ACID properties of database

Atomicity

All changes to data are performed as if they are a single operation. That is, all the changes are performed, or none of them are.

For example, in an application that transfers funds from one account to another, the atomicity property ensures that, if a debit is made successfully from one account, the corresponding credit is made to the other account.

Consistency

Data is in a consistent state when a transaction starts and when it ends.

For example, in an application that transfers funds from one account to another, the consistency property ensures that the total value of funds in both the accounts is the same at the start and end of each transaction.

Isolation

The intermediate state of a transaction is invisible to other transactions. As a result, transactions that run concurrently appear to be serialized.

For example, in an application that transfers funds from one account to another, the isolation property ensures that another transaction sees the transferred funds in one account or the other, but not in both, nor in neither.

Durability

After a transaction successfully completes, changes to data persist and are not undone, even in the event of a system failure.

For example, in an application that transfers funds from one account to another, the durability property ensures that the changes made to each account will not be reversed.

DB2 vs MySql or Difference between DB2 and MySql

http://www.ibm.com/developerworks/data/library/techarticle/dm-0602tham2/#SQL comparisons

Program to find 2's complement

void revert(char *str,char *comp,int l);

int main()
{
  int i,found=0,l,stlen;
  char *str,*comp;

  clrscr();

printf("\nEnter a binary string\n");
gets(str);
stlen=strlen(str);
l=stlen;
l--;
       // printf("\nlength=%d..%c..",l,str[l]);
while(l)
{
if(found)
{
revert(str,comp,l);
break;
}
else
{
if(str[l]=='1')
found=1;
comp[l]=str[l];
printf("%c",str[l]);
l--;
}
}
printf("\ncopmlement is");
puts(comp);

getch();
return(0);
}


void revert(char *str,char *comp,int l)
{
while(l>=0)
{
if(str[l]=='1')
{printf("0");comp[l--]='0' ;}
else
{printf("1");comp[l--]='1';}
}
}

Program to Conver Hexadecimal String to Decimal number

int main()
{
char *str;
clrscr();
printf("\nEnter a hexadecimal string\n");
gets(str);

printf("\nthe corresponding decimal value is %d",htoi(str));
getch();
return(0);
}

int power (int a, int b) // utility function
{
int res = 1 ;
while( b>0 )
{
res *= a ;
b--;
}
return ( res );
}

int htoi ( char* s )
{
int result = 0,new_result;
//int value =0;
int len = strlen(s);
int exp = len;
char c;
int i;

  for( i=0; i<len; i++)
   {

    c = s[i];

     if ( c >='1' && c<='9')
new_result = (int)( (c - '0') * power(16, exp-1) );

     else
if (c >='A' && c<='F')
  new_result = (int)( (c - 55) * power(16, exp-1) );

    exp --;
    result += new_result;

   }

return (result);
}