Please be aware that 7800basic cannot reliably add a variable to the score unless the variable is in Binary Coded Decimal format, or BCD for short. You can set the score variables with a regular assignment.Īnd any time you wish to change the score, just do so with a regular addition or subtraction operation. Usage of the score variables is straightforward.
Purebasic sprite maximum size free#
Variables, ensuring each dimension location has two free bytes of memory directly following it.ĭim score2=g : rem ** h and i are also used for score2 If you need more score variables than the two provided, you can dimension additional score2 to score9
Assuming playerx is a fixed point variable, the following example would silently generate incorrect code.ħ800basic provides you with two 24-bit score variables that you can use to track points for two player games, score0 and score1. Note : You must use decimal values when adding to fixed point variables. When it comes to other operations in 7800basic, like if…then statements, the language works with the variable by just referencing the “large” whole number part. The decimal point aspect of fixed point numbers is limited to addition and subtraction. This comes in handy, for example, when you want to move an object at slower speed than the frame rate. To use fixed point variables you need to name them with dim, but this time we tell 7800basic that we'll be representing the variable with 2 parts.Īfter that, using fixed point variables is pretty much as easy as using regular variables, except you can add or subtract values with a decimal point. 7800basic stores the integer part of the value in one byte, and the decimal part of the value in another. To use indirect arrays with those statements, you will need to assign any indirect array lookups to a variable, and use the variable with those statements.įixed point variables can be assigned fractional values, similar to floating point variables in other languages. Note : Many advanced statements in 7800basic don't work directly with indirect arrays. If your indirect array is accessing a data statement, you can forgo the constant definitions in the example above, and just add “_hi” and “_lo” to the data label name. Indirect variable arrays work with variable assignments and if…then statements. Rem ** An example of indirect variable array access. Rem ** Set the memory pointer to point to "mydata".
Rem ** Each data statement you wish to point at should To initialize the pointer to point to some data, you must use const to reference the data values…
Purebasic sprite maximum size code#
(The two bytes of memory must be dimmed to consecutive a-z memory locations.) This is typically used to access the advance POKEY sound registers, but you may also use indirect variable arrays if you wish to use the same code with different bits of data.Īn indirect variable array is signified by using double square braces around the array index. Indirect variable arrays are similar to regular variable arrays, but instead of accessing memory from a certain ROM or RAM location, they reference memory pointed to by a two-byte memory variable. The alternate formats 320C and 320D put odd limits where certain colors can be used, and as a consequence they're used less often than the other modes. 320A and 320B are also particularly useful and allow for higher resolution images. 320D requires pixels in odd columns to use the first two palette colors, and pixels in even columns to use the last two palette colors.Īs you can see from the table, the 160A/B mode has no restrictions, and is generally the most popular. In 320C mode, even pixel pairs use the first two colors in the palette, and odd pixel pairs use the last two colors in the palette.ģ20B mode requires pairs of pixels to use the same palette. See Joystick Controls, Driving Controls, Paddle Controls, Mouse Controls, Keypad Controls, SNES Controls, and Console Switches for more information. If you wish to support these switches in your game, you should check these switches during gameplay, and adjust difficulty as selected (A=pro, B=amateur). The Difficulty Switches can either be in A or B position. If pressed and released again, the game code should resume the action. If it's pressed and released, your game code should stop the action. If you wish to support in-game pausing, your game code needs to check this switch every frame. The Power button is a hardware switch that can't be detected or otherwise interacted with through software. The 7800 console itself has a number of switches on the console: Power, Pause, Reset, Player 1 Difficulty A/B, and Player 2 Difficulty A/B. The console can also be used with other legacy Atari controls, such as paddle controls, driving controls, and keyboard controls. The 7800 comes with 2 dual-button joysticks, though the console is often used with Atari single button joysticks as well.
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