Write a brief summary of each of the four sections of Justinian's Code.

Justinian's code, also referred to as Code of Justinian or Codex Justinianus, is the collection of fundamental laws and legal interpretations, gathered by the order of Justinian I, Eastern Roman Emperor. It has four following sections:

1. Codex Constitutionum: it is a compilation of laws, rulings and imperial enactments issued by the emperors.

2. Digesta, or Pandectae: it is a collection of juristic writings, covering the trials and decisions.

3. Institutiones: a basic law textbook for students and lawyers.

4. Novellae Constitutiones Post Codicem: known as 'Novels' in English, it was a collection of newly proposed laws by the emperor.