The memory unit in a digital computer performs the storage function. It must provide means of access for the retrieval or readout, and alteration or write-in, of selected portions of the stored information
Boolean algebra permits only two values or states for a variable. In logic, these two states represent 'true' and 'false' and in circuits they represent 'on' and 'off' or the 'cutoff' and 'saturation' state of Boolean of an electronic device.
A multivibrator which generates square waves of its own (i.e without any external trigger pulse) is known as astable multivibrator. It is also called free ramming multivibrator. It has no stable state but only two quasi-stable (half-stable) makes oscillating continuosly between these states.
In a monostable multivibrator, one of the state is absolutely permanent i.e, stable and the other one is temporary i.e, quasi-stable. collector coupled,emitter coupled, OP-AMP, and 555 timer IC Monostable multivibrators
A 555 timer IC is used a a-stable multivibrator as shown in the given figure (A). The threshold input is now connected to the trigger input (Pin 2), the resister R1, R2 and capacitor C1 for timing network which set the frequency of the oscillator.