Well, there are 3 exercises (Saju Jirugi, Saju Maki, and Saju Tolky - four direction punch, block and thrust, respectively) and 24 +1 tuls in the Ch'ang H'on tul set. By 24 +1, I mean that Gen. Choi intended there to be 24 patterns:
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Here I leave Taekwon-Do for mankind as a trace of man of the late 20th century. The 24 patterns represent 24 hours, one day, or all my life. The name of the pattern, the number of movements, and the diagrammatic symbol of each pattern symbolizes either heroic figures in Korean history or instances relating to historical events.
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[FONT=Verdana, Helvetica, Arial, Sans Serif]General Choi, Hong Hi[/FONT]
Ch'on-Ji
Dan-Gun
Do-San
Won-Hyo
Yul-Gok
Joon-Gun
Toi-Gye
Hwa-Rang
Choong-Mu
Kwan-Gae
Po-Eun
Ge-Baek
Eui-Am
Choon-Jang
Juche
(Ko-Dang)
Sam-Il
Yoo-Sin
Choi-Yong
Ul-Ji
Moon-Moo
So-San
Se-Jong
Tong-Il
Now, you will notice that there are 25 tuls in this list... the 25th, Ko-Dang, is in parenthesis because it is a historical revenant; it was replaced by Juche in the mid-80s as part of the attempt to have the ITF, rather than the WTF, in the Olympics. We still teach it because it is part of the history of our art - so technically there are 25 tuls, even though there are only supposed to be 24, as shown in the quote above.
Tuls are learned 1 per rank from 9th gup through 1st gup (Ch'on-Ji through Choong-Mu), then 3 per rank from I Dan to IV Dan (plus Ko-Dang, which is learned at II Dan), then 2 for V Dan, and finally 1 for VII Dan.
The 4 direction exercises listed above are not considered tuls, and tend to be used as training devices; they are short (7, 8, and 4 movements each, respectively) and, being exercises, can be modified in any fashion. The first two are learned by 10th gups; the third is learned by 2nd gups; there are other exercises learned at different ranks as well, but these three are more likely to be considered a type of pattern than the others.