In general, each Z -1 element in the filter structure creates a pole in the response. Thus an FIR uses no feedback, is inherently stable and will not oscillate. This allows the potential for oscillation and thus such filters are not inherently stable. The choice of an FIR design versus an IIR can spark much debate among designers. It is the opinion of the author that new users of digital filters should start out with FIR type filters.
Additional stages add to memory requirements and slow processing speed.
Designs that demand high performance usually justify an effort to trade off FIR vs IIR filter implementations. But for first time application it is recommended that aggressive filter design be avoided until one has the experience to avoid the various pitfalls that await you. From this information, compute the coefficients necessary. Create a matching array to hold the coefficients. A circular buffer works well for this purpose.