1. A variable order short-term predictor of an encoder based on MPEG-4 Audio Lossless coding (ALS) standard, the variable order short-term predictor comprising: a pre-decision module receiving a prediction order for deciding the number of iterations of a filtering operation to calculate a modified prediction order for deciding the number of modified iterations of the filtering operation; a loop controller outputting a control signal for deciding the number of modified iterations according to the modified prediction order; an FIR filter receiving a sample signal, and iteratively performing the filtering operation on the sample signal; and an output module receiving the control signal and the filtered sample signal, holding an output of the FIR filter according to the control signal when the number of modified iterations is completed, and adding a filtering operation result, obtained per modified iteration number, while the output of the FIR filter is being held to output a finally filtered sample signal according to the control signal.