Hi Uday,

Hope you are doing great.

As you asked, The shape of Graph of carnot cycle in T-S diagram is a Rectangle. Carnot cycle can be represented in T-S diagram,with T along y-axis and S along x-axis. This cycle is a reversible cycle in state space of thermodynamic system.

If you are willing to know more information about Carnot cycle refer the books (thermodynamics).

Hope this is enough.