COS 100: Introduction to Programming

Fall 2019

Lab 13: Binary numbers

Lab 13A: Binary to decimal

• Write a function bin2dec that converts a binary number to decimal.
• The input is a binary number represented as a string consisting of 0s and 1s.
• Convert the binary number to decimal, returned as an integer.
• It's okay if your function only works on 8-bit (8-digit) binary numbers (corresponding to integers between 0 and 255).
• (Bonus) Make the function work on binary numbers of any length, not just of length 8.

• for num in ["01001001", "00010011", "00010000", "01100100", "100101100", "1011100001100"]:
      print(num, "in decimal is", bin2dec(num))
  

  01001001 in decimal is 73
  00010011 in decimal is 19
  00010000 in decimal is 16
  01100100 in decimal is 100
  100101100 in decimal is 300
  1011100001100 in decimal is 5900
  

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Lab 13B: Decimal to binary

• Write a function dec2bin that converts decimal to binary.
• The function accepts as input an integer between 0 and 255. (If a number outside this range is given, complain and quit.)
• Convert the number into an 8-bit binary number, returned as a string (so as to preserve the leading 0s).

• for num in [73, 19, 16, 100, 300]:
      print(num, "in binary is", dec2bin(num))
  

  73 in binary is 01001001
  19 in binary is 00010011
  16 in binary is 00010000
  100 in binary is 01100100
  300 is not between 0 and 255.  Bye.
  

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Challenge Lab 13C: Backwards binary

• Write a program that takes in a decimal integer and prints out the decimal integer you would get if you reversed the binary representation (ignoring leading zeros).
• For example:

  17 in binary is 10001 and its reverse is 10001 which is decimal 17
  34 in binary is 100010 and its reverse is 010001 which is decimal 17
  237 in binary is 11101101 and its reverse is 10110111 which is decimal 183
  16 in binary is 10000 and its reverse is 00001 which is decimal 1