The Difference Between Variable Declaration and Definition

1. Variable Declaration

Variable declaration refers to informing the compiler about the type and name of a variable without allocating memory or initializing it. In Go, variable declaration is typically done using the var keyword.

1var x int

In this example, x is declared as a variable of type int, but at this point, x is not assigned any initial value. Go will allocate memory for x and initialize it to the zero value of the int type (i.e., 0).

2. Variable Definition

Variable definition refers to declaring a variable while simultaneously allocating memory and assigning it an initial value. In Go, variable definition can be done using the var keyword or the short variable declaration :=.

1var x int = 10 // x is declared as a variable of type int and initialized to 10
2x := 10       // x is declared and initialized to 10, and Go automatically infers the type of x as int

3. Summary of Differences

• Variable Declaration: Only declares the type and name of the variable without assigning an initial value. The variable is initialized to the zero value of its type.
• Variable Definition: Declares the type and name of the variable and assigns it an initial value. The variable is initialized to the specified value.