### Relational operators <, >, = ,<=, >=, <> | | | |---|---| | < | less than | | > | greater than | | = | equal to | | <= | less than or equal to | | >= | greater than or equal to | | <> | not equal to | Whereas you use them in their integer or floating point guise, the six relational operators, work very much in the same way. Like their floating point counterpart, they too produce a result of **0** for *false* and 1 for *true*. ### Expressions Expressions are useful because, whenever the computer is expecting a number from you, you can give it an expression instead and it will work out the answer. The exceptions to this rule are so few that they will be stated explicitly in every case. You can add together as many strings (or string variables) as you like in a single expression, and if you want, you can even use parentheses. In the case of Integer Expressions there are some further considerations and limitations as well as additional capabilities (ie. Bitwise operations and modulus) so they warrant a separate examination below. ### Variable names and limitations We really ought to tell you what you can and cannot use as the names of variables. As we have already said in *Chapter 1*, the name of a string variable has to be followed by **$**; otherwise they can be treated in the same way naming wise: They can use any letters or digits as long as the first one is a letter. You can put spaces in as well to make it easier to read, but they won't count as part of the name. Also, it doesn't make any difference to the name whether you type it in capitals or lowercase letters. There are some restrictions about variable names which are the same as commands (keywords), however, in general, if the variable contains a *NextBASIC* keyword in it (with spaces either side) then it won't be accepted. Integer variables are a bit different as they can only be a single letter **A** to **Z** (or lower case **a** to **z**) and they're assigned in an expression that begins with a **%** eg: ``` %a=10 ``` Additionally, all integer values are treated by default as unsigned 16-bit values except when you use the special **SGN {...}** keyword (in which case they're signed 16-bit – see the relevant section at the end of this chapter for details). All operations are performed within the confines of 16 bits, meaning all results are truncated to a max value of **65535**, with no checks for overflow/underflow (except division by zero, which results in error **6, Number too big**). Integer variables are pre-allocated and stored in a fixed location outside the normal memory used by *NextBASIC*. This gives a significant speed advantage as well as memory savings compared to the use of ordinary numeric variables. Further of note is that if a line contains an integer expression, *ALL* variables and arrays contained within the same expression are integer ones. In cases where there is more than one integer expression within a line, each needs to be preceded with a **%**. Here are some examples of the names of variables that are allowed: | | | |---|---| | **x** | | | **t42** | | | **ItIsWithAHeavyHeartThatIMustSay** | | | **nowWeAreSix** | |