aramonkg101's Feed - Programmer's Heaven

Re: Timed Input

Sun, 18 Jan 2009 04:55:17 -0700

Posted a 'reply on the C and C++ forum.

What device are we talking about? Do you have any documentation on the hardware(registers, memory, controller) or are you going to build it yourself? Connection? USB, serial, wireless? What Operating System are you going to work with? These are just a few questions to start with.

Re: linked stack problem with repeated output

Sat, 10 Jan 2009 09:51:56 -0700

Posted a 'reply on the Visual C++ forum.

Well, that you get no errors during compilation means that the syntax and grammar of the code violates no rules. It does not mean that the logic/design of the program is correct.

Also you have to decide in which language you are going to write the program in. Using malloc(), no classes but employing cin and cout is going to confuse you in the long run.

Finally not freeing up memory you use through malloc is bad practice and will only lead to problems.

The problem of repeated output is found somewhere here

      temp=(struct node *)malloc(sizeof(struct node));
      cout << "Enter a node data :";
      cin >> data;
      temp->data=data;
      temp->link=top;
      top=temp;

You always use struct node* top to save your values and you overwrite it. The problem is that with the structure of your program there is no easy way out of it. A corrected version of the code based on your approach is like this.

#include <stdio.h>
#include <stdlib.h>

struct node {    
  int data;
  struct node *link;
};

int main(int argc, char** argv){
  int choice, data;
  struct node base, *temp;

  base.link = NULL;

  /* Infinite loop is used to insert/delete infinite number of nodes */
  while(1) {
    printf("\n1.Push\n2.Pop\n3.Display\n4.Exit\n");
    printf("\nEnter ur choice:");        
    scanf("%d", &choice);
    
    switch(choice) {
    case 1:
      temp = &base;
      /* Find the last entry */
      while(temp->link != NULL)
	temp = temp->link;
      /* Allocate memory for the new entry */
      temp->link = (struct node *)malloc(sizeof(struct node));
      printf("Enter a node data :");
      scanf("%d", &data);
      /* The data is inserted in the new entry. NULL is set 
	 to show that this is the new last entry */
      temp->link->data = data;
      temp->link->link = NULL;
      break;   
    case 2:
      if(base.link == NULL){   
        printf("\nStack Underflow\n");
      }
      else{
	temp = &base;
	/* Finds the last entry but allows to free up memory too */
	while(temp->link->link != NULL)
	  temp = temp->link;
	printf("The poped element is %d", temp->link->data);
	free(temp->link);
	/* There is no data at temp->link anymore
	   so we set it to NULL */
	temp->link = NULL;
      }
      break;   
    case 3: 
      if(base.link == NULL){
        printf("\nStack is empty\n");
      }
      else{
	temp = base.link;
	/* Find and display all but last entry */
	while(temp->link != NULL) {
	  printf("->%d", temp->data); 
	  temp = temp->link;
	}
	printf("->%d", temp->data);
      }   
      break; 
    case 4:
      /* Free up memory used by malloc() calls */
      while(base.link != NULL){
	temp = &base;
	while(temp->link->link != NULL)
	  temp = temp->link;
	free(temp->link);
	temp->link = NULL;
      }
      exit(0);
    }           
  }  
  
  return 0;
}

To better design your stack take a look at this
http://www.cs.bu.edu/teaching/c/stack/linked-list/

If you want to use C++ consider classes.

Re: Timed Input

Sat, 10 Jan 2009 05:08:33 -0700

Posted a 'reply on the C and C++ forum.

Well, C++ does not provide the facilities you ask "out of the box". You could code it yourself if you had good knowledge of C++, perhaps some knowledge of assembly, some knowledge of operating system design and in-depth knowledge of the hardware of that device. Since you say you are a novice you probably do not have that.

So what you could do is use a library of classes/methods(C++) or functions(C) that will allow you to "communicate" with the device through a C++ program. Of course that is only possible if such a library exists and is available.

Alternatively you could use your own operating system's functionatily exposed to you through a set of functions found in your OS developer documentation. These set of functions, also called API, will provide you some control of the device but depending on the device what you can do may be limited.

Re: i have a doubt about malloc function

Thu, 08 Jan 2009 16:50:12 -0700

Posted a 'reply on the C and C++ forum.

