All the bonds are not making periodic coupon payments.

Zero-coupon bonds are those bonds where the bondholder realizes interest by buying it at a deep discount to its face value. Interest is then paid at the maturity date, with the interest being the difference between the par value and the price paid for the bond. One of the advantages of these bonds is that they are free of reinvestment risk, though the downside is that there is no opportunity to enjoy the effects of a rise in market interest rates. These bonds tend to be very sensitive to changes in interest rates.

Accrual bonds are a type of zero-coupon bonds that have contractual coupon payments which are accrued and distributed along with the maturity value at the maturity date.