Can variable name start with numbers?

• Variable declaration tells the compiler about data type and size of the variable. Whereas, variable definition allocates memory to the variable
• Variable can be declared many times in a program. But, definition can happen only one time for a variable in a program.
• Variable declaration is for assignment of properties and identification to a variable. Whereas, variable definition is for assignments of storage space to a variable

• Local variable
• Global variable
• Environment variable

• The variables which are having scope/life only within the function are called local variables.
• These variables are declared within the function and can’t be accessed outside the function.

• The variables which are having scope/life throughout the program are called global variables.
• Global variable is defined outside the main function. So, this variable is visible to main function and all other sub-functions.

• Environment variable is a variable that will be available for all C applications and C programs.
• Once environment variables are exported, we can access them from anywhere in a C program without declaring and initializing in an application or C program.

• The symbols which are used to perform logical and mathematical operations in a C program are called C operators.
• These C operators join individual constants and variables to form expressions. Operators, functions, constants and variables are combined together to form expressions.

• The symbols which are used to perform logical and mathematical operations in a C program are called C operators.
• These C operators join individual constants and variables to form expressions. Operators, functions, constants and variables are combined together to form expressions.

Ternary operator is same as if else control statement in C.

Syntax : (Condition? true_value: false_value);

Example: (A > 100? 0: 1);

• C Arithmetic operators are used to perform mathematical calculations like addition, subtraction, multiplication, division and modulus in C programs.
• Arithmetic operators are +, -, *, /, %

• Assignment operators are used to assign the values to the variables.
• Assignment operators are =, +=, -=, /+, %= etc.