Choosing the 128 BASIC option from the main menu lets you write your own BASIC program. it also lets you edit a program which you have previously written, or issue a direct command for things like loading software which cannot be loaded using the easy Tape Loader.
If you are used to writing in Spectrum BASIC (see the ZX Spectrum + User Guide), you will find that 128 BASIC is very similar but contains some extra commands. The most important difference is the way in which you type in 128 BASIC.
Ordinary Spectrum BASIC commands are entered in by pressing one key (sometimes after pressing one or two others). The whole keyword (printed in small letters on the key) then appears on the screen.
In 128 BASIC none of these special key entries apply. Instead, you type each word in full, letter by letter.
You can use 128 BASIC to type in any program which was originally written for the Spectrum 128. it can also be used for many programs which were written for the 16K or 48K Spectrum, including those in the ZX Spectrum + User Guide. It does not matter that these originally used special keys to enter them. However, you may find that some programs for the earlier Spectrums contain instructions which will cause them to fail if run in 128 BASIC.
Note that the TRUE VIDEO and INVERSE VIDEO keys are not used in 128 BASIC. INVERSE effects are available by using the keywords INVERSE 1 and INVERSE 0 as described on page 31 of the ZX Spectrum + User Guide.
In 128 BASIC, EXTEND MODE is only used for a few symbols shown above the letters on the keys, such as 1. To get these symbols, press the EXTEND MODE key and then SYMBOL SHIFT and the symbol key together. The Spectrum 128 then reverts to normal typing. >=, <= and <> must be entered as two characters. GRAPHICS mode works as it does in Spectrum BASIC but you must leave GRAPHICS mode if you wish to use the cursor keys to edit a program. Colour control codes (see page 33 of the ZX Spectrum + User Guide) are not available in 128 BASIC and you should use the colour keywords instead. Spectrum BASIC programs which contain the keywords POKE or PEEK may not work correctly in 128 BASIC.
When you are typing in 128 BASIC, you can use either capitals or lower case letters except when entering music (see page 10) The other examples printed here are in capitals for clarity, but this is not essential. You also do not always need to include spaces on either side of BASIC keywords as shown in the program examples (the Spectrum + puts these in automatically). However, if you are typing a keyword next to another letter (eg, FOR N or IF A) you must put in the space. When a program line is accepted by the Spectrum 128 (see below) it automatically converts all the keywords to capitals and inserts spaces as shown in the examples.
As soon as you have selected 128 BASIC from the main menu, you will see a blank screen ready to type onto. Try typing this
10 BORDER 1:PAPER 6:INK 2:CLS
Note that you could just as well type
10 border 1:paper 6:ink 2:cls
as they mean the same to the Spectrum 128. Press [ENTER] when you reach the end of the line.
Now you want to run your program to see its effect, Type
and press [ENTER]. The screen should turn yellow with a dark blue border.
The Spectrum 128 will check each program line after you have typed it in. If you make a typing mistake which it cannot understand, it will not accept the line when you press [ENTER]. The commonest errors are spelling mistakes and missing spaces. For example, in the program line you have just entered, you might have typed
10 BORDER 1:PAPER 6:UNK 2:CLS
which has a spelling mistake.
When an error is detected, a red cursor will flash in the line. This cursor will almost always indicate the keyword which contains the first error (as it will here), but with some types of mistake this is not the case.