#include?
#include?
#include??
?
#define?N?4?

double?Tx=0;
int?code_length;?
double?freq[]={00.80.821};//符號累積密度函數
int?i;
?

void?encode（void）
{???
	char?str[50];
????int?jstrlength;
	double?lower=0upper=1ul;	?
	printf（“please?enter?a?string?using?letter?1-3:“）;
	scanf（“%s“&str）;
	strlength=strlen（str）;
	if（strlength!=0）
	{???
	?	for（j=0;j		{
			l=lower+（upper-lower）*freq[str[j]-‘1‘];
			u?=lower+（upper-lower）*freq[str[j]-‘1‘+1];
			lower=l;upper=u;
		?	printf（“lower=%fupper=%f\n“lowerupper）;
			
		}
?????	Tx=（upper+low