These are otherwise called tonic sol-fahs.  They are basically 8 in number and they are:
These solfa notations have technical names and they are as follows:

Triad means chord built with thirds. A triad is a group of three notes played or sung together. It is a music theory term for a chord of three notes; it consist a root or first, a third and a fifth. We say that triads are built out of thirds, because the interval between the lowest note and the middle note is a third, and the interval between the middle note and the highest note is also a third.8
The following are guidelines in constructing a triad without inversions:
Draw the stave
Draw the clef
Insert the key signature if you’re meant to use key signature; if not, go to the next step
Draw the triad starting from the root except where asked to do otherwise.
Insert the accidental sign
Close the stave with a double bar line
Example: construct the tonic triad of D major on treble stave using accidental
The scale of G major is given as D E F G A B C D. The tonic is the first note of the scale. Since we’re in D major, the tonic is D. That is going to be the first note we write down. It’s going to be the lowest note of the triad, so we’ll write a low G, so that we have plenty of rooms to add notes above it.The next note in the triad is the third and the third note in the scale is F, so we add that one too.The last note in the triad is the fifth and the fifth note in the scale is A.

Here is our finished tonic triad of D major:

Note: when constructing a triad with key signature, you fix in the key signature before constructing the triad.

In grade one music theory, you might be asked to name the key of some tonic and dominant triads. This is very easy to do if you remember that the lowest note in the triad will give you the answer. You won’t be tested on minor triads and triad inversion so therefore if the lowest note is C, then the key will be C major, but make sure you pay attention to the clef and key signature. 

In grade one music theory, you might be asked to add a clef and a key signature to some tonic or dominant triad. You would be told the key of the triad. Look at the lowest note in the triad, and think about what that note would be with a treble clef and with a bass clef. In our example, if we had a treble clef, the note would be E. if we had a bass clef, the note would be G. we need a G so it must be a bass clef.