Basic Stamp 2






Programming Concepts & Tips


Microprocessors such as the one in the BS2 function with series of bits. Bits can have 2 values: 0 or 1, true or false, open or closed, etc. Fortunately we do not need to program with bits anymore. Over the years people have invented several languages that can be translated to binary strings. These languages share common characteristics. Below are the most important programming concepts.


Variables are containers for information. You can define a variable by giving it a name and a maximum size. Once a variable is defined, you can initialize it. That is to put information in it. In general the information is a number.
For example, you could define a variable called AccountNumber and say it can hold values less than 1 000. Then you could say that AccountNumber contains the value 345. This way everytime you refer to AccountNumber, you refer in fact to the number 345.


At any time you can put a new value in a variable. This is called an assignment operation.
For example, using the previous variabe AccountNumber, at any time in your program you could assign it a new value. You could say "now put 755 inside AccountNumber". This would erase the prevoius value of 345 and AccountNumber would now correspond to the number 755.


You can perform simple arithmetic operation on numbers and variables containing numbers. You can perform additions, substractions, multiplications, divisions, modulo, absolute value, etc.
For example, you could create the variable MyMoney that can hold a maximum of 10 000. Then say that MyMoney currently holds 5 000. You could then add numbers to MyMoney by using the addition and the assignment operators. You would say something like "take the value of MyMoney add it 600 and store the result back in MyMoney". MyMoney would then correspond to the number 5 600.


You can compare variables with each other.
For example, you could ask if MyMoney is greater than AccountNumber.


You can ask the program to perform a set of operations for a specific ammount of times. It is a very useful feature of most programming languages. This way you do not have to type the same commands over and over.
For example you could tell the program to flash a light on and off 50 times.

Control statements

This a powerful tool in programming. Control statements are of the form of " if this do that".
For example, you in a banking system, you could want to add a money bonus to your 10 first clients (account number from 001 to 010). You would do something like: if AccountNumber is smaller than 10 then add 25 to the money in that bank account.


A subroutine is a set of operations that has a name. You can refer to this name at anytime in your program. When you refer to a subroutine, the program jumps to this set of operations, performs them and goes back to the previous statement when it has finished.
For example, you could define a subroutine called FlashLights. You could insert statements in FlashLights such as: turn the lights on for 1 second, then turn the lights off. This way anywhere in your program, you could simply say "FlashLights". That would cause the program to perform the operations in the subroutine FlashLights and then go back to what it was doing before.


A comment is a string of information that will not be read by the microprocessor. In general, it is used to explain what a specific line of code means. You should use them as much as possible. This way when you read a program you wrote 2 months ago, you remember what each line of code was for.


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vincent leclerc . v@uttermatter.com . 11-19-2003
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i am not responsible for any problems caused by suggestions made in this workshop