Operation Manual

A beginner’s guide to Scratch
27
We’re not finished yet. We’ve told the program to add our numbers, but we need
to store that answer in one of our variables.
From Variables in the Blocks Palette, drag “set [first_number] to [0]” to the Scripts
tab. Change “first_number” to “result” and drag your “add” operator onto the
number “0”. Your block should look like this:
Notes:
Finally, we also need to tell Scratch to display the answer to the sum. Otherwise,
it will keep it to itself (and that’s no good to us).
Click on Looks in the Blocks Palette. Select “say [Hello!]” and drag it on to the
Scripts tab. From Variables, drag the variable “result” and drop it onto “Hello!”.
The image below will show you what we mean.
And that’s it! I have included the whole program below. We’ve added in some
extra blocks, to make the cat a bit chattier but the basics are the same as the
script we built above.
and
But hang on a minute: if you tried to make the cat do all the homework you will
have noticed a big problem.
The cat can only do addition! Don’t panic – a quick edit to change the program
slightly will do the trick.
Use this screen-
shot to build the
whole script. And
remember, each
time you want the
cat to do another
sum you will have
to click on the
green flag.
Tip...
Make sure all the
blocks snap into
place properly,
especially when
you have to snap
blocks on top of
other blocks.