What range of values does 480*RND give you?
The number will be zero up to slightly less than 480.
An arithmetic expression like 480*RND
might give you a number like
235.34901.
This is a floating point number.
The pixels of the graphics screen are
"little graph paper squares" with integer column and row numbers.
QBasic will let you use floating point numbers
in the PSET
statement,
but it is better to convert the floating point number to an integer.
The function INT
does just that.
INT( 235.34901 )
gives you 235.
INT( 13.89490 )
gives you 13.
Notice that this is different from rounding.
For positive numbers, the fractional part of the number is just dropped.
(This is sometimes called truncation.)
What is INT( 25.50 )?