Chapter 2, Problem 39E

Program Plan Intro

Octal subtraction:

The rules for subtracting two octal numbers are as follows:

• Read both the numbers to know the number of bits.
• If the number of bits in the first number is less than that of the other number, add the required number of zeros on the left side.
• Numbers are represented in bytes where one byte is equal to 8 bits.
• Align the number in correct order after padding. The octal number that is followed by a minus sign should be subtracted from the other octal number.

Explanation of Solution

b.

“1234 – 765”:

• Start numbers from right to left.
  • Subtract “5” from “4”.
    • Here “4” is less than “5”. As a result, borrow a number from adjacent left hand side.
    • After borrowing it becomes “2” as adjacent left side number is “3”.
    • After borrowing, add “8” with “4”.
    • Add “8” with “4” and then subtract it from “5”, which give “7”. The equivalent octal number for number “7” is “7”. Hence, write “7” to the result.
  • Subtract “6” from “2”.
    • Here “2” is less than “6”. Borrow number from adjacent left side.
    • After borrowing, it becomes “1” as adjacent left side number is “2”.
    • After borrowing, add “8” with “2”.
    • Add “8” with “2” and then subtract this from “6”, which give “4”...

Explanation of Solution

c.

“7766 – 5544”:

• Start with the numbers from right to left.
  • Subtract “4” from “6” which results in “2”.
  • Subtract “4” from “6” which results in “2”.
  • Subtract “7” from “5” which results in “2”...