QBASIC TUTORIAL 4 - Variables

VARIABLES

This section discusses an important topic in programming, "variables." Please read this section thoroughly.

A variable is a piece of data kept in the computer's memory (RAM). The location of a variable in RAM is called the "address."

The following program prints the variable X to the screen:

     print X

Since the variable hasn't been assigned a number, the value of the variable is 0. So, the output of

the program is:

    0

This next program sets X to 15, and then prints the variable:

   X = 15

   print X

This time, the output is:

   15

In the above example, the number 15 was stored in the computer's RAM at a certain memory

address. Then the PRINT command accessed (or looked at) that address when it printed "15" to

the screen.

(NOTE: The memory address of X is not necessarily 1000000)

ADVANCED TIP: Although you don't normally need to, you can find the actual memory address of a variable (X, for example) by using the VARSEG and VARPTR commands.

   PRINT (VARSEG(X) * 65536) + VARPTR(X)

As in the programs above, a variable is accessed by calling its name. Variable names can have a

combination of letters and numbers. The following are valid variables:

   Y

   num

   VALUE

   xYz

   abc123

Also, you can use multiple variables in your program.

   X = 82

   Y = 101

   Z = 79

   PRINT X

   PRINT Y

   PRINT Z

Output:

   82

   101

   79

(NOTE: The memory addresses of these variables are not necessarily as specified)

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