One of the reasons for buying the ZX Spectrum in the first place was the ability
to use colour on the TV screen. The screen is divided into two areas. The outer
part is referred to as BORDER,
the central area as PAPER.
It is possible to change the colours of these two sections at will, both directly
from the keyboard and in a program.
The
ZX Spectrum has eight colours to play with, and these are given numbers
between 0 and 7. Although the colours look in random order, they do
in fact give decreasing shades of grey on a monochrome TV.
Here is a list of them for reference; they are also written over the appropriate
number keys:
0 black
1 blue
2 red
3 purple, or magenta
4 green
5 pale blue, or cyan
6 yellow
7 white When
the computer is first switched on the system works in black and white.
So the normal value for BORDER and PAPER is 7 i.e., white.
The colour of any character appearing on the screen is defined by the
INK command. This is normally 0, i.e., black. initially the three
commands controlling the screen colours are set by the computer.
However, you can change these values. For example key
BORDER
2 If
you remembered to press the ENTER key, the border should now
change from white to red. This includes the area at the bottom where
commands and instructions are typed in. Try typing in other numbers
and see how the colours change.
Now try changing the centre of the screen area by keying
PAPER
5 The
PAPER command is one of the extended mode commands as mentioned
earlier. It is obtained by typing both CAPS SHIFT and SYMBOLS
SHIFT at the same time. PAPER is then a shifted C.
When the ENTER key is pressed twice the centre of the screen
should change to pale blue. The first ENTER cancels the PAPER
command already stored in the computer, but only when the second ENTER
is pressed (causing the computer to LIST any program and therefore
rebuild the screen information) does the new PAPER colour get
used. If you are using a colour television, and it hasn't changed colour,
try adjusting the colour controls on the television, and maybe the tuning
control.
The INK command
is similar to the PAPER
command and controls the colour of the characters appearing on the PAPER
section of the screen. Obviously if the INK
and PAPER colours are
the same nothing will appear on the screen!
The BORDER,
PAPER and INK
commands can be used in programs. Here is a simple one to show the range of colours
available:
10
FOR x=0 TO 7
20 BORDER x
30 PAPER 7-x: CLS
40 PAUSE 50
50
NEXT x
This
program, when RUN, goes through the eight colours, contrasting
the PAPER and BORDER colours. The CLS command after
PAPER forces the computer to rebuild the screen image and use
the new PAPER colour. The PAUSE command stops the program
for 1 second so that we can see what's happening (Try running the program
with the PAUSE left out.) To show how the INK command
works type in the foliowing program, after a NEW command.
10
BORDER 7
20 PAPER 1
30 INK 4
40 PRINT "Green characters on blue background" There
are other commands associated with the colour capabilities of the ZX
Spectrum, and these are detailed in the BASIC programming manual.
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