Re: C programming Arrays
- From: "Marlon Brandão de Sousa" <splyt.lists@xxxxxxxxx>
- To: programmingblind@xxxxxxxxxxxxx
- Date: Tue, 9 Oct 2007 19:44:45 -0300
Hello,
Arrays may be seen as sequential variables, in the seense that they
are stored in contiguous spaces in memory. They allow an indexed
access and they have a specific syntax to do that.
See this and everything should be clearer now.
I have to declare 5 integers. I can do:
int a;
int b;
int c;
int d;
int e;
I can also have
int a, b, c, d, e;
All right, this is very good. Another option is this:
int intArray[4];
This declares an array called intArray (it could be called anything
you want) which contains space for five integers. To be clearer,
assuming an integer is 32 bits, this instruction will alocate 160 bits
of memory.
Arrays have the [] syntax which will let you access any one of the
array elements. Still in the given sample, the first element would be
accessed as intArray[0], the second element would be accessed as
intArray[1] ... and the fifth element would be accessed using
intArray[4] ...
And why arrays are usefull?
Because of many reazons, but let me show you just a good example of
this. I have five integers and I have to verify if all of them are
less than 100.
The code without array use follows:
#include <stdio.h>
int main()
{
// initializing the integers
int a=1, b=102, c=153, d=23, e=43;
if(a < 100 && b < 100 && c < 100 && d <100 && e= 100)
{
printf("All integers are less than one hundred\n";
}
else
{
printf("at least one of the integers are greater or equals to one hundred.\n";
}
return 0;
}
This code works greatly, but if you need to check one more integer you
would have to change most part of the code, declaring another variable
of type integer type and changing the if statement to include this new
integer in the check list.
Also, if you would put this in a function you would have to create a
function with 5 parameters, and pass all the integers to it. If you
wanted to put one more integer in the check list, you would have to
alter the function declaration, the function definition and still
declare one more integer in the main function and alter the function
call line to pass yet this new created integer to it.
If you didn't understand all this don't worry with it now, I just
wanted to show you that this solution, although useable, will generate
trouble if the code need to be changed. Now, see the same thing
achieved with use of array.
#include <stdio.h>
int main()
{
// instead of creating integers a through e we weill create an array
of integers which contains five integers
int intArray[4];
// Now, we will initialize all its members with some value
intArray = {1, 3, 133, 153, 4};
/*
Now, intArray[0], the first integer in the array, have the value 1.
IntArray[1], the second integer in the array, have the value 3.
And so on.
Now, we will check each one of the array integers against 100 and
we'll see if it is less than 100. First, we'll create an integer
variable which will act as our index. The index is the number between
the [ and ] and will tell the compiler what element of the array we're
interested in.
*/
int count; // index
/*
As our array starts at element 0 and finish at element 4 (thus five
integers) we will make a for loop which will start with count = 0 and
increment it untill it reaches the value 4, then exit
*/
for(count = 0; count <= 4; count++)
{
// now, we check if the element count of the array is less than 100
if(intArray[count] < 100)
{
printf("%d %s", intArray[count], " is less than 100!\n");
}
}
return 1;
}
Ok, if we wanted to add one more integer to the check list, it would
be a mather of changing int intArray[4] to int intArray[5] and include
another value in the initialization list. After this thee second
clause of the for statement should be changed to i <= 5 and it would
work.
If we wanted to use a function to do this operation, it wouldn't have
to be changed, cinse it would receive an array only, not five or six
integers.
Arrays may be dangerouse and are a little more complex than this in C,
but this is how it work. If you understand this let us know so we can
say you the trickier parts. If you still can't understand it please
ask again.
Marlon
2007/10/9, John Miller <n1umj@xxxxxxxxxxx>:
> Hi,
> Is there anyone that can give a good, actually reasonably understandable
> explanation or example of an array in C programming? In my class, the book's
> examples are horrible at best and confusing and the teacher should be fired
> his is so bad. That or I should drop the class which I was actually about to
> do but I looked and there is no other major completely online that holds my
> interest so I guess I have to stick it out for another torturous 5 weeks or
> what ever it is. I'm getting some of it, but not enough.
> Thanks,
> John Miller N1UMJ
> AIM and yahoo messenger: N1UMJ Skype: n1umjjohn
> home page:
> http://home.comcast.net/~n1umj/wsb/html/view.cgi-home.html-.html
> myspace: http://www.myspace.com/n1umj
>
> __________
> View the list's information and change your settings at
> //www.freelists.org/list/programmingblind
>
>
--
When you say "I wrote a program that crashed Windows," people just
stare at you blankly and say "Hey, I got those with the system, for
free."
Linus Torvalds
__________
View the list's information and change your settings at
//www.freelists.org/list/programmingblind
Other related posts:
