Question:Conversion from uppercase to lower case using c program 

#include<stdio.h>
#include<string.h>
int main(){
  char str[20];
  int i;
  printf("Enter any string->");
  scanf("%s",str);
  printf("The string is->%s",str);
  for(i=0;i<=strlen(str);i++){
      if(str[i]>=65&&str[i]<=90)
       str[i]=str[i]+32;
  }
  printf("\nThe string in lower case is->%s",str);
  return 0;
}

Question:Write a c program to convert the string from lower case to upper case 

#include<stdio.h>
int main(){
  char str[20];
  int i;
  printf("Enter any string->");
  scanf("%s",str);
  printf("The string is->%s",str);
  for(i=0;i<=strlen(str);i++){
            if(str[i]>=97&&str[i]<=122)
            str[i]=str[i]-32;
  }
  printf("\nThe string in lowercase is->%s",str);
  return 0;
}

Question:COUNTING DIFFERENT CHARACTERS IN A STRING USING C PROGRAM 

#include <stdio.h>
int isvowel(char chk);
int main(){
  char text[1000], chk;
  int count;
  count = 0;
  while((text[count] = getchar()) != '\n')
            count++;
  text[count] = '\0';
  count = 0;
  while ((chk = text[count]) != '\0'){
      if (isvowel(chk)){
           if((chk = text[++count]) && isvowel(chk)){
               putchar(text[count -1]);
              putchar(text[count]);
              putchar('\n');
           }
      }
      else
           ++count;
  }
  return 0;
}
int isvowel(char chk){
  if(chk == 'a' || chk == 'e' || chk == 'i' || chk == 'o' || chk == 'u')
      return 1;
  return 0;
}

Question:Program for sorting of string in c language 

#include<stdio.h>
int main(){
  int i,j,n;
  char str[20][20],temp[20];
  puts("Enter the no. of string to be sorted");
  scanf("%d",&n);
  for(i=0;i<=n;i++)
      gets(str[i]);
  for(i=0;i<=n;i++)
      for(j=i+1;j<=n;j++){
           if(strcmp(str[i],str[j])>0){
               strcpy(temp,str[i]);
              strcpy(str[i],str[j]);
              strcpy(str[j],temp);
           }
      }
  printf("The sorted string\n");
  for(i=0;i<=n;i++)
      puts(str[i]);
  return 0;
}

Question: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;
}

Question:Concatenation of two strings using pointer in c programming language 

#include<stdio.h>
int main(){
  int i=0,j=0;
  char *str1,*str2,*str3;
  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){
      str3[i++]=*str1++;
  }
  while(*str2){
      str3[i++]=*str2++;
  }
  str3[i]='\0';
  printf("After concatenation the strings are\n");
  puts(str3);
  return 0;
}

Question:C code which prints initial of any name 

#include<stdio.h>
int main(){
   char str[20];
   int i=0;
   printf("Enter a string: ");
   gets(str);
   printf("%c",*str);
   while(str[i]!='\0'){
       if(str[i]==' '){
            i++;
            printf("%c",*(str+i));
       }
       i++;
   }
   return 0;
}
Sample output:
Enter a string: Robert De Niro
RDN

Question:Write a c program to print the string from given character 

#include<string.h>
#include<stdio.h>
int main(){
  char *p;
  char s[20],s1[1];
  printf("\nEnter a string: ");
  scanf("%[^\n]",s);
  fflush(stdin);
  printf("\nEnter character: ");
  gets(s1);
  p=strpbrk(s,s1);
  printf("\nThe string from the given character is: %s",p);
  return 0;
}

Question:String reverse using strrev in c programming language 

#include<stdio.h>
#include<string.h>
int main(){
    char str[50];
    char *rev;
    printf("Enter any string : ");
    scanf("%s",str);
    rev = strrev(str);
   
    printf("Reverse string is : %s",rev);
   
    return 0;
}

Question:How to reverse a string in c without using reverse function 

#include<stdio.h>
int main(){
    char str[50];
    char rev[50];
    int i=-1,j=0;

    printf("Enter any string : ");
    scanf("%s",str);
   
    while(str[++i]!='\0');

    while(i>=0)
     rev[j++] = str[--i];

    rev[j]='\0';
  
    printf("Reverse of string is : %s",rev);
  
    return 0;
}
Sample output:
Enter any string : cquestionbank.blogspot.com
Reverse of string is : moc.topsgolb.knabnoitseuqc