{"id":57077,"date":"2019-05-28T17:27:26","date_gmt":"2019-05-28T11:57:26","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=57077"},"modified":"2021-05-14T18:06:29","modified_gmt":"2021-05-14T12:36:29","slug":"tokens-in-c","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/tokens-in-c\/","title":{"rendered":"Tokens in C – An Awesome Concept you can\u2019t Afford to Miss Out"},"content":{"rendered":"

As we can’t construct a sentence without the use of words, similarly, we can’t construct a program without using building blocks. The smallest individual element in a program is a token. Without tokens, programming can’t be done in C. Generally, tokens in C is the basic component of creating source code.<\/p>\n

In this C tutorial, we will cover following topics:<\/p>\n

    \n
  1. Keywords in C<\/li>\n
  2. Identifiers in C<\/li>\n
  3. Strings in C<\/li>\n
  4. Operators in C<\/li>\n
  5. Constant in C<\/li>\n
  6. Special Characters in C<\/li>\n
  7. Quiz on above topics<\/strong><\/li>\n<\/ol>\n

    What are Tokens in C?<\/h2>\n

    Tokens in C language are the smallest possible unit of a program, that conveys a specific meaning to the compiler. It is the building blocks of a programming language.<\/p>\n

    Different Types of Tokens in C<\/h4>\n

    There are 6 types of Tokens in C programming languages-<\/em><\/p>\n

    \"Different<\/a><\/p>\n

    It is important to understand that these names can\u2019t be used interchangeably, hence, we will discuss each type of tokens in C in detail.<\/p>\n

    1. Keywords in C<\/h3>\n

    Keywords in C language are the pre-defined & reserved words, each having its own significance and hence has a specific function associated with it.\u00a0We can\u2019t simply use keywords for assigning variable names, as it would connote a totally different meaning altogether and would be erroneous.\u00a0There are a total of 32 keywords offered in C.<\/p>\n\n\n\n\n\n<\/colgroup>\n\n\n\n\n\n\n\n\n\n
    auto<\/td>\nbreak<\/td>\ncase<\/td>\nchar<\/td>\n<\/tr>\n
    continue<\/td>\ndo<\/td>\ndefault<\/td>\nconst<\/td>\n<\/tr>\n
    double<\/td>\nelse<\/td>\nenum<\/td>\nextern<\/td>\n<\/tr>\n
    for<\/td>\nif<\/td>\ngoto<\/td>\nfloat<\/td>\n<\/tr>\n
    int<\/td>\nlong<\/td>\nregister<\/td>\nreturn<\/td>\n<\/tr>\n
    signed<\/td>\nstatic<\/td>\nsizeof<\/td>\nshort<\/td>\n<\/tr>\n
    struct<\/td>\nswitch<\/td>\ntypedef<\/td>\nunion<\/td>\n<\/tr>\n
    void<\/td>\nwhile<\/td>\nvolatile<\/td>\nunsigned<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Key takeaway:<\/strong> All the keywords in C are lowercase in nature.<\/p>\n

    Apart from the above-listed keywords, there are certain supplementary words that cannot be used as variable names.\u00a0They are listed in alphabetical order as follows:<\/p>\n

      \n
    1. asm<\/li>\n
    2. bool<\/li>\n
    3. catch<\/li>\n
    4. class<\/li>\n
    5. const_cast<\/li>\n
    6. delete<\/li>\n
    7. dynamic_cast<\/li>\n
    8. explicit<\/li>\n
    9. export<\/li>\n
    10. false<\/li>\n
    11. friend<\/li>\n
    12. inline<\/li>\n
    13. mutable<\/li>\n
    14. namespace<\/li>\n
    15. new<\/li>\n
    16. operator<\/li>\n
    17. private<\/li>\n
    18. protected<\/li>\n
    19. public<\/li>\n
    20. reinterpret_cast<\/li>\n
    21. static_cast<\/li>\n
    22. template<\/li>\n
    23. this<\/li>\n
    24. throw<\/li>\n
    25. true<\/li>\n
    26. try<\/li>\n
    27. typeid<\/li>\n
    28. typename<\/li>\n
    29. using<\/li>\n
    30. virtual<\/li>\n
    31. wchar_t<\/li>\n<\/ol>\n

