When you open QBasic, you see a blue screen where you can type your program.
Let’s begin with the basic commands that are important in any program.
Command PRINT displays text or numbers on the screen.
The program line looks like this:
PRINT "My name is Nick."
Type the highlighted text into QBasic and press F5 to run the program. On the screen you’ll see:My name is Nick.
You must put the text in quotes, like this – "text". The text in quotes is called a string. If you put the PRINT alone, without any text, it will just put an empty line. PRINT can also put numbers on the screen. PRINT 57 will show the number 57. This command is useful for displaying the result of mathematical calculations. But for calculations, as well as for other things in the program, you need to use variables.
When you think, you keep words or numbers in your mind. This allows you to speak and to
make calculations. QBasic also needs to keep words or numbers in its memory. To do this,
you use variables, pieces of QBasic memory, which can keep information. A variable can be
named with any letter, for example – a. It can also have a longer name, which can be almost
any word. It is important to know that there are two main types of variables – that keep a
number and that keep a word or a string of words.
Numeric variables. It’s basically variables named with just a letter or a word. You tell this variable to keep a number like this:
a = 15
In other words, you assigned the value 15 to the variable a.
QBasic will now know that the variable named a keeps the number 15. Now, if you type:
and run the program, the computer will show this number on the screen.
String variables can keep so called "strings", which is basically any text or symbols (like % or £), which you put in the quotes "". You can also put numbers in a string variable, but again, you must include them in quotes, and QBasic will think that those numbers are just a part of text. The string variables look like this – a$. The $ sign tells QBasic that this variable contains text.
a$ = "It is nice to see you"
On the screen you’ll see:It is nice to see you
The PRINT command can print more that one string on the line. To do this, put the ; sign between the variables. For example, you have two variables – name$, which contains name Rob, and age, which contains the number 34. Then, to print both name and age, you type:
PRINT "Name - "; name$; ". Age - "; age
As you can see, the name of a variable can be more than just one letter – it can be a short word which describes what sort of information does this variable keep.