You can access the byte at pointer+1 but the result of modifying it is undefined, which means that you may corrupt some other data structure, pointer or whatever else is at that address on the heap segment of memory.

What you can safely access and change is only the byte(s) malloc gives you.

Re: Pointer to Char Problem

Thu, 08 Jan 2009 15:52:54 -0700

Posted a 'reply on the C and C++ forum.

True that! Mae culpa. Which makes the code look something like this in the non-string class program.

 #include <iostream>
 using namespace std;
 
 int main()
 {
-  char *name = (char*) malloc(20);
+  char *name = (char*) new char[20];
   cout << " Enter your name with space(E.g Joe Mark)\n";
   cin.getline(name, 20);
   cout << name;
-  free(name);
+  delete [] name;
   system("pause");
   return 0;
}

Re: Print all possible combination of 4 digit numbers

Tue, 06 Jan 2009 13:50:05 -0700

Posted a 'reply on the C and C++ forum.

Well, not using language facilities will make your life only harder. Also if you want to change the number of digits that will be printed you will need to modify the code and add/remove nested loops.

To the point... You can use nested loops to find all the possible ways these four digits can be ordered (duplicate digits allowed) and then remove those in which a digit is found more than once. So that you get your permutations. It is a blunt solution, but it works. The code could be something like this for the case of 1,2,3 and 4.

#include <stdio.h>

int main(int argc, char** argv){
  int a,b,c,d;

  for(a=1; a<5; a++){
    for(b=1; b<5; b++){
      for(c=1; c<5; c++){
	for(d=1; d<5; d++){
	  if(!(a==b || a==c || a==d || b==c || b==d || c==d))
	    printf("%d%d%d%d\n",a,b,c,d);
	}
      }
    }
  }

  return 0;
}

Re: Compact Disc Writing in C programming

Tue, 06 Jan 2009 08:32:08 -0700

Posted a 'reply on the LINUX programming forum.

http://www.cdrkit.org/

Source code included :)

Re: mutex and threads

Tue, 06 Jan 2009 08:28:00 -0700

Posted a 'reply on the LINUX programming forum.

You could try this

https://computing.llnl.gov/tutorials/pthreads/

Re: C Multithreading/MultiTasking

Tue, 06 Jan 2009 08:19:36 -0700

Posted a 'reply on the C and C++ forum.

A detailed tutorial on POSIX Threads Programming for use with C language can be found here.

https://computing.llnl.gov/tutorials/pthreads/

Re: Pointer to Char Problem

Tue, 06 Jan 2009 08:11:17 -0700

Posted a 'reply on the C and C++ forum.

First you declare

char* Name;

while you use

cin.getline(name, 15);

Name and name are different, but I guess you have corrected it.
Also

cout << line;

Where do you declare line? I doubt this code compiled in that form...

So to correct your code in this form follow the suggestion of allocating memory for the pointer. For example...

char* name = (char*) malloc(SIZE_IN_BYTES_OF_MEMORY_REQUESTED);

Do not forget to free it up when done using it.

free(name);

Finally, since you use using C++ you are better off using C++ facilities, like the string class. So you could make these changes

 #include <iostream>
+#include <string>
 using namespace std;
 
 int main()
 {
-  char *name = (char*) malloc(20);
+  string name;
   cout << " Enter your name with space(E.g Joe Mark)\n";
-  cin.getline(name, 20);
+  getline(cin, name);
   cout << name;
-  free(name);
   system("pause");
   return 0;
 }

Re: virus scanner

Tue, 06 Jan 2009 06:24:51 -0700

Posted a 'reply on the Security forum.

If you want to take a look at source code for an antivirus product try

http://www.clamav.net/download/sources

The ClamAV product is licensed under GPL.

Re: Print all possible combination of 4 digit numbers

Tue, 06 Jan 2009 06:10:29 -0700

Posted a 'reply on the C and C++ forum.

Allow me a correction. What your program tries to do is find permutations not combinations.

The number of permutations of N objects by using R (R <= N) objects simultaneously is given by this formula...
P(N,R) = N! / (N - R)!

That said there are quite a few resources found online. For example

http://newton.ex.ac.uk/teaching/jmr/recursion.html

There you will find an elegant algorithm for finding permutations as well as a fine introduction to recursion, a very powerful technique in coding.