C/Data Type/Static
Содержание
Define and use static variable
<source lang="cpp">
- include <stdio.h>
void f(void); int main(void) {
int i;
for(i = 0; i < 10; i++)
f();
return 0;
} void f(void) {
static int count = 0;
count++;
printf("count is %d\n", count);
}
</source>
Define static variable inside function
<source lang="cpp">
- include <stdio.h>
int g = 10; void f(); main() {
int i =0;
f();
printf(" after first call \n");
f();
printf("after second call \n");
f();
printf("after third call \n");
} void f() {
static int k=0;
int j = 10;
printf("k= %d j= %d",k,j);
k = k + 10;
}
</source>
Demonstrate the use for permanent and temporary storage
<source lang="cpp">
- include <stdio.h>
int main() {
int i;
for (i = 0; i < 3; ++i) {
int temporary = 1;
static int permanent = 1;
printf("Temporary %d Permanent %d\n",temporary, permanent);
++temporary;
++permanent;
}
return (0);
}
</source>
Find out the address of a static variable in a function
<source lang="cpp">
- include <stdio.h>
int myFunction(int n); long old=0; long current=0; int main() {
int k = 4,i;
long diff;
i =myFunction(k);
printf("i = %d\n",i);
diff = old - current;
printf("stack overheads are %16lu\n",diff);
} int myFunction(int n) {
int j;
static int staticVariable=0;
if(staticVariable==0){
old =(long) &j;
}
if(staticVariable==1){
current =(long) &j;
}
staticVariable++;
printf("the address of j and staticVariable is %16lu %16lu\n",&j,&staticVariable);
if(n<=0){
return(1);
}else{
return(n*myFunction(n-1));
}
}
</source>
Static versus automatic variables
<source lang="cpp">
- include <stdio.h>
/* Function test1 with an automatic variable */ void test1(void) {
int count = 0;
printf("\ntest1 count = %d ", ++count );
} /* Function test2 with a static variable */ void test2(void) {
static int count = 0;
printf("\ntest2 count = %d ", ++count );
} int main() {
int i = 0;
for( i = 0; i < 5; i++ )
{
test1();
test2();
}
}
</source>
