C中的一些函数

#include <stdio.h>
#include <string.h>

int main()
{
    char c, s[20], *p;
    int a = 1234, b=12, *i;
    float f=3.141592653589f;
    double x = 0.12345678987654321;
    p = "How do you do"; 
    strcpy(s, "Hello, Comrade");
    i = &b;
    c = ‘\x41‘;

    printf("a=%d\n", a);         /*结果输出十进制整数a=1234*/
    printf("a=%6d\n", a);        /*结果输出6位十进制数a=  1234*/
    printf("a=%06d\n", a);       /*结果输出6位十进制数a=001234*/
    printf("a=%2d\n", a);        /*a超过2位, 按实际值输出a=1234*/
    printf("*i=%4d\n", *i);      /*输出4位十进制整数*i=  12*/
    printf("*i=%-4d\n", *i);     /*输出左对齐4位十进制整数*i=12*/
    printf("i=%p\n", i);         /*输出地址i=06E4*/
    printf("f=%f\n", f);         /*输出浮点数f=3.141593*/
    printf("f=6.4f\n", f);       /*输出6位其中小数点后4位的浮点数f=3.1416*/
    printf("x=%lf\n", x);        /*输出长浮点数x=0.123457*/
    printf("x=%18.16lf\n", x);   /*输出18位其中小数点后16位的长浮点数x=0.1234567898765432*/
    printf("c=%c\n", c);         /*输出字符c=A*/
    printf("c=%x\n", c);         /*输出字符的ASCII码值c=41*/
    printf("s[]=%s\n", s);       /*输出数组字符串s[]=Hello, Comrade*/
    printf("s[]=%6.9s\n", s);    /*输出最多9个字符的字符串s[]=Hello, Co*/
    printf("s=%p\n", s);         /*输出数组字符串首字符地址s=FFBE*/
    printf("*p=%s\n", p);        /* 输出指针字符串p=How do you do*/
    printf("p=%p\n", p);         /*输出指针的值p=0194*/

    getchar();
    return 0; 
}

/*
int sprintf ( char * str, const char * format, ... );

Write formatted data to string
[将格式化数据写入到string中]
Composes a string with the same text that would be printed if format was used on printf, but instead of being printed, the content is stored as a C string in the buffer pointed by str.
[不同于printf()的将格式化数据输出到标准输出设备上，sprintf()是将格式化数据保存在一个C字符串缓冲中]
The size of the buffer should be large enough to contain the entire resulting string (see snprintf for a safer version).
[字符串缓冲的大小应该大到足以包含所有的结果字符串]
A terminating null character is automatically appended after the content.
[sprintf()函数会自动添加一个null作为字符串结束符]
After the format parameter, the function expects at least as many additional arguments as needed for format.
[sprintf()中参量表的个数需要与格式化规定符的个数一一对应，且数量相等]

Return Value
On success, the total number of characters written is returned. This count does not include the additional null-character automatically appended at the end of the string.
[如果成功，则返回被写入的字符总数(不包含自动添加null结束符)]
On failure, a negative number is returned.
[如果失败，则返回一个负数]
*/

#include <stdio.h>

int main()
{
    char buffer[50];
    int n, a=5, b=3;
    n = sprintf(buffer, "%d plus %d is %d", a, b, a+b);
    printf("[%s] is a string %d chars long.\n", buffer, n);

    getchar();
    return 0;
}