While the physical book is available for purchase on retailers like Amazon India, digital versions and study notes are often sought online: Information Theory and Coding by Giridar | PDF - Scribd
The average information per symbol of the source is Entropy ($H(X)$): $$H(X) = - \sum_i p(x_i) \log_2 p(x_i)$$ information theory and coding by giridhar pdf