Since the Reagan administration took office, there have been three instances in which most, if not all, of the executive branch faced the prospect of a shutdown. Here's a summary provided by the Office of Management and Budget and the House Appropriations Committee.

* 1981: After President Reagan vetoed the second continuing resolution for fiscal 1982 on Nov. 23, the government shut down that day.

(The only appropriations bill that had passed covered the legislative branch.) The House and Senate immediately passed a new bill, which the president signed that day.

* 1982: A shutdown was threatened when Congress adjourned on Friday, Sept. 29, without passing a continuing resolution to fund most agencies for the first few weeks of fiscal 1983. (Again, only one appropriations measure had passed--the one covering the Housing and Urban Development Department and certain independent agencies.) After Reagan said he would sign the measure on Monday, Oct. 2, employes reported to work. (The resolution wasn't signed, however, until Oct. 3.)

* 1982: The first continuing resolution was to expire on Dec. 21. That night, Congress completed action on a measure to fund the agencies through the end of the fiscal year, and Reagan agreed to sign it, averting a shutdown. Until then, only bills covering HUD and the Transportation and Agriculture departments had passed. Congress also had passed the Interior bill, but Reagan didn't sign it until Dec. 30.