StartingC - Revision history

GethinWilliams at 14:43, 4 October 2013

2013-10-04T14:43:07Z

2013-10-04T14:36:50Z

Pointers and Allocatable Memory

2013-10-04T10:20:28Z

Types & Operations

2011-03-07T16:31:10Z

Going Further

2010-07-05T15:58:48Z

2010-02-11T15:22:28Z

Conditionals & Loops

2010-02-10T16:35:32Z

Pointers and Allocatable Memory

2009-10-08T16:35:15Z

Conditionals & Loops

2009-10-08T16:34:55Z

Conditionals & Loops

2009-10-08T16:30:11Z

Types & Operations

@@ Line 487: / Line 487: @@
 You'll recall that arrays are chucks of contiguous memory referenced through the address of the first element.  If we declare a pointer to the variable type we're interested in and then invoke a command to pair it with a chuck of memory, we'll be in business, right?  Enter the '''malloc''' function:
-<pre>
+<source lang="c">
    iAddr = (int *)malloc(sizeof(int)*MAXCOUNT);
-</pre>
+  /* After requesting space it is good practice to check
 On one line, we've rather neatly requested a chunk of contiguous memory with malloc.  We've requested the number of bytes required to store an integer, multiplied the number of elements we desire in our new array.  The malloc function returns a general purpose '''pointer to void (void *)''', which we've quickly cast to be a pointer to an integer so that the RHS matches the LHS in our assignment to trusty old iAddr.  Bingo, we have our new array; arranged on-the-fly, primed and ready to go!

@@ Line 158: / Line 158: @@
 types.c
-* declare a character array sufficient to record the state of a game of naughts and crosses, populate is and print it to the screen.
+* declare a character array sufficient to record the state of a game of naughts and crosses, populate it and print it to the screen.
 * How many bytes is used to store a long double?
 * You can give an initial value to a character array when you declare it (e.g. char cStr[20] = "xxxxxxxxxxxxxxxxxxxx";).  What happens if we leave '\0' out of character assignments in this case?

← Older revision		Revision as of 16:31, 7 March 2011
Line 701:		Line 701:
	'''Further Reading'''		'''Further Reading'''

−	* The bible is ~~[http://en.wikipedia.org/wiki/The_C_Programming_Language_(book)~~ The C Programming Language] by Kernighan & Ritchie. I'~~ve never used anything else.~~	+	* The bible is '''The C Programming Language''' by Kernighan & Ritchie--often shortened to just '''K&R'''. Take a look at the [[A_Good_Read\|'A Good Read?']] page for more details.
−	* [http://oreilly.com/pub/topic/cprog O'~~Reilly~~] ~~rarely produce a dud~~.

@@ Line 7: / Line 7: @@
 <pre>
-svn co http://source.ggy.bris.ac.uk/subversion-open/startingC/trunk ./startingC
+svn co https://svn.ggy.bris.ac.uk/subversion-open/startingC/trunk ./startingC
 </pre>

@@ Line 180: / Line 180: @@
 <pre>
    if ( temperature < 0.0 ) {
-     printf("Water would normally freeze at:\t%f\tdegrees C\n");
+     printf("Water would normally freeze at:\t%f\tdegrees C\n", temperature);
+   }
    else if (temperature > 100.0 ) {
-     printf("Water would normally boil at:\t%f\tdegrees C\n");
+     printf("Water would normally boil at:\t%f\tdegrees C\n", temperature);
+   }
    else {

@@ Line 437: / Line 437: @@
 make
 </pre>
 Looking inside '''pointers.c''', we don't have to wait long to see something new.  In the variable declaration block we see:

@@ Line 207: / Line 207: @@
 </pre>
-The '''default''' case is much like our '''else''' catch-all in the box above and is important to include as otherwise you will be vulnerable to a 'fall-through' bug.  This is when none of the cases trigger because we did not consider the actual value passed to switch().  You will also notice the '''break''' statements in all the cases.  Adding these is also a defensive maneouvre, since we could accidentally trigger two cases.  Case 4 and the default, say.  A '''caveat''', however, is that the expression in the parentheses of '''switch(expr)''', must be integer valued.
+The '''default''' case is much like our '''else''' catch-all in the box above and is important to include as otherwise you will be vulnerable to a 'fall-through' bug.  This is when none of the cases trigger because we did not consider the actual value passed to switch().  You will also notice the '''break''' statements in all the cases.  Adding these is also a defensive maneouvre, since we could accidentally trigger two cases.  Case 4 and the default, say.  A '''caveat''', however, is that the expression in the parentheses of '''switch(expr)''', must be '''integer''' valued.
 ----

@@ Line 49: / Line 49: @@
 </pre>
-Take a look inside '''types.c''' and after the start of the main function, you'll see a block of '''variable declarations''':
+Take a look inside '''types.c''' (it's best to run your text editor in the background, so that you can type make etc. when needed) and after the start of the main function, you'll see a block of '''variable declarations''':
 <pre>