From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/CONCEPT/arrays.html | 212 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 212 insertions(+) create mode 100644 reference/C/CONCEPT/arrays.html (limited to 'reference/C/CONCEPT/arrays.html') diff --git a/reference/C/CONCEPT/arrays.html b/reference/C/CONCEPT/arrays.html new file mode 100644 index 0000000..b56def1 --- /dev/null +++ b/reference/C/CONCEPT/arrays.html @@ -0,0 +1,212 @@ +Arrays + +
+
+

Arrays.

+
+
+Arrays can be created from any of the C data types +int, +float, +char. I start with int and +float +as these are the easiest to understand. Then move onto int +and float +multi dimentional arrays and finally char arrays + + + +
+

int and float arrays

+To define an integer or +floating point variable you would say. +
+	main()
+	{
+	  int   Count;		/* integer variable 		*/
+	  float Miles;		/* floating point variable	*/
+	}
+
+The syntax for an array is: +
+	main()
+	{
+	  int   Count[5];	/* 5 element integer array	*/
+	  float Miles[10];	/* 10 element floating point array */
+	}
+
+ +Now, the important fact is that the elements start at 0 (ZERO), so, +'Count' above has elements 0, 1, 2, 3, 4.

+To change the value of the 5th element we would code: +

+	main()
+	{
+	  int Count[5];
+	  Count[4] = 20;	/* code 4 to update the 5th element */
+	}
+
+ +If we want to initalise 'Count' at definition we can say: +
+	main()
+	{
+	  int i;
+	  int Count[5]={10, 20, 30};
+	  for (i=0; i< 5; i++)
+      	  {
+   	    printf("%d ", Count[i]);
+   	  }
+	  puts("");
+	}
+
+ +The result will be: +
+	10 20 30 0 0 
+
+We can see from the example above that the elements that have NOT been +initalised +have been set to zero.

+One last thing to show you. If all the elements are being +initialized when the variable is being defined, the compiler can work out +the number of elements for you. So this example will create an array +with 3 elements. +

+	main()
+	{
+	  int i;
+	  int Count[]={10, 20, 30};
+	}
+
+ +Don't forget, all the stuff so far also applies to float. +

+ + +

+

Two dimensional int and float arrays.

+ +C does not actually support multi-dimensional arrays, but you can +emulate them. +
+	main()
+	{
+	  int Count[5];
+	  int Matrix[10][4];
+	}
+
+Count has been seen before, it defines an array of 5 elements.

+Matrix is defined as 10 arrays, all with 4 elements.

+To initalise Matrix at definition, you would code the following. +

+	main()
+	{
+	  int Matrix[4][2]={{1, 2},
+	  		    {3, 4},
+			    {5, 6},
+			    {7, 8}};
+	}
+
+Dont forget the last element will be Matrix[3][1] +

+ + +

+

char arrays.

+ +char arrays work in the same way as int and float +
+	main()
+	{
+	  char Letter;
+	  char Letters[10];
+	}
+
+'Letter' can only hold one character but 'the 'Letters' array could hold 10. +It is important to think of 'char' as an array and NOT a string.

+To initalise 'char' variables you can use the following syntax. +

+	main()
+	{
+	  char Letter='x';
+	  char Letters[10]='f','a','x',' ','m','o','d','e','m','\0';
+	  char Text[10]="fax modem";
+	}
+
+Note that the double quotes mean 'text string' and so they will add the +NULL +automatically. This is the only time that text can be loaded into an array +in this way. If you want to change the contents of the array you should use +the function strcpy. +

+ + +

+

Two dimensional char arrays.

+ +Two dimensional arrays are a different kettle of fish! We can follow the +rules above to define the array like this. +
+	main()
+	{
+	  char Colours[3][6]={"red","green","blue"};
+
+	  printf ("%c \n", Colours[0][0]); 	/* O/P 'r' */
+	  printf ("%s \n", Colours[1]);    	/* O/P 'green' */
+	}
+
+ +The example above has reserved 18 consecutive bytes and created three +pointers into them. +
+
+                  ---------------------
+                 |red  \0green\0blue \0|
+                  ---------------------
+                  A      A      A
+                  |      |      |
+   Colours[0] ----       |      |
+   Colours[1] -----------       |
+   Colours[2] ------------------
+
+
+
+

+ +click here for chat on pointers. + +

+

+

+

+

+ + + + +
+Top + +Master Index + +Keywords + +Functions +
+
+

+ +

+
Martin Leslie + +
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