本文中调用的四个函数如下：

atoi函数：将字符串转化为int类型变量

atol函数：将字符串转化为long类型变量

atoll函数：将字符串转化为long long类型变量

atof函数：将字符串转化为double类型变量

这些函数的转化过程，都是将一个字符串的可读部分取到变量中

遇到不可读的部分，则直接终止读取

调用示例：

#include <stdio.h>

#include <stdlib.h>

#define Seperate(); printf("\n=============\n\n");

int main()

{

    Seperate();

    //atoi

    printf("atoi: string to integer\n");

    const char* s00 = "1234567890";

    printf("%s -> %d\n", s00, atoi(&s00[0]));

    const char* s01 = "123.4";

    printf("%s -> %d\n", s01, atoi(&s01[0]));

    const char* s02 = "xyz";

    printf("%s -> %d\n", s02, atoi(&s02[0]));

    const char* s03 = "1234xyz";

    printf("%s -> %d\n", s03, atoi(&s03[0]));

    Seperate();

    //atol

    printf("atol: string to long\n");

    const char* s10 = "1234567890123";

    printf("%s -> %ld\n", s10, atol(&s10[0]));

    const char* s11 = "123.4";

    printf("%s -> %ld\n", s11, atol(&s11[0]));

    const char* s12 = "xyz";

    printf("%s -> %ld\n", s12, atol(&s12[0]));

    const char* s13 = "1234xyz";

    printf("%s -> %ld\n", s13, atol(&s13[0]));

    Seperate();    

    //atoll

    printf("atoll: string to long long\n");

    const char* s20 = "1234567890123";

    printf("%s -> %lld\n", s20, atoll(&s20[0]));

    const char* s21 = "123.4";

    printf("%s -> %lld\n", s21, atoll(&s21[0]));

    const char* s22 = "xyz";

    printf("%s -> %lld\n", s22, atoll(&s22[0]));

    const char* s23 = "1234xyz";

    printf("%s -> %lld\n", s23, atoll(&s23[0]));    

    Seperate();

    //atof

    printf("atof: string to double\n");

    const char* s30 = "1234567890";

    printf("%s -> %lf\n", s30, atof(&s30[0]));

    const char* s31 = "123.4";

    printf("%s -> %lf\n", s31, atof(&s31[0]));

    const char* s32 = "xyz";

    printf("%s -> %lf\n", s32, atof(&s32[0]));

    const char* s33 = "1234xyz";

    printf("%s -> %lf\n", s33, atof(&s33[0]));    

    Seperate();

    return 0;

}

运行效果：

END