Interview Preparation Pointers - Revision history

Proj user14 at 19:07, 18 December 2016

2016-12-18T19:07:37Z

2016-12-18T18:44:29Z

2016-12-18T18:17:00Z

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2016-12-18T17:09:09Z

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2016-12-17T15:03:09Z

← Older revision		Revision as of 19:07, 18 December 2016
Line 166:		Line 166:

	The Max value is 200		The Max value is 200
		+	</pre>
		+
		+
		+	'''Array of Pointers'''
		+	There can be a situation where we have to maintain array , which stores pointers to int or char or any-other datatype. This can be done as follows.
		+
		+	<pre>
		+	Code :
		+
		+	#include <stdio.h>
		+
		+	int main () {
		+
		+	int var[] = {10, 100, 200};
		+	int i = 0, *ptr = var;
		+
		+	/* Print the values of array var */
		+	printf("Value of var[%d] = %d\n", i++, *(ptr++) );
		+	printf("Value of var[%d] = %d\n", i++, *(ptr++) );
		+	printf("Value of var[%d] = %d\n", i, *ptr );
		+	return 0;
		+	}
		+
		+	Output :
		+	Value of var[0] = 10
		+	Value of var[1] = 100
		+	Value of var[2] = 200
	</pre>		</pre>

@@ Line 48: / Line 48: @@
 </pre>
-'''Pointers to Pointer'''
+'''Pointer to Pointer'''
+   We have pointer to int, when we have  a pointer to pointer , our new pointer (n_ptr in this case) contains the address of the pointer (ptr in this case), which in turn points to the int variable.
 <pre>
 Code :

@@ Line 47: / Line 47: @@
 *p = 5;                        // Finally pointer points to location containing value 5
 </pre>
 '''Passing Pointers to a Function'''

@@ Line 85: / Line 85: @@
 '''Passing Pointer from a function'''
+   In the example below returning the address of the local variable outside a function is not a good idea , hence we declare the variable as static .
 <pre>
@@ Line 91: / Line 91: @@
 #include <stdio.h>
 /* function  return max number. */
 int* getMax( ) {

← Older revision		Revision as of 17:40, 18 December 2016
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	The value of num1 is 100 & num2 is 200		The value of num1 is 100 & num2 is 200
		+	</pre>
		+
		+
		+	'''Passing Pointer from a function'''
		+
		+
		+	<pre>
		+	Code:
		+	#include <stdio.h>
		+
		+
		+	/* function return max number. */
		+	int* getMax( ) {
		+
		+	static int a = 100;
		+	static int b = 200;
		+
		+	if (a > b)
		+	{
		+	return &a;
		+	}
		+	else
		+	{
		+	return &b;
		+	}
		+	}
		+
		+	/* main function to call above defined function */
		+	int main () {
		+
		+	/* a pointer to an int */
		+	int *p;
		+
		+	p = getMax();
		+	printf("The Max value is %d\n", *p);
		+
		+	return 0;
		+	}
		+
		+	Output :
		+
		+	The Max value is 200
	</pre>		</pre>

@@ Line 49: / Line 49: @@
 '''Passing Pointers to a Function'''
+   In the code below we have a defines a function values , which return void . It takes two parameters which are pointers to an integer. When the function is called the address of the integer is passed and not the value .
 <pre>
@@ Line 77: / Line 77: @@
+}
 </pre>

@@ Line 46: / Line 46: @@
 p = (int*)malloc(sizeof(int)); // Pointer equal to pointer type int that contain memory address space of int
 *p = 5;                        // Finally pointer points to location containing value 5
 </pre>

@@ Line 34: / Line 34: @@
 '''Malloc'''
     The Malloc function dynamically allocates memory when required. The function allocates size of byte of memory and returns a pointer to the first byte of NULL.
 <pre>
 Syntax:
 pointer = (type)malloc(size in bytes);