In an isobaric process the pressure is kept constant (i.e. $$\Delta p=0$$). The work done by the gas is given by $$p\Delta V$$.
The change in internal energy during an isobaric process is given by $$\Delta U=Q-p\Delta V$$.
The p-V graph of an isobaric process is a horizontal line.
$$p=$$pressure; $$Q=$$heat supplied; $$T=$$temperature; $$\Delta U=$$change in internal energy; $$V=$$volume; $$W=$$work done