Notation for a whole note is a small oval that sits on a space or line on a musical staff. In 4/4 time signature (four beats per measure and quarter note gets one beat), whole notes carry four beats per measure.
Notation for a half note looks like the English letters "p" and "d" with longer stems. In 2/4, 3/4 and 4/4 time signatures, half notes account for two beats each. In the 6/8 time signature (eighth note gets one beat), each half note holds for four beats.
A quarter note is a half note with the circle center solidly filled in. In 2/4, 3/4 and 4/4 time signatures, quarter notes are worth one beat each. Beats are doubled in the 6/8 time signature, with quarter notes holding two beats.
Dotted half notes are held for three beats in 3/4 and 4/4 time signatures and six beats in the 6/8 time signature. Dotted quarter notes are worth 1 1/2 beats in 2/4, 3/4 and 4/4 time signatures and three beats in the 6/8 time signature.
Eighth notes are quarter notes with a flag or curved tail attached to the line. Consecutive eighth notes are notated as quarter notes with a horizontal line connecting all eighth notes. Each is worth half of one beat in 2/4, 3/4 and 4/4 time signatures. Eighth notes are worth one beat each in 6/8 time signature.