decimal to octal,binary and Hexadecimal conversion

#include< stdio.h>
#include< conio.h>
void convrt(int a,int b);
void hexdec(int a);
main()
{
int a,c,r;
char cc;
do
{
clrscr();
printf("\n\n\n\t\tMenu");
printf("\n\n\tConvert decimal to");
printf("\n\n\t1.Binary\n\n\t2.Octal\n\n\t3.Hexadecimal\n\n\t4.Exit\n\n Enter your choice : ");
scanf("%d",&c);
if(c==4)
goto ent;
printf("\n\n Enter the decimal no : ");
scanf("%d",&a);
switch(c)
{
case 1:
convrt(a,2);
break;
case 2:
convrt(a,8);
break;
case 3:
hexdec(a);
break;
}
getch();
printf("\n\n Do you want to continue : ");
cc=getche();
}
while(cc=='y'||cc=='Y');
ent:
getch();
}

void convrt(int a,int b)
{
int n,i=1,p=0;
while(a!=0)
{
n=a%b;
p=p+n*i;
a=a/b;
i=i*10;
}
printf(" result= %d ",p);
}
void hexdec(int a)
{
char h[15];
int uu,r,i;
for(i=0;a!=0;i++)
{
r=a%16;
if(r<=9)
{
//printf("%d",48+r);
h[i]=char(48+r);
}
else if(r>9)
{
h[i]=char(55+r);
}
uu=i;
a=a/16;
}
for(i=uu;i>=0;i--)
printf("%c",h[i]);
}