A variable is an area in memory holding data and to which a name and data type have been assigned. In SAL you implicitly create a variable the first time you assign data to it. At that time you also implicitly assign a data type to that variable. Once a variable is assigned a type, that data type cannot be changed. This is to protect you from accidentally changing the type of a variable.
Space is allocated for all values between the beginning and ending dates.
SAL programs are compiled SAL programs are first compiled. This means that they are translated to a representation that is more compact and much faster to run. Because the SAL programs are first compiled you can get error messages during compilation or during execution. Compilation errors have to do with the syntax of your programs. Execution errors could be errors like dividing a number by a variable whose value is 0.