LEN "Fred"+ LEN "Bloggs"	LEN ("Fred"+"Bloggs")
4+LEN "Bloggs"	LEN ("FredBloggs")
4+6	LEN "FredBloggs"
10	10

Functions can be separated in *built-in* (contained within *NextBASIC*) and *user-defined* ones (the ones we write). Below we'll visit the *in-built* functions categorised according to the datatype we give them as input to manipulate and/or transform. Please note that as the functions devoted to maths are a bit more complicated we will list them separately in their own chapter. ### String functions #### LEN **LEN** *x$*, works out the length of a string. Its single argument *x$* is the string whose length you want to find, and its result is the length, so that if you type ``` PRINT LEN "ZX Spectrum Next" ``` the answer **16** will be printed on screen, that is the number of characters in *ZX Spectrum Next* (spaces are counted as a character). #### STR$ **STR$** converts numbers into strings; that however is not its only capability and for that reason it has two forms. Apart from the simplest task of making a string out of a number in the way it would appear on screen displayed by a **PRINT** statement (that also means converted – or *cast* – into a decimal number), it can also do the same but converting at the same time the number to a different base! The simplest form **STR$** *x* doen't use parentheses to contain its single argument ***x*** –a number–, and its result is the string that would appear on the screen if the number were displayed by a **PRINT** statement. Note how its name ends in a **$** sign to show that its result is a string. For example, you could say: ``` a$=STR$ 1e2 ``` which would have exactly the same effect as typing: ``` a$="100" ``` since the numeric argument gets converted from scientific notation, to a standard decimal prior to printing. Or you could say: ``` PRINT LEN STR$ 100.000 ``` and get the answer **3**, because **STR$ 100.0000="100"**. **STR$(**_x_, [_base_ [, _places_]]**)** on the other hand uses parentheses, but takes up to 3 numeric arguments. It returns a string representation of number *n* in the optionally specified *base* (**2** to **36**). For bases > **10**, digits larger than **9** are represented with capital letters starting with **A**. If the base is not specified it's assumed it's **10**. If optional argument **places** is present, then a fractional part of places' digits is also output. Let's first rewrite the example above in a couple of ways: ``` a$=STR$ (1e2) a$=STR$ (1e2,16) ``` If you assumed prior to trying, that the first produces the same result as the **STR$** without parentheses further above, you'd be correct. It too, returns **100**. The second however demonstrates the power of conversion as we told **STR$** to convert to *base-16* (*hexadecimal*). This returns **64** which is **100** expressed in the hexadecimal system. The following two