL TUTORIAL C++ Hope you have
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