A real time clock alarm is a feature that can be used to allow a computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 to 'wake up' after shut down to execute tasks every day or on a certain day. It can sometimes be found in the 'Power Management' section of a motherboard

Motherboard

In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...

's BIOS

BIOS

In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....

 setup. However, newer BIOS setups do not include an RTC alarm option, although it can still be set from within user applications. Wake On LAN, Wake on ring

Wake-on-ring

Wake-on-Ring , sometimes referred to as Wake-on-Modem , is a specification that allows supported computers and devices to "wake up" or turn on from a sleeping, hibernating or "soft off" state Wake-on-Ring (WOR), sometimes referred to as Wake-on-Modem (WOM), is a specification that allows supported...

, and IPMI

Intelligent Platform Management Interface

The Intelligent Platform Management Interface is a standardizedcomputer system interface used by system administrators to manage a computer system and monitor its operation....

 functions could also be used to start a computer after it is turned off.

In Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

, the real time clock alarm can be set or retrieved using /proc/acpi/alarm or /sys/class/rtc/rtc0/wakealarm.

In Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 there are different programs which could be used to 'wake up' a computer from standby or hibernation. Task Scheduler

Task Scheduler

Task Scheduler is a component of Microsoft Windows that provides the ability to schedule the launch of programs or scripts at pre-defined times or after specified time intervals. It was first introduced in the Windows 95 Plus! pack as System Agent but was renamed to Task Scheduler in Windows 98...

 settings for power management can be used to 'Wake the computer to run this task'.

See also

• Alert on LAN
  Alert on LAN
  Alert on LAN is a 1998, IBM- and Intel-developed technology that allows for remote management and control of networked PCs. AOL requires a Wake on LAN adapter.- Technical details :...
  
  
• Wake-on-Ring
  Wake-on-ring
  Wake-on-Ring , sometimes referred to as Wake-on-Modem , is a specification that allows supported computers and devices to "wake up" or turn on from a sleeping, hibernating or "soft off" state Wake-on-Ring (WOR), sometimes referred to as Wake-on-Modem (WOM), is a specification that allows supported...
  
   (WOR)
• Wired for Management
  Wired for Management
  Wired for Management was a primarily hardware-based system allowing a newly built computer without any software to be manipulated by a master computer that could access the hard disk of the new PC to paste the install program. It could also be used to update software and monitor system status...
  
  
• Wake on LAN