Explanation:

Unlike the question hour, the zero hour is not mentioned in the Rules of Procedure. Thus, it is an informal device available to the members of the Parliament to raise matters without any prior notice. The zero hour starts immediately after the question hour and lasts until the agenda for the day (ie, regular business of the House) is taken up. In other words, the time gap between the question hour and the agenda is known as zero hour. It is an Indian innovation in the field of parliamentary procedures.
Calling Attention Motion, it is introduced in the Parliament by a member to call the attention of a minister to a matter of urgent public importance, and to seek an authoritative statement from him on that matter. Like the zero hour, it is also an Indian innovation in the parliamentary procedure and has been in existence since 1954. However, unlike the zero hour, it is mentioned in the Rules of Procedure.
Do you know?
•A matter which is not a point of order or which cannot be raised during question hour, half-an hour discussion, short duration discussion or under adjournment motion, calling attention notice or under any rule of the House can be raised under the special mention in the Rajya Sabha. Its equivalent procedural device in the Lok Sabha is known as ‘Notice (Mention) Under Rule 377’.
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•Privilege Motion.