fig05_12.c

C程序设计经典教程第5版程序示例,比较适合初级c语言的学生

/* Fig. 5.12: fig05_12.c
   A scoping example */
#include <stdio.h>

void useLocal( void );       /* function prototype */
void useStaticLocal( void ); /* function prototype */
void useGlobal( void );      /* function prototype */

int x = 1; /* global variable */

/* function main begins program execution */
int main( void )
{
   int x = 5; /* local variable to main */

   printf("local x in outer scope of main is %d\n", x );

   { /* start new scope */
      int x = 7; /* local variable to new scope */

      printf( "local x in inner scope of main is %d\n", x );
   } /* end new scope */

   printf( "local x in outer scope of main is %d\n", x );

   useLocal();     /* useLocal has automatic local x */
   useStaticLocal(); /* useStaticLocal has static local x */
   useGlobal();      /* useGlobal uses global x */
   useLocal();       /* useLocal reinitializes automatic local x */
   useStaticLocal(); /* static local x retains its prior value */
   useGlobal();      /* global x also retains its value */

   printf( "\nlocal x in main is %d\n", x );

   return 0; /* indicates successful termination */

} /* end main */

/* useLocal reinitializes local variable x during each call */
void useLocal( void )
{
   int x = 25;  /* initialized each time useLocal is called */

   printf( "\nlocal x in useLocal is %d after entering useLocal\n", x );
   x++;
   printf( "local x in useLocal is %d before exiting useLocal\n", x );
} /* end function useLocal */

/* useStaticLocal initializes static local variable x only the first time 
   the function is called; value of x is saved between calls to this
   function */
void useStaticLocal( void )
{
   /* initialized only first time useStaticLocal is called */
   static int x = 50;  

   printf( "\nlocal static x is %d on entering useStaticLocal\n", x );
   x++;
   printf( "local static x is %d on exiting useStaticLocal\n", x );
} /* end function useStaticLocal */

/* function useGlobal modifies global variable x during each call */
void useGlobal( void )
{
   printf( "\nglobal x is %d on entering useGlobal\n", x );
   x *= 10;
   printf( "global x is %d on exiting useGlobal\n", x );
} /* end function useGlobal */



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