The popmessage() function is used to display on-screen info at the bottom of the emulated display.

Declared in src/emu/mame.h as

void CLIB_DECL popmessage(const char *format, ...) ATTR_PRINTF(1,2);

• *format – Pointer to a const char with the text to be printed. Supports printf-style parameters. Can be NULL, in this case the displayed message is cleared immediately.
• … – A list of variables that are referenced in the text.

Nothing.

popmessage("IOC IRQ status - %02x", sys.ioc.irqstatus);

Will output

IOC IRC status - 03

on the screen.

• logerror()