Note 1.a. The ukulele is like the first four strings of a guitar capoed at the fifth fret!

The notes on the first four strings of a guitar are (D,G,B,E).
The notes on the first four strings of a ukulele are (g,C,E,A).

1. The notes on the first four strings of the guitar capoed at the first fret are (D#,G#,C,F).
2. The notes on the first four strings of the guitar capoed at the second fret are (E,A,C#,F#).
3. The notes on the first four strings of the guitar capoed at the third fret are (F,A#,D,G).
4. The notes on the first four strings of the guitar capoed at the fourth fret are (F#,B,D#,G#).
5. The notes on the first four strings of the guitar capoed at the fifth fret are (G,C,E,A).

The only difference is the ukulele's reentrant tuning, that is, the ukulele's 4-th string 'g' is an octave above the guitar's 4-th string 'G'.

This means that chord shapes formed on the first four strings of a guitar are also ukulele chords, but with different names. For example, the D chord on a guitar becomes a G chord on the ukulele, that is, a D chord moved up five frets (D=0,Eb=1,E=2,F=3,F#=4,G=5). The same holds true for any other guitar chords one might know. Guitar players can be confident that much of what they know carries over to the ukulele.