rand


rand

Obtains a random integer value

 #include <stdlib.h> int rand( void ); 

The rand( ) function returns a pseudorandom number between 0 and RAND_MAX. The symbolic constant RAND_MAX is defined in stdlib.h, and is equal to at least 32,767 (or 215 -1).

To initialize the pseud-random number generator, call the srand( ) function with a new seed value before the first call to rand( ). This step ensures that rand( ) provides a different sequence of random numbers each time the program runs. If you call rand( ) without having called srand( ), the result is the same as if you had called srand( ) with the argument value 1.

Example

 printf( "Think of a number between one and twenty.\n"         "Press Enter when you're ready." ); getchar( ); srand( (unsigned)time( NULL ) ); for ( int i = 0; i < 3; i++ )       // We get three guesses. {   printf( "Is it %u? (y or n) ", 1 + rand( ) % 20 );   if ( tolower( getchar( ) ) == 'y' )   {     printf( "Ha! I knew it!\n" );     exit( 0 );   }   getchar( );                        // Dicard newline character. } printf( "I give up.\n" ); 



C(c) In a Nutshell
C in a Nutshell (In a Nutshell (OReilly))
ISBN: 0596006977
EAN: 2147483647
Year: 2006
Pages: 473

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