now i understand why the oscillations produced by the crystal need to be converted into a square wave,is it beacuse it uses a digital circuitary i.e 15 stage divide by 2 n/w . this means that we are making use of electronic circiut inside a watch so cant we produce the same resonant frequency of a crystal (32768 HZ) using a CMOS TIMER IC within a watch.
my question is then for what purpose is the crystal used ?

 

The crystal produces very very stable oscillations, so the watch may keep very accurate time.

 

sir but for the same purpose Can't CMOS 7555IC be used for generating 32768 hz which is cheap and also accurate moreover a 3vlithium cell can power the Cmos easily,isnt 't?
one more question which is the Cmos IC used for a 15stage /2 counter circuit

 

The 7555 / 555 is not the reference, it can be configured as an oscillator but uses an external resistor and capacitor for its time constant. R/C constants are quite inaccurate and also prone to frequency drift. The purpose of a watch is to keep reasonable time, therefore a crystal or some other accurate and stable timebase is still required.
The 4044 is a single 12 stage counter/divider, the 4020 is a single 14 stage, the 4060 is a single 14 stage with built in oscillator.

 

thank you very much sir

 

Go ahead and try the 555 as your square wave generator without the crystal. You might even build in both into the circuit and have jumpers or a switch to allow you to switch between them. This would be a good demonstration for other builders as to why you'd want to use a crystal.