A single bit is useful if exactly two answers to a question are possible. Examples include the result of a coin toss (heads or tails), the gender of a person (male or female), the verdict of a jury (guilty or not guilty), and the truth of an assertion (true or false). Most situations in life are more complicated. This section concerns ways in which complex objects can be represented not by a single bit, but by arrays of bits.
Some objects for which codes may be needed include:
• Letters:, EBCDIC, ASCII, Unicode, Morse Code
• Integers: Binary, Gray, 2’s complement, BCD
• Numbers: Floating-Point
• Proteins: Genetic Code
• Telephones: NANP, International codes
• Hosts: Ethernet, IP Addresses, Domain names
• Images: TIFF, GIF, and JPEG
• Audio: MP3
• Video: MPEG
The first question to address is the number of symbols that need to be encoded. This is called the symbol space size. We will consider symbol spaces of different sizes:
• 1
• 2
• Integral power of 2
• Finite
• Infinite, Countable
• Infinite, Uncountable
In many situations there are some unused code patterns, because the number of symbols is not an integral power of 2. There are many strategies to deal with this. Here are some:
• Ignore
• Map to other values
• Reserve for future expansion
• Use for control codes
• Use for common abbreviations
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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