Zebra Keys Blog

Key signature has the sharp (^#), or flat (^b) signs placed at the beginning of the staff to indicate what key the music is played.
 
The 12 Keys in music are – 

C, D^b, D, E^b, E, F, F^#, G, A^b, A, B^b, B

 

Formula of major scale is –

Root + WS + WS + HS + WS + WS + WS + HS 
[WS – Whole Step, HS – Half Step]

In the key of C, the major scale is –

C, D, E, F, G, A, B, C

So, there is no sharps or flat in the key of C
[If you look in the diagram below, there are zero sharps or flats on the staff]
 
In the key of D, the major scale is –

D, E, F^#, G, A, B, C^#, D

So, there is 2 sharps and zero flat in the key of C 
[If you look in the diagram below, there are 2 sharps (F# and C#) with no flats on the staff]
 

 
 
You can also use the Circle of Fifths below to quickly find out how many sharps (#) or flats (b) in a certain key: