swap two variable in C

Q: Swap two variables in C?

1. Using Temporary Variable

#include <stdio.h>

int main(int argc, char *argv[]){
    int temp,num1,num2;
    printf("Enter Two Number: ");
    scanf(" %d %d", &num1, &num2);
    printf("Before Swap num1=%d and num2=%d\n", num1, num2);
    temp = num1;
    num1 = num2;
    num2 = temp;
    printf("After Swap num1=%d and num2=%d\n", num1, num2);
    return 0;
}

2. Not Using Temporary Variable

#include <stdio.h>

int main(int argc, char *argv[]){
    int num1,num2;
    printf("Enter Two Number: ");
    scanf(" %d %d", &num1, &num2);
    printf("Before Swap num1=%d and num2=%d\n", num1, num2);
    num1+=num2;
    num2 =num1-num2;
    num1 = num1-num2;
    printf("After Swap num1=%d and num2=%d\n", num1, num2);
    return 0;
}
/***********************************
* NOTE MEMORY OVER FLOW CAN HAPPEN *
***********************************/

3. Not Using Temporary Variable/Using Bitwise operator

#include <stdio.h>

int main(int argc, char *argv[]){
    int num1,num2;
    printf("Enter Two Number: ");
    scanf(" %d %d", &num1, &num2);
    printf("Before Swap num1=%d and num2=%d\n", num1, num2);
    num1^=num2;
    num2^=num1;
    num1^=num2;
    printf("After Swap num1=%d and num2=%d\n", num1, num2);
    return 0;
}

4. Using Bitwise operator and input From Command Line

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]){
    int num1; 
    int num2;
    if(argc != 3){
        printf("\nUSAGE:: %s <num1> <num2>\n",argv[0]);
        exit(-1);
    }
    num1 = atoi(argv[1]);
    num2 = atoi(argv[2]);
    printf("Before Swap num1=%d and num2=%d\n", num1, num2);
    num1^=num2;
    num2^=num1;
    num1^=num2;
    printf("After Swap num1=%d and num2=%d\n", num1, num2);
    return 0;
}

finding a number is even or odd using c

Q: Write a C program to Find whether a Number is Odd or Even?

Finding Odd or Even Using % operator.

#include<stdio.h>

int main(int argc, char * argv[]){
        int num=0;
        printf("\nInput a Number for Test:");
        scanf(" %d",&num);
        if(num%2 == 0){
                printf("%d IS EVEN\n",num);
        }
        else{
                printf("%d IS ODD\n", num);
        }
        return 0;
}

Compiling and Running Under Linux

rajesh@ubuntu:~/rajesh/c$ gcc iseven.c -o isev
rajesh@ubuntu:~/rajesh/c$ ./isev

Input a Number for Test:20
20 IS EVEN
rajesh@ubuntu:~/rajesh/c$ ./isev 

Input a Number for Test:11
11 IS ODD

Finding Odd or Even Using bit-wise operator.

#include<stdio.h>

int main(int argc, char * argv[]){
        int num=0;
        printf("\nInput a Number for Test:");
        scanf(" %d",&num);

        if(!(num&0x01)){
                printf("%d IS EVEN\n",num);
        }
        else{
                printf("%d IS ODD\n", num);
        }
        return 0;
}

Compiling and Running Under Linux

rajesh@ubuntu:~/rajesh/c$ gcc iseven1.c -o isev1
rajesh@ubuntu:~/rajesh/c$ ./isev1

Input a Number for Test:20
20 IS EVEN
rajesh@ubuntu:~/rajesh/c$ ./isev1 

Input a Number for Test:7
7 IS ODD

Finding Odd or Even Using bit-wise operator.Getting Input from Command Line.

