aboutsummaryrefslogtreecommitdiffstats
path: root/source/arduino/string.rst
diff options
context:
space:
mode:
authorMarti Bolivar <mbolivar@mit.edu>2010-10-20 06:46:52 -0400
committerMarti Bolivar <mbolivar@mit.edu>2010-10-20 06:46:52 -0400
commit85c1c72db022bba891868afd3375e39dbe245701 (patch)
tree9d86a3db825667362a8c89a98a205586015aec94 /source/arduino/string.rst
parentabcfcc62cc62dfc088d30d5a6b6c36d6c89f7b07 (diff)
downloadlibrambutan-85c1c72db022bba891868afd3375e39dbe245701.tar.gz
librambutan-85c1c72db022bba891868afd3375e39dbe245701.zip
initial check-in of arduino docs in RST format (converted using wget+pandoc)
Diffstat (limited to 'source/arduino/string.rst')
-rw-r--r--source/arduino/string.rst158
1 files changed, 158 insertions, 0 deletions
diff --git a/source/arduino/string.rst b/source/arduino/string.rst
new file mode 100644
index 0000000..b841728
--- /dev/null
+++ b/source/arduino/string.rst
@@ -0,0 +1,158 @@
+.. _arduino-string:
+
+string
+======
+
+Description
+-----------
+
+Text strings can be represented in two ways. you can use the String
+data type, which is part of the core as of version 0019, or you can
+make a string out of an array of type char and null-terminate it.
+This page described the latter method. For more details on the
+String object, which gives you more functionality at the cost of
+more memory, see the
+`String object <http://arduino.cc/en/Reference/StringObject>`_
+page.
+
+
+
+Examples
+--------
+
+All of the following are valid declarations for strings.
+
+::
+
+ char Str1[15];
+ char Str2[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o'};
+ char Str3[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o', '\0'};
+ char Str4[ ] = "arduino";
+ char Str5[8] = "arduino";
+ char Str6[15] = "arduino";
+
+
+
+**Possibilities for declaring strings**
+
+
+
+
+- Declare an array of chars without initializing it as in Str1
+- Declare an array of chars (with one extra char) and the compiler
+ will add the required null character, as in Str2
+- Explicitly add the null character, Str3
+- Initialize with a string constant in quotation marks; the
+ compiler will size the array to fit the string constant and a
+ terminating null character, Str4
+- Initialize the array with an explicit size and string constant,
+ Str5
+- Initialize the array, leaving extra space for a larger string,
+ Str6
+
+
+
+**Null termination**
+
+
+
+Generally, strings are terminated with a null character (ASCII code
+0). This allows functions (like Serial.print()) to tell where the
+end of a string is. Otherwise, they would continue reading
+subsequent bytes of memory that aren't actually part of the
+string.
+
+
+
+This means that your string needs to have space for one more
+character than the text you want it to contain. That is why Str2
+and Str5 need to be eight characters, even though "arduino" is only
+seven - the last position is automatically filled with a null
+character. Str4 will be automatically sized to eight characters,
+one for the extra null. In Str3, we've explicitly included the null
+character (written '\\0') ourselves.
+
+
+
+Note that it's possible to have a string without a final null
+character (e.g. if you had specified the length of Str2 as seven
+instead of eight). This will break most functions that use strings,
+so you shouldn't do it intentionally. If you notice something
+behaving strangely (operating on characters not in the string),
+however, this could be the problem.
+
+
+
+**Single quotes or double quotes?**
+
+
+
+Strings are always defined inside double quotes ("Abc") and
+characters are always defined inside single quotes('A').
+
+
+
+**Wrapping long strings**
+
+
+
+You can wrap long strings like this:
+
+::
+
+ char myString[] = "This is the first line"
+ " this is the second line"
+ " etcetera";
+
+
+
+**Arrays of strings**
+
+
+
+It is often convenient, when working with large amounts of text,
+such as a project with an LCD display, to setup an array of
+strings. Because strings themselves are arrays, this is in actually
+an example of a two-dimensional array.
+
+
+
+In the code below, the asterisk after the datatype char "char\*"
+indicates that this is an array of "pointers". All array names are
+actually pointers, so this is required to make an array of arrays.
+Pointers are one of the more esoteric parts of C for beginners to
+understand, but it isn't necessary to understand pointers in detail
+to use them effectively here.
+
+
+
+Example
+-------
+
+::
+
+
+ char* myStrings[]={"This is string 1", "This is string 2", "This is string 3",
+ "This is string 4", "This is string 5","This is string 6"};
+
+ void setup(){
+ Serial.begin(9600);
+ }
+
+ void loop(){
+ for (int i = 0; i < 6; i++){
+ Serial.println(myStrings[i]);
+ delay(500);
+ }
+ }
+
+
+
+See Also
+--------
+
+
+- `array <http://arduino.cc/en/Reference/Array>`_
+- `PROGMEM <http://arduino.cc/en/Reference/PROGMEM>`_
+- `Variable Declaration <http://arduino.cc/en/Reference/VariableDeclaration>`_
+