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Basic IO's

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Control Statements

What is Control Statement C if Statement C if else Statement C Nested if Statement C Else if Statement C Break Statement C Continue Statement C Switch Statement C Goto Statement

Looping

What is Control Loop C for Loop C Nested for Loop C while Loop C Nested while Loop C do while Loop C Nested do while loop

Functions

What is Function C User Defined Functions C Recursion C Passing Parameters

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What is Storage Class C Auto C Extern C Static C Register

Array

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String

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Pointer

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What is Structure C Struct within Struct C Array within Structure C Pointer to Structure C Structure and Function C Enum C Bitfield Structure C Type def

Union

What is Union

Files

What is File C read a file C write a file C File Handling C Error Handling C Low Level Disk I/O C Other file functions

Memory Allocation

What is Memory Allocation C Malloc() C Calloc() C Free() C Realloc() C Coreleft()

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The ones who are crazy enough to think they can change the world are the ones who do.
- Steve Jobs

C Realloc()

Why Realloc()

Now, you are already partition the microprocessor's memory to your 6 team either by using malloc() or by using calloc(). One of your team demand for extra memory space as they are left with zero space of their allocated memory, now it's your responsibility to allocated memory to that team so that they can complete their task. Here is the function to reallocate the memory space to whomsoever are in demand of memory.

Realloc in calloc

realloc in calloc in c

Realloc in malloc

realloc in malloc c

What is Realloc?

  • realloc() is the programmer's shorthand to represent reallocation.
  • realloc() reallocates the already allocated memory.
  • realloc() allocates an exact quantity of memory explicitly to a program, when required.
  • allocation of memory is done either in consecutive memory location or in non-consecutive memory location.

Realloc() Syntax

Syntax
data_type *realloc  (no of spaces, size of data_type);

C Program - Realloc()

Let us consider that our user will enter 3 numbers and we allocated three spaces for interger number using malloc() inbuilt memory function and then if our user enter more than three numbers, we should not stop our user instead we need to reallocate the number to the same pointer variable using realloc().

realloc.c
#include <stdio.h>
#include <stdlib.h>
int main()
{
int *numbers = (int*)malloc(3* sizeof(int));
int i, space = 3, number, n = 0;
printf("malloc allocated 3 memory spaces\n\n");
printf("Enter as many numbers you like or -1 to exit\n");
scanf("%d ",&number);
while(number !=-1)
{
if(n >= space)
{
space+=3;
printf("reallocate 3 more memory\n");
numbers = (int*)realloc(numbers, space * sizeof(int));
}
numbers[n] = number;
if(n!=0)
scanf("%d",&number);
n++;
}
printf("The numbers you entered...\n");
for(i = 0;i < n;i++)
printf("%3d", numbers[i]);
return 0;
}
  • malloc allocated 3 memory spaces
  • Enter as many numbers you like or -1 to exit
  • 1
  • 2
  • 3
  • reallocate 3 more memory..
  • 4
  • 5
  • 6
  • reallocate 3 more memory
  • -1
  • The numbers you entered...
  • 1 2 3 4 5 6

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