Returning YES/NO conditionally

Question

I have a table for recording maintenance actions on large ships. The table has a "task_number" column (a code to identify the task) and a "task_class" column which refers to each ship type (small, medium or large ships, for instance). The task numbers are not the PK, and there are duplicates. Each record contains the task number, task class, and more associated information. The task number and task class are never null. I would like to run a query that would return something like this:
If the table contained data such as
TASK_NUMBER | TASK_CLASS
X-3161-0 | SMALL
X-3161-0 | LARGE
X-1984-3 | LARGE
P-3535-1 | MEDIUM
P-3535-1 | SMALL
P-3535-1 | LARGE
TASK_NUMBER | SMALL? | MEDIUM? | LARGE?
X-3161-0 | YES | NO | YES
X-1984-3 | NO | NO | YES
P-3535-1 | YES | YES | YES
So, as you can see, every task number should be included, and then the class applicability follows. I do know ahead of time what all of the "classes" are--I don't have to figure that out at run time.
If this can be done easily with plain SQL, I would appreciate it, but PL/SQL is acceptable too.

Answer 1

As requested, here are the CREATEs and INSERTs. Although, I think the last posts may have answered the question. I'll be giving it a try in a bit.
Thanks for all the help!
CREATE TABLE ship_class
          equipment_id      VARCHAR2(5)     NOT NULL,
          task_nr               NUMBER(3,0)     NOT NULL,
          task_nr_rev          NUMBER(3,0),
          freq                NUMBER(3,0)     NOT NULL,
          man_days           VARCHAR2(5)     NOT NULL,
          class               VARCHAR2(15)     NOT NULL,
          mat_cost_est      NUMBER(6,0)     NOT NULL
CREATE TABLE equipment_id
          equipment_id     CHAR(5) NOT NULL,
          equip_NM          VARCHAR2(65)NOT NULL
CREATE TABLE task_detail
          equipment_id     CHAR(5)     NOT NULL,
          TASK_NR               NUMBER(3,0)     NOT NULL,
          TASK_NR_REV          CHAR(1)     NOT NULL,
          RMRK               VARCHAR2(4000)     NOT NULL,
          TASK_ABRVTN          VARCHAR2(30)     NOT NULL,
          TASK_DC               VARCHAR2(1000)     NOT NULL,
          TASK_TYPE          CHAR(1)     NOT NULL
     INSERT INTO ship_class (equipment_id, task_nr, task_nr_rev, freq, man_days, class, mat_cost_est) VALUES
     ('3161', '0', 'A', 24, 10, 'small', 100);
     INSERT INTO ship_class (equipment_id, task_nr, task_nr_rev, freq, man_days, class, mat_cost_est) VALUES
     ('3161', '0', 'A', 24, 10, 'large', 1000);
     INSERT INTO ship_class (equipment_id, task_nr, task_nr_rev, freq, man_days, class, mat_cost_est) VALUES
     ('1984', '3', 'A', 24, 10, 'large', 75);
     INSERT INTO ship_class (equipment_id, task_nr, task_nr_rev, freq, man_days, class, mat_cost_est) VALUES
     ('3535', '1', 'A', 24, 10, 'large', 500);
     INSERT INTO ship_class (equipment_id, task_nr, task_nr_rev, freq, man_days, class, mat_cost_est) VALUES
     ('3535', '1', 'A', 24, 10, 'small', 100);
     INSERT INTO ship_class (equipment_id, task_nr, task_nr_rev, freq, man_days, class, mat_cost_est) VALUES
     ('3535', '1', 'A', 24, 10, 'medium', 250);
     INSERT INTO equipment_id (equipment_id, equip_nm) VALUES ('3161', 'FLUX CAPACITOR');
     INSERT INTO equipment_id (equipment_id, equip_nm) VALUES ('3535', 'STEAM NEUTRALIZER');
     INSERT INTO equipment_id (equipment_id, equip_nm) VALUES ('1984', 'TURBO ENCABULATOR');
     INSERT INTO task_detail (equipment_id, task_nr, task_nr_rev, rmrk, task_abrvtn, task_dc, task_type) VALUES
     ('3161', '0', 'A', 'This is a remark', 'ENRGZ FLUX CAP', 'Energize the flux capacitor', 'X');
     INSERT INTO task_detail (equipment_id, task_nr, task_nr_rev, rmrk, task_abrvtn, task_dc, task_type) VALUES
     ('1984', '3', 'A', 'This is a remark', 'CLBRT TRBO ENC', 'Calibrate the Turbo Encabulator', 'X');
     INSERT INTO task-detail (equipment_id, task_nr, task_nr_rev, rmrk, task_abrvtn, task_dc, task_type) VALUES
     ('3535', '1', 'A', 'This is a remark', 'TEST STM NTRLZER', 'Test the Steam Neutralizer', 'P');
I am hoping to create a table with TASK_IDs, which I usually create like this:
SELECT
     t.task_type || '-' || t.equipment_id || '-' ||
          TO_CHAR(t.task_nr, 'FM099') ||
          TRIM(BOTH ' ' FROM c.task_nr_rev) as TASK_ID,
Note that the TASK_ID is composed of parts from two different tables, t. and c.
So I will have the TASK_IDs followed by the task description, task abbreviation, equipment name, etc, and then YES's and NO's based on whether they apply to each ship class. So at the top, I would have SMALL, MEDIUM, and LARGE, with a bunch of YES's and NO's below them.
By the way, how do you guys post mono-spaced? I don't see the <code> tags are working here.