How do I do calculations with data from user input?

Question

I'm pretty new to mathematica and I'd like to create a little program that takes user input as variables which it then uses to do some calculations. I have the following code:

Clear[numcols, nullbitmap]

    DynamicModule[{numcols, nullbitmap},
 Column[{
   InputField[Dynamic[numcols], Number, 
    FieldSize -> {15, {1, Infinity}}], 
   Button[Style["Process"], 
    nullbitmap[numcols_] = 2 + ((7 + numcols)/8)]
   }]]

Print[nullbitmap]

But this doesn't print the result I and it seems that it doesn't take the 'numcols' as a variable in the calculation.

Answer 1

Try this:

Clear[numcols, nullbitmap]

DynamicModule[{numcols, nullbitmap}, 
 Column[{InputField[Dynamic[numcols], Number, 
    FieldSize -> {15, {1, Infinity}}], 
   Button[Style["Process"], nullbitmap = 2 + ((7 + numcols)/8); 
    Print[nullbitmap]]
   }]
 ]

Have fun!