What is the difference between a variable and a constant in computer programming?

Answer 1

a constant remains fixed with any kind if change in variation or the quantity whearas variables vary with certain quantities

a variable is al location in a memory which holds a piece of data ,it can be represented by anything apart from numbers.whearas

a constant can be any numbers or characters

if we talk in refernce with C Language:

• Variable is the named memory location whose value or you can say whose data can be change during execution of program. Where as Constant is the named memory location who value cann't be changed or whose value is fixed during the execution of the program.
• Variable's syntax is : data_type variable_name; and Constant's syntax is: const data_type constant_name=value;
• variable's example: int a; Constant's example is:const int a=28;
• Variables can be initialize after its declaration where as constants must be initialized at the time of there deceleration otherwise they will take a garbage/junk value.

Answer 2

Constants cannot change value and must be assigned a value at the point of instantiation (they must be defined).

Variables can change value at any time but do not need to be initialised at the point of instantiation. However, they must be initialised before they are read for the first time, so it's generally best to initialise as early as possible. Some languages, like C++, allow variables to be initialised at the same time they are instantiated. C, however, does not permit this; variables must be declared and initialised separately.

Constants are always allocated within the program's data segment. Static variables and global variables are also allocated in the data segment while local variables are allocated on the stack. You cannot have a named variable upon the heap (the free store). Heap memory can only be referred to (pointed at), it never be named.