C Programs

Concatenation of two strings in c programming language

#include<stdio.h>

int main(){

  int i=0,j=0;

  char str1[20],str2[20];

  puts("Enter first string");

  gets(str1);

  puts("Enter second string");

  gets(str2);

  printf("Before concatenation the strings are\n");

  puts(str1);

  puts(str2);

  while(str1[i]!='\0'){

      i++;

  }

  while(str2[j]!='\0'){

      str1[i++]=str2[j++];

  }

  str1[i]='\0';

  printf("After concatenation the strings are\n");

  puts(str1);

 return 0;

}

 

Program to change lowercase to uppercase and vice-versa:

#include<stdio.h>

#include<string.h>

int main(){

  char str[20];

  int i;

  printf("Enter any string:");

  gets(str);

  for(i=0;i<=strlen(str);i++){

            if(str[i]>=97&&str[i]<=122)

            str[i]=str[i]-32;

    else

    str[i]=str[i]+32;

}

    printf("Proper capitalisation is of great importance\n");   

    printf("%s\n",str);

  return 0;

}

OR

#include<stdio.h>

#include<string.h>

int main(){
   char str[20]="abcxyz";
  int i;

  for(i=0;str[i]!='\0';i++){
            if(str[i]>=97&&str[i]<=122)
            str[i]=str[i]-32;
    else
    str[i]=str[i]+32;
}
    cout<<"Proper capitalisation is of great importance\n";  
    cout<<str;
  return 0;
}

Program : Reverse String Without Using Library Function [ Strrev ]

#include<stdio.h>

#include<string.h>

void main()

{

 char str[100],temp;

 int i,j=0;

 printf("nEnter the string :");

 gets(str);

 i=0;

 j=strlen(str)-1;

 while(i<j)

     {

     temp=str[i];

     str[i]=str[j];

     str[j]=temp;

     i++;

     j--;

     }

 printf("nReverse string is :%s",str);

 return(0);

}