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Definitions on the following list are frequently provided by the default automatically-imported modules. 

However, as they are not the part of the standard library, they might not be available on all targets:

#### `void putchar(byte char)`

Prints a single character.

Available for: all computer targets.

#### `void new_line()`

Moves the cursor to the next line.

Available for: all computer targets.

#### `pointer readline()`

Reads a line from the console and returns a pointer to a null-terminated string.
The string is valid only until next read from the console.

Available for:
ZX Spectrum,
NEC PC-88,
Commodore 64 with `c64_basic` module,
Commodore 16 or Plus/4 with `c264_basic` module.

#### `word readword()`

Reads a 16-bit unsigned integer from the console.

Available for:
ZX Spectrum,
NEC PC-88,
Commodore 64 with `c64_basic` module,
Commodore 16 or Plus/4 with `c264_basic` module.

#### `void bell()`

Beeps.

Available for: Apple 2, ZX Spectrum.

#### `void set_bg_color(byte color)`

Sets the screen background color.

Available for: C64, VIC-20, C64, C264 series.

#### `void set_border(byte color)`

Sets the screen border color.

Available for: VIC-20, C64, C264 series, ZX Spectrum.

#### `const byte black, white, red, green, blue, cyan, purple, yellow`

Various colour constants.

Available for: VIC-20, C64, C264 series, ZX Spectrum.

#### `macro void memory_barrier()`

Informs the optimizer that at this point arbitrary memory has been accessed and either read or written by an external device.
The optimizer should not optimize any memory accesses across that macro.

Available for: all targets.