      2. Identifiers in C<\/h3>\n

      The C programmer has the provision to give names of his own choice to variables, arrays, and functions. These are called identifiers in C.\u00a0The user may use the combination of different character sets available in the C language to name an identifier but, there are certain rules to be abided by the user on his part when naming identifiers, otherwise the situation would prove to be dicey.<\/p>\n

      Rules for Identifiers in C –<\/strong><\/p>\n

        \n
      1. First character:<\/strong> The first character of the identifier should necessarily begin with either an alphabet or an underscore. It cannot begin with a digit.<\/li>\n
      2. No special characters:<\/strong> C does not support the use of special characters while naming an identifier. For instance, special characters like comma or punctuation marks can\u2019t be used.<\/li>\n
      3. No keywords:<\/strong> The use of keywords as identifiers is strictly prohibited, as they are reserved words which we have already discussed.<\/li>\n
      4. No white space:<\/strong> White spaces include blank spaces, newline, carriage return, and horizontal tab, which can\u2019t be used.<\/li>\n
      5. Word limit:<\/strong> The identifier name can have an arbitrarily long sequence that should not exceed 31 characters, otherwise, it would be insignificant.<\/li>\n
      6. Case sensitive:<\/strong> Uppercase and lowercase characters are treated differently.<\/li>\n<\/ol>\n

        Here is a table which illustrates the valid use of Identifiers in C:<\/strong><\/p>\n\n\n\n\n\n<\/colgroup>\n\n\n\n\n\n\n\n\n\n
        Identifiers Name<\/strong><\/td>\nValid or\u00a0 Invalid<\/strong><\/td>\nCorrection or Alternative, If Invalid<\/strong><\/td>\nElucidation, If Invalid<\/strong><\/td>\n<\/tr>\n
        20th_name<\/td>\nInvalid<\/td>\nname_20<\/td>\nIt violates Rule 1 as it begins with a digit<\/td>\n<\/tr>\n
        _age<\/td>\nValid<\/td>\n–<\/td>\n–<\/td>\n<\/tr>\n
        market.bill<\/td>\nInvalid<\/td>\nmarket_bill<\/td>\n\n
        \n
        It violates Rule 2 as it contains a special character \u2018.\u2019<\/div>\n<\/div>\n<\/td>\n<\/tr>\n
        delete[5]<\/td>\nInvalid<\/td>\ndelet[5]<\/td>\nIt violates Rule 3 as it contains a keyword<\/td>\n<\/tr>\n
        employee[10]<\/td>\nValid<\/td>\n–<\/td>\n–<\/td>\n<\/tr>\n
        customer name<\/td>\nInvalid<\/td>\ncustomername<\/td>\nIt violates Rule 4 as it contains a blank space<\/td>\n<\/tr>\n
        area()<\/td>\nValid<\/td>\n–<\/td>\n–<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        3. Constants in C<\/h3>\n

        Often referred to as literals, constants, as the name itself suggests, are fixed values i.e. they cannot change their value during program run once they are defined.<\/p>\n

