Doubt in basic techniques

Hi to all, I am new to ARM world. Now i am trying with lpc2148. I have to write program for 4x4 keypad. So i thought to start with a single push button. i have written code for 16x2 LCD display. Now i am trying to type any char on keypad and display it on LCD. My LCD is working fine. I have written a code for single key. i ran that program and got no error. But when i debugging it the control does not enter in the coding. its stopped on SWI_Handler B SWI_Handler line.
Using my code i am trying to read
Here's my code

#include<lpc214x.h>
#include<stdio.h>

void delay(void);
//void keydetection(void);
unsigned int i,j,k;

int main()
{
IODIR0=0x00000000;//make all pins as input
PINSEL0=0x00000000;//make all pins as GPIO's
k=0x00000000;//make k as 32 bit variable

while(1)
{
IOSET0=0x00000001;//setting P0.0 pin as high
k=IOPIN0;//reading the states of P0.0 pin nd storn to k
printf("%d",k);
if(IOPIN0 && 0x00000001)//checkin P0.0 as high or not
IOSET0=0x00000011;//if its correct then P0.1 as high
delay();
IOCLR0=0x00000001;
k=IOPIN0;
printf("%d",k);
if(IOPIN0 && 0x00000000)
IOSET0=0x00000000;
delay();
}
}

void delay(void)
{
for(i=0;i<40000;i++)
{
;
}
}

Not only for this coding i am asking this doubt. My friends used to get this problem somany time. What this error exactly trying to say? What should i commenly do if i get this error? and whats the commen way to avoid this error?