The computer creates a box in memory and calls it “A”. It puts the number 8 in this box.

Now type:

20 LET B=10

press ENTER

 

 

The computer creates a box called “B” and places 10 into it.

Type:

30 LET B=15

press ENTER

 

 

Since there is a box called “B” already with a value of 10 in it, it doesn’t make another box called “B” with a value of 15 in it. The number 10 is just replaced with the number 15.

Now type:

40 LET C=A+B

press ENTER

 

 

This statement is a bit more complicated. Here’s how it works. First, the computer searches for a memory box called “B” and finds the number 15. The “+” sign tells the computer to add the numbers found in “A” and “B” together. It computes this and the answer is

23.Now, where is the answer placed? The “=” tells the computer to store the answer in a memory box called “C”. The computer searches for a box called “C”. It doesn’t find one so it creates one in memory and then puts the answer there.

Of course, if there was a memory variable called “C” that had a number in it from a previous operation, the old number would be replaced by the new one in this statement.

Now let’s finish this by typing:

50

PRINT “FIRST NUMBER”; A

press ENTER

60

PRINT “SECOND NUMBER”; B

press ENTER

70

PRINT “THE SUM IS”; C

press ENTER

RUN

 

 

 

 

 

37