keywords and identifiers in c programming

keywords in C Programming

   There  are 32 keyword in c language.

     1.auto
     2.break
     3.case
     4.char
     5.const
     6. continue
     7. default
     8. double
     9. else
   10. enum
   11. extern
   12. float
   13. for
   14. goto
   15. if
   16. int
   17. long
   18. register
   19. return
   20. short
   21. signed
  22. sizeof
  23. static
  24. struct
  25. switch
  26. typedef
  27. union
  28. unsigned
  29. void
  30. volatile
  31. while
  32. do

details  of all Keywords in C

auto;

• The auto keyword declares automatic variables. For example:

            auto int var1;

• This statement suggests that var1 is a variable of storage class auto and type int.
• Variables declared within function bodies are automatic by default. They are recreated each time a function is executed.
•  automatic variables are local to a function, they are also called local variables. To learn more visit C storage class.

break and continue;

• The break statement makes program jump out of the innermost enclosing loop (while, do, for or switch statements) explicitly.
• The continue statement skips the certain statements inside the loop.
• for (i=1;i<=10;++i)

         {
             if (i==2)
          continue;
                if (i==5)
            break;
               printf("%d ",i);
              } v
            Output

             1 2 4

•     When i is equal to 2, continue statement comes into effect and skips 2. When i is equal to 5,    break statement comes into effect and terminates the for loop. To learn more, visit C break and continue statement

switch, case and default;

• The switch and case statement is used when a block of statements has to be executed among many blocks. For example:

             switch(expression)
        {
               case '1':
                   //some statements to execute when 1
                break;
               case '5':
               //some statements to execute when 5
               break;
               default:
                  //some statements to execute when default;
               }

char;

• The char keyword declares a character variable. For example char alphabet;
• Here, alphabet is a character type variable

const;

• An identifier can be declared constant by using const keyword.

• const int a = 5;

do...while;

• int i;

              do
             {
                   print("%d ",i);
                       i++;
              }
                    while (i<10)
             

double and float;

• Keywords double and float are used for declaring floating type variables. For example:float number;
• double longNumber;
• Here, number is single precision floating type variable whereas, longNumber is a double precision floating type variable.

if and else;

• In C programming, if and else are used to make decisions.

              if (i == 1)
                  printf("i is 1.")
             else
                prinf("i is not 1.")
                               If value of i is other than 1, output will be :

                            i is not 1

enum;

• Enumeration types are declared in C programming using keyword enum. For example:

               enum suit
                 {
                     hearts;
                     spades;
                     clubb;
                     banana;
                 };

• Here, a enumerated variable suit is created having tags: hearts, spades, clubs and banana.

extern;

• The extern keyword declares that a variable or a function has external linkage outside of the file it is declared
• for
• There are three types of loops in C programming. The for loop is written in C programming using keyword for. For example:

              for (i=0; i< 9;++i)
             {
               printf("%d ",i);
                }
                 Output

                     0 1 2 3 4 5 6 7 8

goto;

The goto keyword is used for unconditional jump to a labeled statement inside a function. For example:

       for(i=1; i<5; ++i)
      {
         if (i==10)
            goto error;
          }
                 printf("i is not 10");
          error:
         printf("Error, count cannot be 10.");
         Output

             Error, count cannot be 10.
       

int;

• The int keyword declares integer type variable. For example:int count;
•  count is a integer variable.
• short, long, signed and unsigned
• The short, long, signed and unsigned keywodrs are type modifiers that alters the meaning of a base data type to yield a new type.

• short int smallInteger;
• long int bigInteger;
• signed int normalInteger;
• unsigned int positiveInteger;
• Range of int type data types

Data types Range

• short int -32768 to 32767
• long int -2147483648 to 214743648
• signed int -32768 to 32767
• unsigned int 0 to 65535

return;

• The return keyword terminates the function and returns the value.

           int func()
         {
                 int b = 5;
                  return b;
         }

• This function func() returns 5 to the calling function. To learn more, visit C user-defined functions.

sizeof;

• The sizeof keyword evaluates the size of data (a variable or a constant).

              #include <stdio.h>
               int main()
                        {
                     printf("%u bytes.",sizeof(char));
                         }

              Output

            1 bytes.

register;

• The register keyword creates register variables which are much faster than normal variables.
• register int var1;

static;

• The static keyword creates static variable. The value of the static variables persists until the end of the program. For example:static int var;

struct;

• The struct keyword is used for declaring a structure. A structure can hold variables of different types under a single name.

            struct student{
                   char name[10];
                   float marks;
                        int age;
                   }s1, s2;

typedef;

• The typedef keyword is used to explicitly associate a type with an identifier.

           typedef float kg;
          kg bear, tiger;

union;

• A Union is used for grouping different types of variable under a single name.

          union student
        {
          char name[80];
           float marks;
           int age;
            }

void;

• The void keyword indicates that a function doesn't return any value.

          void testFunction(int a)
            {
             .....
               }

•  function testFunction( ) cannot return a value because the return type is void.

volatile;

• The volatile keyword is used for creating volatile objects. A volatile object can be modified in an unspecified way by the hardware.const volatile number number is a volatile object
•  number is a constant variable, the program cannot change it. However, hardware can change it since it is a volatile object.