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Abhishek kushwaha
Abhishek kushwaha

Posted on • Updated on • Originally published at abbhishek.hashnode.dev

Variables in C - Programming Language

Variables

Variables are the name of a memory location where data is being stored .

int a = 10 ;
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Here we are storing the value 10 in a variable named a.

How to visulaise a variable in a place .

  • We can imagine a variable as a conatiner in any language where we can store some data and modify that in later down the line in code .

  • A variable make it easy for us to access the data we want to access for mathematical operations.

  • Lets take an example for better undersatnding :

    lets assume that i want to add some numbers in my c program and then print the result in terminal .

    
            int i = 10;
            int j = 20;
            // int k = i + j; 
    
            printf("%d \n", i + j);
    
    • When we run the code and its print the output we get our result , but here we are not able to store that data into something for later use .
    • So we need to store the result in a variable .

Rules for naming variables .

So there are bunch of rules and regulations for naming variables , that one should follow otherwise the compiler will give an error .

  • Variables must start with a letter or an underscore ("_").
  It means that if we start the variable name with a number then the compiler will give an error.

   we can make variable name as "_abc" or "abc_" or "abc"  

   but not "1abc" or "@abc" or "abc@" .

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  • Variables must not contain spaces or commas.
  It means that if we have a variable name which contains spaces then the compiler will give an error.

  we can make variable name as "abc1def" or "abc_def" or "abcdef"  

  but not "abc,def" or "abc def" or "abc@def" .

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  • Variables must not start with a number.
  It means that if we start the variable name with a number then the compiler will give an error.

  we can make variable name as "abc" or "abc_" or "abc"  

  but not "1abc" or "45abc" or "001_abc@" .

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  • Variables must not contain any special characters only "_" is allowed .
  It means that if we have a variable name which contains special characters then the compiler will give an error.

  we can make variable name as "abc" or "abc_" or "abc"  

  but not "1abc" or `@abc` or "abc@" .

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How to declare a variable .

  • We can declare a variable in two ways .
  • One is by using the keyword int .
  • Another is by using the keyword float .
  • we can also use the keyword char .
  • we can also use the keyword double .
  • All these keywords are used to declare a variable .

Lets take an example for better undersatnding :

    int i = 10;
    float f = 10.5;
    char c = 'a';
    double d = 10.5;

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  • Here we are declaring a variable named i and assigning it the value 10 .
  • Here we are declaring a variable named f and assigning it the value 10.5 .

  • Here we are declaring a variable named c and assigning it the value 'a' .

Here all these i , f , c , d are called variables .

  • Here all these int , float , char , double are called types of the variable and the type of data they can store , Datatypes.

we would be discussing datatypes in next Module !

How to assign a value to a variable .

  • We can assign a value to a variable by using the keyword = .
  • datatype variable_name = value_to_be_stores ;

Naming Convention

There are some convention for naming variables .
By following these convention we can make our code more readable and maintainable. Some of the convention are as follows:

  • Variable names should be written in lowercase_with_underscore.
  • Variable names should not start with a number.
  • Variable names should not contain any special characters.
  • Variable names should not contain spaces.
  • one should mantain a naming system for the variables so that with just one look we can find the variable, and predict here the value is comming from.

      int a = 10; 
    
      // here we are assigning the value 10 to the variable a , but with more code and more complexity we shall not be able to find the origin of a , and this can take a much time in debugging the code .
    
      int number = 10; 
    
      // here by just looking at the variable we can make a idea about the origin of the variable  number that its store some kind of number .
    
      int random_number = 10004546679667677;
    
      // here we can see that the variable `10004546679667677` is comming from the `random_number` variable.
    
      char user_name[20] = "Abhishek Kushwaha";
    
      // here we can see that the variable `Abhishek Kushwaha` is comming from the `user_name` variable.
    
      int user_age = 20;
    
      // here we can see that the variable `20` is comming from the `user_age` variable.
    
    

Top comments (4)

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pauljlucas profile image
Paul J. Lucas

You description of declaration isn't right. For example:

int a;
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is both a declaration and definition even though there's no assignment. Your example makes it looks like it's the assignment that makes it a definition which isn't true.

Your example of:

printf("%d", i + j);
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should be:

printf("%d\n", i + j);
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Variables should start with a letter or an underscore.

No. Variables must start with a letter or an underscore. "Should" makes it sound only recommended and not required. You have other uses of "should": they must all be "must."

Your example of:

int user_name = "Abhishek Kushwaha";
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is wrong. (You should be able to figure out why.)

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abbhiishek profile image
Abhishek kushwaha

Thanks for The review.
I appreciate your suggestions . 😊

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dhanashreerugi profile image
Dhanashree Rugi

int user_name = "Abhishek Kushwaha";

"Abhishek Kushwaha" is a character of array hence it has to be declared as,
char string_name[100] = "Abhishek Kushwaha";

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dhanashreerugi profile image
Dhanashree Rugi

correction please, its array of character not character of array.