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Alphabet , String, and Language:

الكلية كلية العلوم للبنات     القسم قسم الحاسبات     المرحلة 2
أستاذ المادة زينب فلاح حسن الكيم       22/10/2019 17:35:53
Computations are designed for processing information. They can be as simple as estimation for driving time between cities, and as complex as a weather prediction.

1.1Alphabet , String, and Language:
The ability to represent information is crucial to communicating and processing information. Human societies created spoken languages to communicate on a basic level, and developed writing to reach a more sophisticated level.
The English language, for instance, in its spoken form relies on some finite set of basic sounds as a set of primitives. The words are defined in term of finite sequences of such sounds. Sentences are derived from finite sequences of words. Conversations are achieved from finite sequences of sentences, and so forth.
Written English uses some finite set of symbols as a set of primitives. The words are defined by finite sequences of symbols. Sentences are derived from finite sequences of words. Paragraphs are obtained from finite sequences of sentences, and so forth.
Similar approaches have been developed also for representing elements of other sets. For instance, the natural number can be represented by finite sequences of decimal digits.
Computations, like natural languages, are expected to deal with information in its most general form. Consequently, computations function as manipulators of integers, graphs, programs, and many other kinds of entities. However, in reality computations only manipulate strings of symbols that represent the objects.
2.1.1 An alphabet:
Is a finite, nonempty set of symbols. Its symbol is ?(sigma) for an alphabet.
Common alphabet include:
1. ?={0,1}, the binary alphabet.
2. ?={a,b,….,z}, the set of all lower-case letters.
3. The set of all ASCII character, or the set of all printable ASCII characters.
2.1.2 Strings:
A string is a finite sequence of symbols chosen from some alphabet.
For example: 01101 is a string from the binary alphabet ?={0,1}.
The string 111 is another string chosen from this alphabet.
1. The empty string: is the string with zero occurrences of symbols. This string denoted ?, is a string that may be chosen from any alphabet.


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 .