Downloading MinGW and setting Environment variable (path)

Steps followed

• Downloaded the MinGW file from this link http://sourceforge.net/projects/mingw/files/.

• After downloading, I installed the MinGW and selected only c and c++ option during my installation option, which downloaded some files from internet and showed the information in cmd prompt.

• MinGW is successfully installed in "C:\MinGW".

• Now the next step is to set the path variable in my Environment.
  
  
• My Computer - Right click - Properties - Advanced system settings.
  
  
• Environment variable - path 

• Select path and press edit.
  
  
• Add the MinGW bin path, so that the command line interpreter will know where to find them.

• Add - ";C:\MinGW\bin" .
  Make sure you add ";" at the beginning of the path.

Modulus operator using * and /

//  Program to implement modulus operator using * and /
#include <stdio.h>

int my_mod( int a, int b){
    return ( a - (b*(a/b)));
}

int main(){
    int a = 11;
    int b = 2;
    printf("Remainder = %d\n", my_mod(a,b));
    getch();
    return 0;
}

Reverse the digits using C

// Program to reverse the digits

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

int reverseDigit(int num){
    int reverseNum = 0;
    while(num > 0){
        reverseNum = (reverseNum << 3)+(reverseNum << 1)+num%10;
        num = num/10;
    }
    return reverseNum;
}

int reverseDigitForLoop(int num){
    int res;
    for(res = 0;num>0; res=(res*10)+num%10, num/=10);
    return res;
}

int main(){
    int num = 3456;
    printf("Reverse of %d is %d\n", num, reverseDigit(num));
    getch();
    return 0;
}

// Note: (reverseNum << 3) + (reverseNum <<1) == reverseNum * 10; 

STRCAT implementation in C

Method 1:

//Program to implement strcat

#include <stdio.h>

void my_strcat( char *dest, const char *src){
(*dest)? my_strcat(++dest, src):(*dest++ = *src++)?my_strcat(dest, src):0;
}

int main(){
    char dest[30] = "Umesh ";
    char *src = "Joga";
    my_strcat(dest, src);
    printf("Dest = %s\n", dest);
    getchar();
    return 0;
}

#if 0
Explanation:
1. my_strcat(dest, src) copies data of src to dest. 
2. To do so, it first reaches end of the string dest using recursive 
calls my_strcat(++dest, src). 
3. Once end of dest is reached, data is copied using (*dest++ = *src++)? 
 my_strcat(dest, src).
#endif


Method 2

#include <stdio.h>

char *my_strcat(char *dest, const char *src){
    int i, j;
    for(i = 0; dest[i] != '\0'; i++);
    //printf("Val of i = %d\n", i);
    for(j = 0; src[j] != '\0'; j++)
        dest[i+j] = src[j];
    //printf("Val of j = %d\n", j);
    dest[i+j] = '\0';
    return dest;
}

Method 3 
//Using pointer

char *mystrcat(char *dest, const char *src){
    while(*dest) dest++;
    while(*dest++ = *src++);
    return dest;
}

int main(){
    char *src = "Joga";
    char dest[20] = "Umesh ";
    printf("Dest = %s\n", my_strcat(dest, src));
    getchar();
    return 0;
}

SIZEOF implementation in C

// Program to implement sizeof operator

#include <stdio.h>
#define my_sizeof(type) (char *)(&type + 1)-(char *)(&type)

int main(){
    char x;
    printf("%d %d \n",(char *)(&x + 1), (char *)(&x));
    printf("%d", my_sizeof(x));
    getchar();
    return 0;
}

STRREV implementation in C

// Program to implement string reverse

#include <stdio.h>

void my_strrev( char *src ){
    int i, srcLen = 0;
    char temp;
    srcLen = strlen(src) - 1;
    for(i = 0; i < strlen(src)/2; i++){
        temp = src[i];
        src[i] = src[srcLen];
        src[srcLen--] = temp;
    }
}

int main(){
    char srcString[30] = "Umesh Joga";
    my_strrev(srcString);
    printf("Reversed sting = %s\n", srcString);
    getch();
    return 0;
}