General purpose calculator with capability for performing yield-to-maturity of a bond calculation

An electronic calculator for calculating the yield to maturity of a bond having a maturity period, a bond price and a coupon rate, said calculator comprising:

• a first register for initially storing a first number representing the coupon rate divided by the bond price multiplied by a first selected value;
• a second register for initially storing a second number representing the inverse of the bond price multiplied by a second selected value;
• a third register for storing a third number having a magnitude greater than one and representing the normalized value of days in the maturity period;
• a fourth register for initially storing the contents of the first register;
• a fifth register for storing the results of calculations;
• a first means coupled to the first, second, third, and fourth registers for combining the contents thereof in accordance with the relation ##EQU1## where R is the contents of the fourth register, N is the contents of the third register, P is the contents of the second register, and K is the contents of the first register, said first means being coupled to the fifth register for storing the result of this combination therein;
• flag means, coupled to the third register, having set and reset states for indicating when the interest portion of the bond yield has been calculated;
• said flag means being set when the accrued interest portion of the bond yield has been calculated;
• said flag means being reset in response to the contents of the third register when those contents are greater than a third selected value;
• second means coupled to the fourth and fifth registers for subtracting the contents of the fifth register from the contents of the fourth register and for storing the difference in the fourth register, said last-stored contents of the fourth register representing the calculated yield to maturity of the bond;
• accruing means coupled to the first means and the first, second, third, and fourth registers for calculating an accrued interest portion of the bond price, for adjusting the contents of the first and second registers to account for the accrued interest portion of the bond price, and for thereafter causing the first means to combine the contents of the third register and the last-stored contents of the first, second, and fourth registers in accordance with said relation and store the result of this combination in the fifth register;
• third means, coupled to the flag means and responsive to the contents of the fifth register, for initiating operation of the accruing means when those contents are less than a fourth selected value and when the flag means is in the reset state;
• and
• output means coupled to the fourth and fifth registers and to the flag means for providing a visual output indication of the contents of the fourth register in response to the contents of the fifth register when the contents of the last-mentioned register are less than the fourth selected value and when the flag means is in the set state.