Sinclair QL Beginner's Manual page 6

UPPER AND LOWER CASE
CLS 
Cls 
clS 
These are all correct and have the same effect. Some keywords are displayed partly, in upper case to
show allowed abbreviations. Where a keyword cannot be abbreviated it is displayed completely in
upper case.
USE OF QUOTES
The usual use of quotes is to define a word or sentence – a string of characters. Try:
PRINT "This works" 
The computer will respond with:
This works
The quotes are not printed but they indicate that some text is to be printed and they define exactly
what it is - everything between the opening and closing quote marks. If you wish to use the quote
symbol itself in a string of characters then the apostrophe symbol can be used instead. For example:
PRINT 'The quote symbol is "'
will work and will print
The quote symbol is "
COMMON TYPING ERRORS
The zero key is with the other numeric digits at the top of the keyboard, and is slightly
thinner.
The letter 'O' key is amongst the other letters. Be careful to use the right symbol.
Similarly avoid confusion between one, amongst the digits, and the letter 'I' amongst the
letters between one, amongst the digits, and the letter 'I' amongst the letters.
KEEP SHIFT DOWN
When using a SHIFT key hold it down while you type the other key so that the SHIFT key makes
contact before the other key and also remains in contact until after the other key has lifted.
The same rule applies to the control CTRL and alternate ALT keys which are used in conjunction with
others but you do not need those at present.
Type the two simple instructions:
CLS 
PRINT 'Hello' 
Strictly speaking these constitute a computer program, however it is the stored program that is
important in computing. The above instructions are executed instantly as you type  (ENTER)
Now type the program with line numbers:
10 CLS 
20 PRINT 'HELLO' 