#include<stdio.h>

int main(int argc, char * argv[]){
        int num=atoi(argv[1]);

        if(!(num&0x01)){
                printf("%d IS EVEN\n",num);
        }
        else{
                printf("%d IS ODD\n", num);
        }
        return 0;
}

Compiling and Running Under Linux

rajesh@ubuntu:~/rajesh/c$ gcc iseven2.c -o isev2
rajesh@ubuntu:~/rajesh/c$ ./isev2 12
12 IS EVEN
rajesh@ubuntu:~/rajesh/c$ ./isev2 13
13 IS ODD

Hello World For ARM

Hello World For ARM LPC2148

#include&ltLPC214x.h&gt
int main(){
    printf("Hello World!!!\n");
    return 0;
}

LPC2148

A Separate Page For LPC2148 Micro-Controller.

Executing shell commands using C

We Can Use system() function to execute a command

        #include <stdlib.h>
        int system(const char *command);

Small Example Code Snipet

int main(int argc, char *argv[]){
        const char *command = "ls";
        system(command);
        return 0;
}

system() executes a command specified in command by calling /bin/sh -c command, and returns after the command has been completed.
During execution of the command, SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.

A Complete Program.

QUESTION::
Write a C program to take set of commands separated by semicolons(;).
Execute each commands sequentially and wait till excution of commands over.

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

void executeCommand(const char *command)
{
        printf("\n=====================\n");
        system(command);
        printf("=====================\n");
}

int main(int argc, char *argv[]){
        char commands[1024];
        char *tempPos, *itrCommand;
        char command[256];
        int i;
        if(argc > 1)
        {
                memset(commands,0x00,sizeof(commands));
                for(i=1;i<argc;i++)
                {
                        strcat(commands,argv[i]);
                }
        }else{
                memset(commands,0x00,sizeof(commands));
                printf("Enter Commands Separated By Semicolon.\n");
                scanf(" %[^\n]s",commands);
        }
        printf("commands : %s\n",commands);
        itrCommand = commands;
        while(tempPos = strchr(itrCommand,';')){
                (*tempPos)=0x00;
                memset(command,0x00,sizeof(command));
                strcpy(command,itrCommand);
                executeCommand(command);
                itrCommand = tempPos+1;
                tempPos = NULL;
        }
        if((*itrCommand)!=0x00)
        {
                memset(command,0x00,sizeof(command));
                strcpy(command,itrCommand);
                executeCommand(command);
        }
        return 0;
}

Compilation and Excution In Linux System

rajesh@ubuntu:~/rajesh/Linux$ gcc system.c -o exe_using_C
rajesh@ubuntu:~/rajesh/Linux$ ./exe_using_C
Enter Commands Separated By Semicolon.
echo Rajesh;ls
commands : echo Rajesh;ls

=====================
Rajesh
=====================

=====================
a.out  executing.txt  exe_using_C  system.c
=====================
rajesh@ubuntu:~/rajesh/Linux$

Assembly Code To Blink LEDs

The Delay Generation ASM Routine For Generating Delay

;file: delays.asm
;ALL DELAYS ROUTINES HERE
DELAY_SEG SEGMENT CODE
RSEG DELAY_SEG
;DELAY OF 1MS SUBROUTINE
DELAY1MS:
MOV R7,#250
DJNZ R7,$
MOV R7,#247
DJNZ R7,$
RET
;DELAY OF 100MS SUBROUTINE
DELAY100MS:
MOV R6,#99;1MUS
L1:
ACALL DELAY1MS ;99MS
DJNZ R6,L1;198MUS
MOV R6,#250;1MUS
DJNZ R6,$;500US
MOV R6,#147;1US
DJNZ R6,$;294US
NOP
RET;1US
;DELAY 0F 1SEC SUB ROUTINE
DELAY1S:
MOV R5,#9
L2:
ACALL DELAY100MS
DJNZ R5,L2
MOV R5,#99
L3:
ACALL DELAY1MS
DJNZ R5,L3
MOV R5,#250
DJNZ R5,$
MOV R5,#138
DJNZ R5,$
RET

The Main ASM Routine For Operation

;file:main.asm
;Glow Alternate Leds Connected to A Port 0
$INCLUDE(delays.asm)
cseg at 0
MOV A,#0ffH
MOV A,#055H
MAIN:
MOV P2,A
LCALL DELAY1S
LCALL DELAY1S
XRL A,#0FFH
SJMP MAIN
END

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