Course Material

Weeks 1: Lectures

Introduction to Computers


Binary System

Decimal to Binary

Storing Characters

Steganography Example - Practice

Decimal/Binary Converter

Wolfram|Alpha: Computational Knowledge Engine

Decimal ASCII Chart

Material for Mini Quiz 1 Friday Sept 4

  • Conversion from decimal to binary (two methods)
  • Conversion from binary to decimal
  • Encoding short word (2-3 letters) into binary. Explain ONE letter in detail.
  • Decoding short binary sequence into sequence of characters (3-4 letters). Explain ONE BYTE in detail.

    Mini Quiz 1 Structure

    Exampes

    1. Convert binary number 1100 1101 to decimal
      Solution: add power of 2 that corresponds to the bits that are ON ( bits that are equal 1):
      128 + 64 + 8 + 4 + 1 = 205

      Final answer: 205 is decimal equivalent of binary number 1100 1101

    2. Convert decimal 38 to binary:
      Solution Method 1:
      128 fits into 38? NO b7 = 0
      64 fits into 38? NO b6 = 0
      32 fits into 38? YES b5 = 1
      38 - 32 = 6
      Continue with 6:
      16 fits into 6? NO b4 = 0
      8 fits into 6? NO b3 = 0
      4 fits into 6 YES b2 = 1
      6 - 4 = 2
      Continue with 2:
      2 fits into 2? YES b1 = 1
      2-2 = 0
      Continue with 0:
      1 fits into 0? NO b0 = 0

      Final answer: Decimal number 38 in binary is 0010 0110

      Method 2 using Integer Division and Remainder:
      38 / 2 = 19 remainder 0 b0 = 0
      19 / 2 = 9 remainder 1 b1 = 1
      9 / 2 = 4 remainder 1 b2 = 1
      4 / 2 = 2 remainder 0 b3 = 0
      2 / 2 = 1 remainder 0 b4 = 0
      1 / 2 = 0 remainder 1 b5 = 1
      As soon as we got 0 the process is stopped and the rest of the bits are 0: b6 = 0, b7 =0

      Final Answer: Decimal number 38 in binary system is: 0010 0110

    3. Convert binary number 0100 0100 to decimal
      Solution: add power of 2 that corresponds to the bits that are ON ( bits that are equal 1):
      64 + 4 = 68

      Final answer: 68 is decimal equivalent of binary number 0100 0100

    4. Convert decimal 121 to binary:
      Solution Method 1:
      128 fits into 121? NO b7 = 0
      64 fits into 121? YES b6 = 1
      121 - 64 = 57
      Continue with 57
      32 fits into 57? YES b5 = 1
      57 - 32 = 25
      Continue with 25:
      16 fits into 25? YES b4 = 1
      25 - 16 = 9
      Continue with 9
      8 fits into 9? YES b3 = 1
      9 - 8 = 1
      Continue with 1
      4 fits into 1? NO b2 = 0
      2 fits into 1? NO b1 = 0
      1 fits into 1? YES b0 = 1

      Final answer: Decimal number 121 in binary is 0111 1001

      Method 2 using Integer Division and Remainder:
      121 / 2 = 60 remainder 1 b0 = 1
      60 / 2 = 30 remainder 0 b1 = 0
      30 / 2 = 15 remainder 0 b2 = 0
      15 / 2 = 7 remainder 1 b3 = 1
      7 / 2 = 3 remainder 1 b4 = 1
      3 / 2 = 1 remainder 1 b5 = 1
      1 / 2 = 0 remainder 1 b6 = 1
      As soon as we got 0 the process is stopped and the rest of the bits are 0:b7 =0

      Final Answer: Decimal number 121 in binary system is: 0111 1001

    5. Convert Go! to binary
      Solution: Go! in ASCII is: 71 111 33
      71 to binary:
      71/2 = 35 b0 = 1
      35/2 = 17 b1 = 1
      17/2 = 8 b2 = 1
      8/2 = 4 b3 = 0
      4/2 = 2 b4 = 0
      2/2 = 1 b5 = 0
      1/2 = 0 b6 = 1
      71 in binary: 0100 0111
      111 in binary: 0110 1111
      33 in binary: 0010 0001

      Final answer: Go! in binary: 01000111 01101111 00100001

    6. Decode: 01101101 01000101 00110010
      Solution: converting each BYTE to decimal
      0110 1101 adding powers of 2 that are ON: 64 + 32 + 8 + 4 + 1 = 109
      0100 0101 is 69
      0011 0010 is 50
      Original message in ASCII 109 69 50

      Final answer: decoded word: mE2


      Programming with Python

      Online Resource

      Input and Formatted Output in Python:

      • For integers use: int(input("user prompt "))

      • For floats use: float(input("user prompt "))

      • For strings use: input("user prompt ") and when inputing the string you must enclose it in double or single quotes

      • For formatted output use function format.

        • For example, to print only 2 decimal digits of the number 1232.566777 use the following statement:

          print(format(1232.566777, '.2f'))

        • For example, to print only 4 decimal digits of the number 1232.566777 use the following statement:

          print(format(1232.566777, '.4f'))