关于C的声明问题

问题描述

#include<stdio.h>
#define MONTHS 13
int main(void)
{
    char m[MONTHS] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
    int i;
    print("%s%13s", "Input", "output");
    for(i=1 ; i<MONTHS ; i++){
        printf("%7c%13c", i, m);
    }
    return 0;
}

This is my coding and may i know is it the declaration of the variable char wrong?

推荐答案

#define MONTHS 12

char* m[MONTHS] =
{
"January", "February", "March",
"April", "May", "June",
"July", "August", "September",
"October", "November", "December"
};

int i;

for(i=0 ; i<MONTHS ; i++)
{
    printf("%d: %s\n", i + 1, *(m + i));
}

请注意我是如何创建char*数组(而不是char数组)的.

Note how I''ve created an array of char* (and not an array of char).

const char * m[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};

(您实际上不需要定义MONTHS).

(you don''t really need to define MONTHS).

char *m[MONTHS] = {"", "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
    int i;
    printf("%s%13s\n", "Input", "output");
    for(i=1 ; i<xMONTHS ; i++){
        printf("%7d%13s\n", i, m[i]);
    }

1.简单来说，字符串是指向char的指针(好吧，我知道这简化了它，但是这个想法大体上是正确的)-因此，您需要正确声明"m".

2.数组是从零开始的-因此要使用索引1到12，需要将第零个元素用作虚拟对象.

3.您的格式字符串需要反映出您试图打印一个整数和一个字符串而不是2个字符的事实.

4.您不能只打印"m"-您需要指定数组的元素.

5.格式字符串中的换行符将使您的输出更具可读性-它们必须是显式的，而不是隐含的.

6.您可能会有用地获得Kernighan&的副本.里奇( http://en.wikipedia.org/wiki/The_C_Programming_Language [ [ ^ ])可以提供一些保护措施，以防止黑客喜欢的普遍存在的缓冲区溢出错误！

1. In simple terms a string is a pointer to a char (OK I know that oversimplifies it, but the idea''s roughly right) - so you need to get your declaration of ''m'' right.

2. Arrays are zero based - so to use indices 1 to 12, you need the zero''th element as a dummy.

3. Your format strings need to reflect the fact that you are trying to print an integer and a string - not 2 chars.

4. You can''t just print ''m'' - you need to specify the element of the array.

5. New line characters in the format strings will make your output more readable - they need to be explicit and are not implied.

6. You might usefully get hold of a copy of Kernighan & Ritchie (http://en.wikipedia.org/wiki/The_C_Programming_Language[^]) which (at least when I got it) was the Bible for learning C (and any C-like) language.

7. Depending on your development environment you might also consider ditching functions like printf for the string safe counterparts like StringCchPrintf (http://msdn.microsoft.com/en-us/library/ms647466(VS.85).aspx[^]) that offer some protection against ubiquitous buffer overrun bugs beloved of hackers!

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