Traders tend to think of bonds in terms of their clean prices.
The investor receives a $25 coupon payment every six months until the maturity date.
The bond price quoted to investors is $980 plus the accrued interest.
If the bond's last coupon payment was made on 1 June, on 1 September, the dirty price is: Clean Price + Accrued Interest (where accrued interest is the interest accumulated from 1 June to 31 August on the bond according to its coupon rate.)
The price changes continuously, as it depends on how many days have passed since the last coupon payment on the bond.