GAGS v2.3
by Gerrit Hillebrand
STATEMENTS
GAGS
This statement shows the version number.
CLS
Selects text mode and clears the screen.
ATKEY (A,B,C,....) (a,b,c,....)
Using this statement, you can assign keys to linenumbers or labels. E.g.
ATKEY (A,F,J) (100,k,90)
If the [A]-key is pressed, a jump will be made to line 100. If the [F]-key
is pressed, a jump will be made to label k.
JOYSTK A,B,C
If a joystick is available, it will be scanned, and the appropriate
variables will be update according to the joysticks position.
A - variable A to Z: +1 if joystick right,
-1 if joystick left.
B - variable A to Z: +1 if joystick up,
-1 if joystick down.
C - variable A to Z: =0 if fire button not pressed,
<>0 if fire button pressed.
INV
Inverts the screen, in each graphics mode.
BORDER x,y
Draws a rectangle at a certain offset from the border.
x - offset from left and right hand side of screen,
y - offset from top and bottom of screen.
PAINT x,y
PAINT x,y,p
Fills a closed area, using one of 32 user definable patterns.
x - x coordinate of start position,
y - y coordinate of start position,
p - pattern number (see CREATE), solid fill if p omitted.
CUBE p,m,x,y,b,h
Draws a rectangle or parts of it.
p - plotting mode: 0=reset, 1=set, 2=invert.
m - feature mode: 0=draw complete rectangle,
1=draw rectangle until first set pixel,
2=draw rectangle from first set pixel onwards,
3=draw rectangle until first set pixel, and from the
next set pixel onwards,
4=start drawing at first set pixel, until next set
pixel.
x - x coordinate lower left corner,
y - y coordinate lower left corner,
b - width,
h - height.
CIRCLE p,x,y,r
Draws a circle in each graphics mode.
p - plotting mode: 0=reset, 1=set, 2=invert.
x = x coordinate center,
y = y coordinate center,
r = radius.
PIXEL x,y,z
Checks whether a pixel is set or reset.
x - x coordinate,
y = y coordinate,
Z = variable A to Z, result.
WINDOW m,x,y,b,h
Defines a windows in which drawing is allowed or not.
m = mode: =0 draw only outside window,
=1 draw only inside window.
x = x coordinate lower left corner,
y = y coordinate lower left corner,
b = width,
h = height.
WOFF
Disables window.
FILL a,b,x
Fills memory from a to b with value x.
SCROLL e
Scrolls the screen in every direction, depending on extension e:
U - up, 8 pixels,
D - down, 8 pixels,
L - left, 8 pixels,
R - right, 8 pixels.
HLINE p,x1,y1,x2,y2,l,f,A,B
Draws a line from a start position to a position with a certain
x coordinate, which lies on the line between start and end position.
p - plotting mode: 0=reset, 1=set, 2=invert,
x1,y1 - coordinates start position,
x2,y2 - coordinates end position,
l - x coordinate end pixel,
f - pixel feature: =0 draw until end pixel,
=1 draw until first set pixel.
A,B - variable A to Z. Filled with coordinates of last plotted pixel.
VLINE p,x1,y1,x2,y2,l,f,A,B
Same as HLINE, except l = y coordinate end pixel.
INK a
Draws in several colors.
a - color (0-15)
PAPER a
Selects background.
a - color (0-3)
MODE a
Select graphics mode, without clearing the screen.
a - resolution: 0= 64* 48 ( 0 )
1= 64* 64 color ( 1a )
2=128* 64 ( 1 )
3=128* 64 color ( 2a )
4=128* 96 ( 2 )
5=128* 96 color ( 3a )
6=128*192 ( 3 )
7=128*192 color ( 4a )
8=256*192 ( 4 )
BLOCK m,x,y,b,h
Draws a bar (solid filled rectangle).
m - plotting mode: 0=reset, 1=set, 2=invert.
x - x coordinate lower left corner,
y - y coordinate lower left corner,
b - width,
h - height.
SOUND p,d
Produces a sound according to:
p - pitch 1 [1..255]
d - duration [1..65535]
PAUSE t
Delays execution during t/60 seconds, t = [1..65535].
Pressing [Esc] exits the delay loop.
CREATE
Creates sprites and fillpatterns
-pattern
CREATE/P:n a1,a2,a3,a4,a5,a6,a7,a8
p - pattern number 0 to 31,
a - 8 bytes, from top row to bottom row.
-horizontal sprite
CREATE <name>,a1,a2,a3,...,a15,a16
CREATE/H <name>,a1,a2,a3,...,a15,a16
<name> - name of the sprite, maximum 8 characters,
/H - switch to define horizontal sprite (optional),
a1..a16 - sprite definition, according to the following table:
startposition -->| a8 | a16 |
| a7 | a15 |
| .. | ... |
| a2 | a10 |
| a1 | a9 |
-vertical sprite
CREATE /V <name>,a1,a2,a3,...,a15,a16
<name> - name of the sprite, maximum 8 characters,
/V - switch to define vertical sprite,
a1..a16 - sprite definition, according to the following table:
startposition -->| a16 |
| a15 |
| ... |
| a2 |
| a1 |
-auto assignment
CREATE/s <name>,a1,a2,a3,...,a15,a16/A:a
<name> - name of the sprite, maximum 8 characters,
/s - swithc to define sprite, horz or vert (H or V),
a1..a16 - sprite definition,
/A: - assign switch
a - assignment number (1 to 255, see ASSIGN).
DEF <name>,0/1..-16*-..0/1
DEF: 0/1..-16*-..0/1
Defines a horizontal sprite. A set pixel is defined as 1, a reset pixel
is defined as 0. For a complete sprite eight DEFs are required.
BASE q
Selects a memory block, where sprites and paint patterns will be stored
(together 2 kB). Also resets map-byte for INT and ATTRG.
q - high order byte of the start of the memory block.
ASSIGN:<name>,a
Assigns a number to a sprite. The sprite is then accessible through both
its name and its number.
<name> - name of the sprite,
a - assignment number [1..255].
DEASS:<name>
Disables the recognition of the sprite through an assignment number.
<name> - name of the sprite.
KILL:<name>
KILL a
Removes a sprite from the sprite administration.
<name> - name of the sprite,
a - sprite assignment number.
SET:<name>,x,y
SET a,x,y
Places a sprite on the screen.
<name> - name of the sprite,
a - sprite assignment number,
x - x position of the sprite,
y - y position of the sprite.
UNSET:<name>
UNSET a
Removes a sprite from the screen.
<name> - name of the sprite,
a - sprite assignment number.
IMAGE:<name>,x,y
IMAGE a,x,y
Same as SET, but now the sprite position is not stored in the sprite
administration.
<name> - name of the sprite,
a - sprite assignment number,
x - x coordinate of the sprite,
y - y coordinate of the sprite.
TURN:<name>
TURN a
Flips a horizontal or vertical sprite, on screen (if it's there) as well
as in the sprite administration.
<name> - name of the sprite,
a - sprite assignment number.
CARRY:<name>,x,y
CARRY a,x,y
Moves a sprite on screen (if it's there) to a new position.
<name> - name of the sprite,
a - sprite assignment number,
x - x coordinate of the sprite,
y - y coordinate of the sprite.
SHOVE:<name>,dx,dy
SHOVE a,dx,dy
Moves a sprite on screen, according to the entered displacements.
<name> - name of the sprite,
a - sprite assignment number,
dx - horizontal displacement,
dy - verticale displacement.
POS:<name>,A,B
POS a,A,B
Stores the coordinates of a certain sprite in the appropriate varables.
A - variable A to Z : x coordinate,
B - variable A to Z : y coordinate.
ATHIT:<name1>,<name2>
ATHIT:<name1>,a2
ATHIT a1,:<name2>
ATHIT a1,a2
Checks a sprite collision.
<name1> - name of sprite 1,
<name2> - name of sprite 2,
a1 - assignment number of sprite 1,
a2 - assignment number of sprite 2.
If the two sprites collide, the rest of the line is processed.
INT c,t (VIA required)
Offers the possibility to use 3 so called channels, that will be called
by the interrupts from timer 1 at specific times.
c - channel number 0, 1 or 2.
t - time [1..65535].
During declaration of INT, the rest of the line is treated as comment.
As soon as the desired time has elapsed, the statement that is being
processed by the interpreter will be finished, after which execution will
be continued at declaration-line right behind the parameters. The timer is
immediately disabled. The user must turn it on manually.
INT:p (VIA required)
Starts of stops the timer.
p - =0 : stop timer,
=1 : start timer.
Note the colons (:)
The timer runs at 50 Hz, which means the declared times must be multiplied
by 0.02. For 1 seconds, t=50.
ATTRG (VIA required)
(At Trigger) As INT, this is a declaration. If the timer is running and
the space bar or the fire button is depressed, the interpreter will finish
the current statement and will then jump to the first statement on the
ATTRG line behind the declaration.
Note: The interrupt handling uses a so called map-byte, which holds all
information on activated channels and ATTRG declarations. This
byte at address #0237 must be 0 at startup. This can be done through
BASE. If one doesn't use the BASE statement, this location must be
reset manually through: ?#237=0 or INT:0
Example:
10 INT:0
20 INT 0,100 P."TWO SECONDS ELAPSED"';GOTO a
30 INT 1,800 P."MAXIMUM RUN-TIME REACHED"';INT:0;END
40 ATTRG GOTO 100
50aINT:1
60 P."DO NOTHING"';GOTO 60
100 P."ALL IS OVER"';INT:0;END
Please note: This program can only be run once. If you want to run it
again, first press BREAK. The cause of this is that the interrupt vector
is not restored by GAGS2.2. If run a second time without a BREAK, the
program just keeps on going in circles.
Zero page usage:
5F - 60 temporary pointers for CREATE etc,
70 - 7F temporary usage,
021C - 021D counter channel 0,
021E - 021F wake-up time channel 0,
0220 - 0221 counter channel 1,
0222 - 0223 wake-up time channel 1,
0224 - 0225 counter channel 2,
0226 - 0227 wake-up time channel 2,
0228 - 0229 pointer channel 0,
022A - 022B pointer channel 1,
022C - 022D pointer channel 2,
022E - 022F pointer ATTRG,
0230 - 0233 window vectors,
0234 - 0235 plot vectors,
0236 window on/off,
0237 interrupt map-byte,
0238 - 0239 previous interrupt vector,
023A - 023C ink items,
023D - H.0 byte base
03F0 - 03F2 temporary bytes for INT and ATTRG
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