設計壹個程序，輸入壹個十進制整數，輸出相應的十六進制數。設計壹個函數實現數制轉換。

#include<stdio.h>

void main()

{char b[]="0123456789ABCDEF";

long int n,x;

int i,a[40];

printf("\n Please input n=");

scanf("%ld",&n);

x=n;i=0;

while(x>0)

{a[i]=x%16;

x=x/16;

i++;

}

while(i>0)

{printf("%c",b[a[i-1]]);

i--;

}

printf("\n");

}

對於大數轉換可以用如下程序：

#include "Stdio.h"

#include "Conio.h"

char result[100];

int pos;

void change(int *num);

int main(void)

{

char str[100];

int num[100];

int bin[300]={0};

int quot[100],residue=0;

int i,j,k=0,suffix=0,index=0;

puts("Input a decimal number:");

gets(str);

for(i=0;i<strlen(str);num[i]=str[i]-48,i++);

j=i-1;

while(j>=0)

{

num[j]%2?(bin[k++]=1):(bin[k++]=0);

while(index<=j)

{

residue+=num[index];

if(residue>=2)

quot[suffix++]=residue/2;

else if(index)

quot[suffix++]=0;

residue=(num[index]%2)*10;

index++;

}

for(i=0;i<suffix;num[i]=quot[i],i++);

j=suffix-1;

residue=suffix=index=0;

}

for(i=0;i<k;change(bin+i),i+=4);

for(i=pos-1;i>=0;printf("%c",result[i]),i--);

getch();

return 0;

}

void change(int *num)

{

if(num[3]==0&&num[2]==0&&num[1]==0&&num[0]==0)

sprintf(result+pos,"%c",'0');

if(num[3]==0&&num[2]==0&&num[1]==0&&num[0]==1)

sprintf(result+pos,"%c",'1');

if(num[3]==0&&num[2]==0&&num[1]==1&&num[0]==0)

sprintf(result+pos,"%c",'2');

if(num[3]==0&&num[2]==0&&num[1]==1&&num[0]==1)

sprintf(result+pos,"%c",'3');

if(num[3]==0&&num[2]==1&&num[1]==0&&num[0]==0)

sprintf(result+pos,"%c",'4');

if(num[3]==0&&num[2]==1&&num[1]==0&&num[0]==1)

sprintf(result+pos,"%c",'5');

if(num[3]==0&&num[2]==1&&num[1]==1&&num[0]==0)

sprintf(result+pos,"%c",'6');

if(num[3]==0&&num[2]==1&&num[1]==1&&num[0]==1)

sprintf(result+pos,"%c",'7');

if(num[3]==1&&num[2]==0&&num[1]==0&&num[0]==0)

sprintf(result+pos,"%c",'8');

if(num[3]==1&&num[2]==0&&num[1]==0&&num[0]==1)

sprintf(result+pos,"%c",'9');

if(num[3]==1&&num[2]==0&&num[1]==1&&num[0]==0)

sprintf(result+pos,"%c",'A');

if(num[3]==1&&num[2]==0&&num[1]==1&&num[0]==1)

sprintf(result+pos,"%c",'B');

if(num[3]==1&&num[2]==1&&num[1]==0&&num[0]==0)

sprintf(result+pos,"%c",'C');

if(num[3]==1&&num[2]==1&&num[1]==0&&num[0]==1)

sprintf(result+pos,"%c",'D');

if(num[3]==1&&num[2]==1&&num[1]==1&&num[0]==0)

sprintf(result+pos,"%c",'E');

if(num[3]==1&&num[2]==1&&num[1]==1&&num[0]==1)

sprintf(result+pos,"%c",'F');

pos++;

}