Hex To Character Conversion Problem

I am Trying to Split a hexa value and read it over the serial port let me show you what i mean by that :

<per>
char arr[10]=(0);
int i,k,l;

arr[0]=0x11;
arr[1]=0x12;
: :
arr[7]=0x59;
arr[8]=0x5F;
arr[9]=0x90;

for(i=0;i<10;i++)
{ k=(arr[i]/0x10)>0x09?(arr[i]/0x10)+55:(arr[i]/0x10)+48;
l=(arr[i]%0x10)>0x09?(arr[i]%0x10)+55:(arr[i]%0x10)+48;
putchar(k);
putchar(l);
}

</per>

I am Getting Proper out put for values which are below 90 ie 1A or 2F or 44 or 39 but when value becomes 90 or 91 or A1 i am not getting proper out put. I just cant locate my mistake. Please Tell me where i am going wrong.

Thank You.
Ajay