Variable name not defined is a common error faced by programmers. It is very important to know about local and global variable declarations. In this blog, we learn the difference between local and global variables.
First thing we need to know here is the definition of scope of a variable. The scope of a variable is defined as the region in a program where a defined variable can have its existence and beyond the scope the variable cannot be accessed.
A global variable, as its name suggests , can be accessed anywhere. A local variable is a variable that can be accessed within its scope where it is defined .That is within the block of function where it is defined.
Let us see an example of local variables.
In this function called max , we use 2 variables a and b. a and b are both defined inside the function. So the scope of variables a and b is within the function max. Outside the function max, a and b do not exist. So a and b are local variables. Let us try accessing a outside the function max.
As we can see, when we tried to print a outside the function, there is an error saying a is not defined. This is because a is a local variable that can be operated on only within the function max.
A global variable as defined earlier can be accessed from any place in the program. Let us look at the following example. I am defining a variable c = 10. If a is greater than b , we return a+10 or else we return b+10. So here c is accessed from within the function max though it is not defined inside it.
Here c is a global variable. But we do not have to use “global” keyword here as we are only accessing c. Now if you want to modify c you need to specify it as global or else it will give an error.
Hope the concept of local and global variables is clear.