You must declare i in the first of program not in the body of for loop it will be like this.hope it help
int main(void) {
int i; //here is the change declare it must be here
int value[] = {1, 2, 88, 42, 99};
for ( i=0; i<3; i++) {
printf ("\n%d\n", value[i]);
}
return 0;
}