Slow computer work can be done by intercepting a hardware interrupt is generated on the system timer, called on each tick of the real time clock of the computer and follow the idle cycles.
Stay resident in memory the program can function using the appropriate DOS. Also, using DOS functions can be performed and unloading of resident memory, first restore the interrupt vector intercepts. If you try to re-download the program may find itself in the memory by scanning the memory to search for the signature of the moderator or by setting the multiplex interrupt handler and restart it to cause an interrupt, and if a response is received from "our" handler, do not produce reloading.
To allow users to specify the command line modes moderator in the program should handle the command line, that is, by scanning to determine if there is a key, preset mode.
Processing hotkeys can be as follows: when you start the program will install its own vector processor hardware interrupt generated by the keyboard. This handler will have to verify the keys pressed, then the handler must perform a corresponding keyboard shortcuts: To change the delay, disable retarder. If a key combination is not provided by any action, management must be transferred to the "old" handler.
Indication of the degree of deceleration in percent can be achieved by converting the number of percent in a row and then writing it directly to video memory.