Floating point addition, without floats!
Python, 224 chars

This code converts a floating point input f to the integer f*2^150, does the addition using python native big integers, then converts back.

V=lambda x:((-1)**int(x[0])&lt;&lt;int(x[1:9],2))*int('1'+x[9:],2)
B=lambda x,n:B(x/2,n-1)+'01'[x&amp;1]if n else''
def A(x,y):
 v=V(x)+V(y)
 s=e=0
 if v&lt;0:s=1;v=-v
 while v&gt;=1&lt;&lt;24:v/=2;e+=1
 if e&gt;254:v=0
 return'%d'%s+B(e,8)+B(v,23)