Local Variable

Functions and procedures create new spaces within our code. Variables created within a function or procedure are called local variables. They live within the function or procedure, can only be accessed by the function or procedure’s code, and are removed from memory when the function or procedure ends.

Local variables:

• Is the term given to a variable that is declared within a function or procedure.
• Are limited in scope to the function or procedure where they are declared.
• Are good practice to use to store values. This makes it easy to understand how the variable is being used and where it is being changed.
• Have space allocated on the stack.
• Are removed from memory when their function or procedure ends.

Examples

The following code has local variables within each function. Each local variable lives within the function it is created inside, can only be accessed by that functions code, and is removed from memory when the function ends.

You may notice that both read_string and read_integer have variables called result - these are different variables. Remember that each function or procedure is isolated from the others, so the things they create only exist within their scope.

#include "splashkit.h"

using std::stoi;

/**
* Prompt the user to enter a string, and return the value to the caller.
*
* @param prompt The message to show the user
* @returns      The data entered by the user
*/
string read_string(string prompt)
{
    // Create a local variable called result
    string result;

    write(prompt);
    result = read_line();

    return result;
}

/**
* Prompt the user to enter an integer, and return the value to the caller.
*
* @param prompt The message to show the user
* @returns      The data entered by the user
*/
int read_integer(string prompt)
{
    // Create a local variable called line
    string line;
    line = read_string(prompt);
    while(! is_integer(line))
    {
        write_line("Please enter a whole number");
        line = read_string(prompt);
    }

    // Create a local variable called result
    int result;
    result = stoi(line);
    return result;
}

int main()
{
    write_line("Calling procedures is fun");

    // Create a local variable called name
    string name;
    name = read_string("Enter your name: ");

    // Create a local variable called number
    int number;
    number = read_integer("Enter your favourite number: ");
    //...
    return 0;
}