Looking for a syntax

In a natural (human) language setting the syntax refers to all the rules that a speaker or writer has to respect to make the message understandable. They are the rules used to construct/build sentences.
Rules are numerous. Careful writer respect them, breaking sometimes some rules to produce a specific effect. Careless ones break the rules at will. Nevertheless, the message is more or less understandable because the reader often can readjust the ordering of the different parts of speech.

In a calculator, each function has its proper syntax. To get the intended (correct) result you must enter numbers and press keys in a specific order.

For example, if you want to calculate a+b you must enter number a, press the + sign, enter the second number (b) then press the equal sign to obtain the sum.
If you do not follow that particular key sequence you will not get the correct result.

That is the syntax of the addition operation on calculators that follow the direct algebraic syntax.

There are other calculators (notably the HP ones) thent use the so-called RPN (Reverse Polish Notation). In RPN, you perform an addition as follows
You type the first number and press ENTER
You type the second number
You type the [+] key to obtain the result.

As you can see the key sequence is different.

If you turn an RPN calculator ON and clear the stack (the holding area where operands are stored before being operated on) there is nothing in the stack.
Suppose you type 5, then press +. As soon as the operator (+) is pressed the calculator retrieves the last two numbers in the top of the stack. But finding only one number it complains about a syntax error . It cannot perform the operation because there is something missing.


In a natural (human) language setting the syntax refers to all the rules that a speaker or writer has to respect to make the message understandable. They are the rules used to construct/build sentences.
Rules are numerous. Careful writer respect them, breaking sometimes some rules to produce a specific effect. Careless ones break the rules at will. Nevertheless, the message is more or less understandable because the reader often can readjust the ordering of the different parts of speech.

In a calculator, each function has its proper syntax. To get the intended (correct) result you must enter numbers and press keys in a specific order.

For example, if you want to calculate a+b you must enter number a, press the + sign, enter the second number (b) then press the equal sign to obtain the sum.
If you do not follow that particular key sequence you will not get the correct result.

That is the syntax of the addition operation on calculators that follow the direct algebraic syntax.

There are other calculators (notably the HP ones) thent use the so-called RPN (Reverse Polish Notation). In RPN, you perform an addition as follows
You type the first number and press ENTER
You type the second number
You type the [+] key to obtain the result.

As you can see the key sequence is different.

If you turn an RPN calculator ON and clear the stack (the holding area where operands are stored before being operated on) there is nothing in the stack.
Suppose you type 5, then press +. As soon as the operator (+) is pressed the calculator retrieves the last two numbers in the top of the stack. But finding only one number it complains about a syntax error . It cannot perform the operation because there is something missing.