Variable names, duplicate

Duplicate variable names can cause all sorts of problems. You might use a variable called A to hold a value at the beginning of the program, and then inadvertently use the same variable name later on. If the program returns to the beginning, the value has changed. FOR-NEXT loops sometimes lead to duplication. When you re using a variable like A, make sure you don t use it as an index in a FOR-NEXT loop. And remember, only the first two characters of a variable count the computer thinks ALT is the same variable name as ALIEN. 

Testing variables can help you find a good number of bugs, especially when you have duplicated variable names (for example, using the name J in two different sections of a program). But remember, as soon as you press RETURN over a line, all variables will be lost. 

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