Constants and variables in c programming

The following Slide explains about the conventions and rules of Constants and Variables in C programming.

1. Constants and Variables in C programming Chitrank Dixit

2. Constants Any unchanged value in a program during the program execution is called constant. Following are the constants in C language. Numeric Constants String or Character Constants.

3. Numeric Constants Integer Constant An integer constant is a signed or unsigned whole number . Example:          - 23       + 356         46 C language supports an integer constant in octal (base 8) , decimal (base 10) and hexadecimal (base 16). The default number system followed in C language is decimal (base 10 ). An octal number is preceded by zero ( ) and a hexadecimal number is preceded by  0x  or  0X .

4. Real or floating point constant :   Any signed or unsigned number with fractional part is called real or floating point constant. A real constant can be written in decimal or exponential form . Example Decimal Form                  0.254         +342.0          -3.15 Exponential Form            0.218e6      0.42e-32       -1.0e12 ( 0.218e6 means --> 0.218 x 10^6 and so on for all )

5. String or Character Constants Any string of characters enclosed in apostrophes or quotes is called string constant or character constant. There are two types of string constants . Single Character String Constant String of Characters Constant

6. Single Character String Constant Any letter or character enclosed in single apostrophe is called single character string constant. Example:              'y'      '$'       '+'

7. String of Characters Constant Any string of characters consisting of letters, digits and symbols enclosed in double quotes is called string of characters constant . Example : "Total value is“ , “12 vyas fala ”, “value is = “

8. Variables A variable is an identifier or a name which is used to refer a value and this value varies or changes during the program execution. A variable is written with a combination of letters , numbers and special characters _(underscore) with the first letter being an alphabet. Maximum of 31 letters can be used to write a variable . Example:  x , fact , c22 , total_value  

9. Important rules while writing a variable in C Programming Upper and Lower case alphabets are taken differently, so the variables  SUM  and  sum  are referring to different values. No special characters other than underscore ( _ ) are permitted . Some C compilers will not accept more than 8 characters. So it is a good practice writing a variable with few letters which makes it also convenient to write and use All variables used in a C program are declared with appropriate data types before the variable is assigned any value . Reserved words cannot be used as variables.