C++ 从整型转换为浮点型可能会改变其值.

我研究了这个错误，但一直没能找到.另外，我对此还是个新手.我想学习C语言的基础知识，下面是我的第一个程序.我想修改函数calc中的sum，这样它就是float，以防有人除以例如2/5.

#include <stdio.h>

int getNumber1() {
    int myNumber1;
    printf("\n gib eine Zahl ein: ");
    scanf("%d", &myNumber1);
    return myNumber1;
}

int getNumber2() {
    int myNumber2;
    printf("\n gib eine weitere Zahl ein: ");
    scanf("%d", &myNumber2);
    return myNumber2;
}

char getOp() {
    char myOp;
    printf("\n gib einen Operanten ein: ");
    scanf(" %c", &myOp);
    return myOp;
}

void calc(int number1, int number2, char op) {
    if (op == '+') {
        int sum = number1 + number2;
        printf("\n\n%d %c %d = %d", number1, op, number2, sum);
    }
    if (op == '-') {
        int sum = number1 - number2;
        printf("\n\n%d %c %d = %d", number1, op, number2, sum);
    }
    if (op == '*') {
        int sum = number1 * number2;
        printf("\n\n%d %c %d = %d", number1, op, number2, sum);
    }
    if (op == '/') {
        float sum = number1 / number2;
        printf("\n\n%d %c %d = %.2f", number1, op, number2, sum);
    }
}

int main() {
    int cont = 1;
    while (cont == 1) {
        int number1 = getNumber1();
        int number2 = getNumber2();
        char op = getOp();
        calc(number1, number2, op);
        printf("\nMoechten Sie weitere Berechnungen durchfuehren? (1 fuer Ja, 0 fuer Nein): ");
        scanf("%d", &cont);
    }
    printf("\nDanke und auf Wiedersehen.");
    return 0;
}

但我得到的错误是conversion to float from int may alter its value.为什么会这样？我怎样才能解决这个错误？