error 144 in scilab

hi all, i am new to scilab.

i am getting an error wen i try to execute the following lines of code:

for example,

radius=input("Radius=?","string");
area=3.14159*radius*radius;
disp("area");

output is as follows:

-->exec('C:\Users\dell\Documents\1.6', -1)
Radius=?3
area=3.14159*radius*radius;
!--error 144
Undefined operation for the given operands.
check or define function %s_m_c for overloading.
at line 2 of exec file called by :
exec('C:\Users\dell\Documents\1.6', -1)

plz help me out wid dis basic concept. it is showing a 144 error.

reply asap...