        Syntax of Constant in C Programming-<\/strong><\/p>\n

        const data_type variable_name = value;<\/em><\/p>\n

        Various Types of Constants in C Language-<\/h4>\n
          \n
        1. Integer constants:<\/strong> These are of the integer data type. For example,\u00a0const int value = 400;<\/em><\/li>\n
        2. Floating constants:<\/strong> These are of the float data type. For example,\u00a0const float pi = 3.14;\u00a0<\/em><\/li>\n
        3. Character constants: <\/strong>These are of the character data type. For example,\u00a0const char gender = \u2018f\u2019;\u00a0<\/em><\/li>\n
        4. String constants:<\/strong> These are also of the character data type, but differ in the declaration. For example,\u00a0const char name[] = \u2018\u2018DataFlair\u2019\u2019;\u00a0<\/em><\/li>\n
        5. Octal constants:<\/strong> The number system which consists only 8 digits, from 0 to\u00a0 7 is called the octal number system. The constant octal values can be declared as,\u00a0const int oct = 040;<\/em> (It\u00a0is the octal equivalent of the digit “32” in the decimal number system.)<\/li>\n
        6. Hexadecimal constants:<\/strong> The number system which consists of 16 digits, from 0 to 9 and alphabets \u2018a\u2019 to \u2018f\u2019 is called hexadecimal number system. The constant hexadecimal values can be declared as,\u00a0const int hex = 0x40;<\/em> (It is the hexadecimal equivalent of the digit 64 in the decimal number system.)<\/li>\n<\/ol>\n

          4. Strings in C<\/h3>\n

          Just like characters, strings are used to store letters and digits.\u00a0Strings in C are referred to as an array of characters. It is enclosed within double quotes, unlike characters which are stored within single quotes.\u00a0<\/em>The termination of a string is represented by the null character that is \u2018\\0\u2019<\/strong>. The size of a string is the number of individual characters it has.<\/p>\n

          In C, a string can be declared in the following ways:<\/p>\n

          char name[30] = \u2018\u2019DataFlair\u201d; \/\/ The compiler reserves 30 bytes of memory<\/pre>\n
          char name[] = \u201cDataFlair\u201d; \/\/ The compiler reserves the required amount of memory<\/pre>\n
          char name[30] = { \u2018D\u2019 , \u2019a\u2019 , \u2019t\u2019 , \u2019a\u2019 , \u2019F\u2019 , \u2019l , \u2019a\u2019 , \u2019i\u2019 , \u2019r\u2019 , \u2019\\0\u2019 }; \/\/ How a string is represented as a set of characters.<\/pre>\n
          5. Special Symbols of C<\/h3>\n
          Apart from letters and digits, there are some special characters in C, which will help you to manipulate or perform data operations. Each special symbol has a specific meaning to the C compiler.<\/p>\n
            \n
          1. [ ]<\/strong> – Square brackets<\/em> –\u00a0<\/strong>The opening and closing brackets of an array indicate single and multidimensional subscripts.<\/li>\n
          2. ()<\/strong> – Simple brackets<\/em> <\/strong>– Used to represent function declaration and calls, used in print statements.<\/li>\n
          3. { }<\/strong> – Curly braces<\/em><\/strong> – Denote the start and end of a particular fragment of code which may be functions or loops or conditional statements.<\/li>\n
          4. ,<\/strong>\u00a0 –\u00a0\u00a0Comma <\/em><\/strong>– Separate more than one statements, like in the declaration of different variable names in C<\/a><\/strong>.<\/li>\n
          5. #<\/strong>\u00a0 – Hash \/ Pound \/ Preprocessor<\/em><\/strong> – A preprocessor directive, utilize for denoting the use of a header file.<\/li>\n
          6. *<\/strong>\u00a0 –\u00a0\u00a0Asterisk<\/em><\/strong>\u00a0 – To declare pointers, used as an operand for multiplication.<\/li>\n
          7. ~<\/strong> –\u00a0\u00a0Tilde<\/em><\/strong> – As a destructor to free memory.<\/li>\n
          8. .<\/strong>\u00a0 –\u00a0 Period\/dot <\/strong><\/em>– To access a member of a structure.<\/li>\n<\/ol>\n
            6. Operators in C<\/h3>\n
            Operators in C are tools or symbols, which are used to perform a specific operation on data. Operations are performed on operands.\u00a0Operators can be classified into three broad categories, according to the number of operands used. Which are as follows:<\/p>\n
            1. Unary<\/strong>:\u00a0 It involves the use of one a single operand.\u00a0For instance, \u2019!\u2019 is a unary operator which operates on a single variable, say \u2018c\u2019 as !c which denotes its negation or complement.<\/p>\n
            2. Binary<\/strong>:\u00a0 It involves the use of 2 operands. They are further classified as:<\/p>\n