Roll call is taken at the start of every day. It is taken again after breaks.
The chair reads out the delegations. Each delegate answers when their delegation is called.
There are three states a delegation can be in.
Present. The delegate may vote in favour, against, or abstain.
Present and voting. The delegate may vote in favour or against. They cannot abstain.
Absent. The delegate cannot vote.
A delegate answers "present" or "present and voting". Absent is not something a delegate says. It is what the chair records when nobody answers for that delegation.
One delegate answers for each delegation.
For what present and voting commits you to, see Present and voting.
In MEDIMUN, one delegate represents one country in a committee. THIMUN seats two delegates on one country in some of its forums. MEDIMUN does not do this.
In MEDIMUN, all roll calls are taken in MediBook. The roll call is what sets who can vote. See Committee roll calls and Chair roll calls.
SCREENSHOT: /medibook/sessions/22/committees/ga1/debate/control - the roll call, with delegations marked present, present and voting, and absent
The roll call does two things at once.
It establishes quorum, which is the number of delegations that have to be present before the committee can open debate or take a decision.
It sets voting eligibility. A delegation marked absent cannot vote, whatever happens later in the debate. See Who may vote.
If a delegate arrives after the roll call. They must tell the chairs. If they do not, the chairs should ask them for an explanation. A delegation that is in the room but recorded as absent is a problem for every vote that follows.
If you are unsure. Take the roll call again rather than correct it from memory. It is faster than working out which delegations have changed state since the morning, and the record is then one you can rely on.
In MEDIMUN, if any delegates are missing under the missing delegate policy, the chair tells the secretariat immediately, using the MediBook feature for it. See the Missing delegate policy.