thanks in advance , i want to know how the pwm modulation of pifm works more precisely why the size of the buffer of data to be read in each iteration is 1024 bytes and how this buffer pcm data could be modulated into pwm signals , and if it is possible to have the same work done using wiringPi to control gpio pwm pin(c language) ??
I can answer the last part of the question (I suggest you Google for answers to the others).
No, you can't have "the same work done using wiringPi to control gpio pwm pin(c language) ?".
PiFM programs the PWM peripheral at a low level unsupported by wiringPi. The later invocations of PiFM also use DMA which is again unsupported by wiringPi.