Consider a 3-year bond with face value of 100 that pays a fixed coupon of 3 percent issued on March 15, 2005.
Here is the same bond but using the ISDA convention.
Here is the interest accrued before the first coupon payment.
Compare this to
This shows the interest accrued right after the first coupon payment.
Here is the interest accrued two months after the first coupon payment.
Compare accrued interest and the difference between the clean price and the dirty price of a bond.