1. <hardware, communications> (Or "beeper", "bleeper" (UK?)) A small wireless receiver that, when triggered (generally via phone), will beep or vibrate (un)pleasantly. The wearer will have been trained to respond to this signal by looking at a small screen on the device for an unimportant message.
In recent years, pagers have grown more complex, allowing for long alphanumeric messages to be received and scrolled though (as opposed to earlier models, which supported only short numeric messages); at the same time as pager functions are integrated into some PDAs. If this trend continues, the distinction between PDAs and high-end pagers will disappear.
Short Message Service allows a mobile phone to display a message, just like an alphanumeric pager.
2. <tool> A program for viewing a text file a screenful at a time via a text terminal, as opposed to scrolling through it in a GUI window, or catting it all at once to the terminal.