函数名: ultoa

　　功 能: 转换一个无符号长整型数为字符串

　　用 法: char *ultoa(unsigned long value, char *string, int radix);

　　程序例:

　　#include
#include
int main( void )
{
unsigned long lnumber = 3123456789L;
char string[25];
ultoa(lnumber,string,10);
printf("string = %s unsigned long = %lu\n",string,lnumber);
return 0;
}

　　函数名: ungetc

　　功 能: 把一个字符退回到输入流中

　　用 法: int ungetc(char c, FILE *stream);

　　程序例:

　　#include
#include
int main( void )
{
int i=0;
char ch;
puts("Input an integer followed by a char:");
/* read chars until non digit or EOF */
while((ch = getchar()) != EOF && isdigit(ch))
i = 10 * i + ch - 48; /* convert ASCII into int value */
/* if non digit char was read, push it back into input buffer */
if (ch != EOF)
ungetc(ch, stdin);
printf("i = %d, next char in buffer = %c\n", i, getchar());
return 0;
}

　　函数名: ungetch

　　功 能: 把一个字符退回到键盘缓冲区中

　　用 法: int ungetch(int c);

　　程序例:

　　#include
#include
#include
int main( void )
{
int i=0;
char ch;
puts("Input an integer followed by a char:");
/* read chars until non digit or EOF */
while((ch = getche()) != EOF && isdigit(ch))
i = 10 * i + ch - 48; /* convert ASCII into int value */
/* if non digit char was read, push it back into input buffer */
if (ch != EOF)
ungetch(ch);
printf("\n\ni = %d, next char in buffer = %c\n", i, getch());
return 0;
}