:0Augusto, before C++ is C which handles text in byte or char arrays longer than the text will be. Always the way the text ends is with a character '\0' which = 0, also called NULL.
So you could have
char hello[ 16 ] = "Hello World";
hello[ 16 ] would be 16 chars == 'H' 'e' 'l' 'l' 'o' ' ' 'W' 'o' 'r' 'l' 'd' '\0' '\0' '\0' '\0' '\0' '\0'
'H' is also '\72'... here is an ASCII Table:
Once you understand that, spend time learning and getting used to C string functions. You might want to get a book (an old one, at deep discount) on just C language or look online for C tutorials and find the part(s) that deal with strings.
Please note that C strings are *not* C++ String Class Objects. Do not confuse string with String!
Here is the site where Arduino gets C++, link is to the libraries page:http://www.nongnu.org/avr-libc/user-manual/modules.html
Most C string functions and defines are in the string library. Some are automatic, others you must #include <string.h> to get:http://www.nongnu.org/avr-libc/user-manual/group__avr__string.html
strcpy() lets you copy strings. You can use it to load a string constant into an array.
char buffer[ 20 ]; // you can cut & paste these lines into a test sketch if you want
strcpy( buffer, "Hello" ); // but you will have to fill in the rest
Serial.println( buffer );
strcat() lets you add a string to a string.
strcat( buffer, " World" );
Serial.println( buffer );
There are too many for this post, for many uses.
I think of sprintf() as a string command though it is not, but it lets you format text and variables with fine control into a C string. You don't need to include a library but working out how to make the format string, you will want a guide! sprintf() is in stdio (standard in/out):http://www.nongnu.org/avr-libc/user-manual/group__avr__stdio.html
You might want to find a tutorial page depending on your current coding skills, here below is the section from the stdio.h page. Even if you do learn elsewhere, the short tight layout makes a good memory helper for later that fits on a page or screen.
Always keep references for quick check if you have the slightest doubt. To misspell a word or get things out of order means time spent bug hunting, it would be a shame to spend 1 hour finding out you should have spent 1 minute looking up syntax!
The format string is composed of zero or more directives: ordinary characters (not %), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments. Each conversion specification is introduced by the % character. The arguments must properly correspond (after type promotion) with the conversion specifier. After the %, the following appear in sequence:
Zero or more of the following flags:
# The value should be converted to an "alternate form". For c, d, i, s, and u conversions, this option has no effect. For o conversions, the precision of the number is increased to force the first character of the output string to a zero (except if a zero value is printed with an explicit precision of zero). For x and X conversions, a non-zero result has the string `0x' (or `0X' for X conversions) prepended to it.
0 (zero) Zero padding. For all conversions, the converted value is padded on the left with zeros rather than blanks. If a precision is given with a numeric conversion (d, i, o, u, i, x, and X), the 0 flag is ignored.
- A negative field width flag; the converted value is to be left adjusted on the field boundary. The converted value is padded on the right with blanks, rather than on the left with blanks or zeros. A - overrides a 0 if both are given.
' ' (space) A blank should be left before a positive number produced by a signed conversion (d, or i).
+ A sign must always be placed before a number produced by a signed conversion. A + overrides a space if both are used.
An optional decimal digit string specifying a minimum field width. If the converted value has fewer characters than the field width, it will be padded with spaces on the left (or right, if the left-adjustment flag has been given) to fill out the field width.
An optional precision, in the form of a period . followed by an optional digit string. If the digit string is omitted, the precision is taken as zero. This gives the minimum number of digits to appear for d, i, o, u, x, and X conversions, or the maximum number of characters to be printed from a string for s conversions.
An optional l or h length modifier, that specifies that the argument for the d, i, o, u, x, or X conversion is a "long int" rather than int. The h is ignored, as "short int" is equivalent to int.
A character that specifies the type of conversion to be applied.
The conversion specifiers and their meanings are:
diouxX The int (or appropriate variant) argument is converted to signed decimal (d and i), unsigned octal (o), unsigned decimal (u), or unsigned hexadecimal (x and X) notation. The letters "abcdef" are used for x conversions; the letters "ABCDEF" are used for X conversions. The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros.
p The void * argument is taken as an unsigned integer, and converted similarly as a %#x command would do.
c The int argument is converted to an "unsigned char", and the resulting character is written.
s The "char *" argument is expected to be a pointer to an array of character type (pointer to a string). Characters from the array are written up to (but not including) a terminating NUL character; if a precision is specified, no more than the number specified are written. If a precision is given, no null character need be present; if the precision is not specified, or is greater than the size of the array, the array must contain a terminating NUL character.
% A % is written. No argument is converted. The complete conversion specification is "%%".
eE The double argument is rounded and converted in the format "[-]d.dddeÂ±dd" where there is one digit before the decimal-point character and the number of digits after it is equal to the precision; if the precision is missing, it is taken as 6; if the precision is zero, no decimal-point character appears. An E conversion uses the letter 'E' (rather than 'e') to introduce the exponent. The exponent always contains two digits; if the value is zero, the exponent is 00.
fF The double argument is rounded and converted to decimal notation in the format "[-]ddd.ddd", where the number of digits after the decimal-point character is equal to the precision specification. If the precision is missing, it is taken as 6; if the precision is explicitly zero, no decimal-point character appears. If a decimal point appears, at least one digit appears before it.
gG The double argument is converted in style f or e (or F or E for G conversions). The precision specifies the number of significant digits. If the precision is missing, 6 digits are given; if the precision is zero, it is treated as 1. Style e is used if the exponent from its conversion is less than -4 or greater than or equal to the precision. Trailing zeros are removed from the fractional part of the result; a decimal point appears only if it is followed by at least one digit.
S Similar to the s format, except the pointer is expected to point to a program-memory (ROM) string instead of a RAM string.
In no case does a non-existent or small field width cause truncation of a numeric field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result.
This might be enough to get you started. Hey, I never said this would be a snap but it is something you should learn if you're going to write tight C code for small machines like UNO.
BTW, Good Luck and Good Future to You.