Data Types
Qbasic has 5 'primitive' Data Types, all listed in the table below.
Each data type has a specific range of values that it is capable of handling. The main purpose of
this is so that you can choose the type of value that you need for your computations. If you only need
your variable to be between 0 and 100, you obviously wouldn't use the largest avaliable data type, because
it is a waste of memory.
Data Types:
| Type Name: |
Symbol: |
Max value |
Min Value |
| String |
$ |
32,767 characters |
0 characters |
| Integer |
% |
32,767 |
-32,768 |
| Long Integer |
& |
2,147,483,647 |
-2,147,483,648 |
| Single Precision |
! |
+/- 3.402823 x 10^38 |
+/- 1.401298 x 10^-45 |
| Double Precision |
# |
+/- 1.7976931x10^308 |
+/- 4.940656x10^-324 |
The CONST keyword is used to indicate the binding of a value to a specific variable for the
duration of the program, example:
CONST pi = 3.141592654
If you try to change the value of pi you will get an error like: "Duplicate definition"
The final data type is the user defined data type, which is essentially a data type that you create out of the above types. The construction and
use of these can be found inside of the tutorial.
Notes on Data Types:
1) One thing that you may want to note is that the double precision is just an estimate
of any value that you give it so it may not always be accurate. The same is true for the single precision, but it is not quite as bad.
I reccomend that you try these and see what comes up, just to get an Idea of what is going on with them.
2) Another issue to be addressed here is
the notation. The help file in QBasic uses a different notation than I do here. I used normal scientific notation. If you are not familiar with that,
all that it means is x10^number is just the number of decimal places, a (-) sign in front of the 'number' means that the number is a fraction, and the larger the
negative number the smaller the fraction.