我不知道哪個才是對的...

這個簡單,
把Code打上去,
Compiler之後就知道了...
另外你自己也要下功夫去學C語言,
這不是甚麼很困難的問題...

#include <stdio.h>

int main() {
    float ary[] = {1, 2, 3, 4, 5, 6, 7, 8, 9 };
    float *ptr = ary;
    float *pEnd = ary + sizeof(ary)/sizeof(float) - 1;
    
    printf("--- 基礎資料 ---\n");
    while (ptr <= pEnd) {
        printf("pointer = %p \t value = %f\n", ptr, *ptr);
        ptr++;
    }
    printf("--- 基礎資料 ---\n");
    
    float *ptr2 = ary;
    printf("--- 乘以10 ---\n");
    while (ptr2 <= pEnd) {
        *ptr2 *= 10.0;
        ptr2++;
    }
    
    float *ptr3 = ary;
    printf("--- 新資料 ---\n");
    while (ptr3 <= pEnd) {
        printf("pointer = %p \t value = %f\n", ptr3, *ptr3);
        ptr3++;
    }
    printf("--- 新資料 ---\n");
    
    return 0;
}

執行結果:

--- 基礎資料 ---
pointer = 0x7ffee939da90 	 value = 1.000000
pointer = 0x7ffee939da94 	 value = 2.000000
pointer = 0x7ffee939da98 	 value = 3.000000
pointer = 0x7ffee939da9c 	 value = 4.000000
pointer = 0x7ffee939daa0 	 value = 5.000000
pointer = 0x7ffee939daa4 	 value = 6.000000
pointer = 0x7ffee939daa8 	 value = 7.000000
pointer = 0x7ffee939daac 	 value = 8.000000
pointer = 0x7ffee939dab0 	 value = 9.000000
--- 基礎資料 ---
--- 乘以10 ---
--- 新資料 ---
pointer = 0x7ffee939da90 	 value = 10.000000
pointer = 0x7ffee939da94 	 value = 20.000000
pointer = 0x7ffee939da98 	 value = 30.000000
pointer = 0x7ffee939da9c 	 value = 40.000000
pointer = 0x7ffee939daa0 	 value = 50.000000
pointer = 0x7ffee939daa4 	 value = 60.000000
pointer = 0x7ffee939daa8 	 value = 70.000000
pointer = 0x7ffee939daac 	 value = 80.000000
pointer = 0x7ffee939dab0 	 value = 90.000000
--- 新資料 ---

我多加了把 pointer 印出來, pointer 部分,不同機器執行結果不一定相同.

指標的寫法嗎？
好久沒練習C語言了

#include <stdio.h>

void forEach(void *ary, int size, int count, void (*func)(void *data));
void mulTen(void *data);
void printData(void *data);

int main()
{
    float ary[] = {1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int size=sizeof(*ary);
    int count=sizeof(ary)/sizeof(*ary);
    printf("before:\n");
    forEach(ary, size, count, printData);
    forEach(ary, size, count, mulTen);
    printf("\nafter:\n");
    forEach(ary, size, count, printData);
    return 0;
}

void forEach(void *ary, int size, int count, void (*func)(void *data))
{
    int i;
    for(i=0; i<count; ++i) {
        func((char*)ary+i*size);
    }
}

void mulTen(void *data)
{
    *(float*)data=*(float*)data*10;
}

void printData(void *data)
{
    printf("%.2f ",*(float*)data);
}