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## 5. Loadable drivers

## 5.1 Graphics drivers

Currently there are no graphics drivers available for the Atari platform. However, the runtime library provides a function named _graphics, with a mode parameter just like the BASIC GRAPHICS command. This function will switch to the requested graphics mode. There are currently no functions available to access the graphics memory. The access must be implemented manually.

Many graphics modes require more memory than the text screen which is in effect when the program starts up. Therefore the programmer has to tell the program beforehand the memory requirements of the graphics modes the program intends to use. This can be done by using the __RESERVED_MEMORY__ linker config variable. The number specified there describes the number of bytes to subtract from the top of available memory as seen from the runtime library. This memory is then used by the screen buffer.

The numbers for the different graphics modes presented below should only be seen as a rule of thumb. Since the screen buffer memory needs to start at specific boundaries, the numbers depend on the current top of available memory. The following numbers were determined by a BASIC program.

graphics mode | reserved memory
0 | 1
1 | 1
2 | 1
3 | 1
4 | 1
5 | 182
6 | 1182
7 | 3198
8 | 7120
9 | 7146
10 | 7146
11 | 7146
12 | 162
13 | 1
14 | 3278
15 | 7120
16 | 1
17 | 1
18 | 1
19 | 1
20 | 1
21 | 184
22 | 1192
23 | 3208
24 | 7146
25 | 7146
26 | 7146
27 | 7146
28 | 160
29 | 1
30 | 3304
31 | 7146

reserved memory required for different graphics modes

The values of "1" are needed because the graphics command crashes if it doesn't have at least one byte available. This seems to be a bug of the Atari ROM code.

## 5.2 Extended memory drivers

Currently there are no extended memory drivers available for the Atari platform.

## 5.3 Joystick drivers

`ataristd.joy`

  Supports up to four standard joysticks connected to the joystick ports of the Atari.

`atarim8.joy`

  Supports up to eight standard joysticks connected to a MultiJoy adapter.

## 5.4 Mouse drivers

Currently no drivers available (in fact, the API for loadable mouse drivers does not exist). There is a static driver you can use.

## 5.5 RS232 device drivers

Currently there are no RS232 loadable drivers available for the Atari platform. There is a static driver you can use.

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