Program in C & C++ to count frequency of each letter in a string

Program in C & C++ to count frequency of each letter in a string

C PROGRAM

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
  void del(char *str,int *p)
   {
      int i;
       for(i=*p;i<strlen(str);i++)
       {
           if(str[i]==str[i+1]){
            *p=*p-1;
           }
           else
             str[i]=str[i+1];
       }
   }
   void frequency(const char *str1)
   {
     char letter[26],*str;
     int num[50],i,j,k;
     int len=strlen(str1);
     str=(char*)malloc(len+1);
     strcpy(str,str1);
     for(i=0;i<len;i++)
     {
         k=1;
         for(j=i+1;j<=len;j++)
         {
             if(tolower(str[i])==tolower(str[j]))
             {
                 k=k+1;
                 letter[i]=str[i];
                 num[i]=k;
                 del(str,&j);
             }
             else
             {
                 letter[i]=str[i];
                 num[i]=k;
             }
         }
     }
      printf("letter \t  Frequency\n");
     for(i=0;i<strlen(letter);i++)
         printf("%2c\t%6d\n",letter[i],num[i]);
   }
 int main()
  {
     frequency("Hello World");
     return 0;
  }

C++ PROGRAM

#include<iostream>
#include<conio.h>
#include<string.h>
#include<ctype.h>
 using namespace std;
  void del(char *str,int &p)
   {
       for(int i=p;i<strlen(str);i++)
       {
           if(str[i]==str[i+1]){
            p=p-1;
           }
           else
             str[i]=str[i+1];
       }
   }
   void frequency(const char *str1)
   {
     char letter[26],*str;
     int num[50],i,j,k;
     int len=strlen(str1);
     str=new char[len+1];
     strcpy(str,str1);
     for(i=0;i<len;i++)
     {
         k=1;
         for(j=i+1;j<=len;j++)
         {
             if(tolower(str[i])==tolower(str[j]))
             {
                 k=k+1;
                 letter[i]=str[i];
                 num[i]=k;
                 del(str,j);
             }
             else
             {
                 letter[i]=str[i];
                 num[i]=k;
             }
         }
     }
      cout<<" "<<"letter"<<"\t  "<<"Frequency"<<endl;
     for(i=0;i<strlen(letter);i++)
         cout<<"   "<<letter[i]<<"\t     "<<num[i]<<endl;
   }
 int main()
  {
     frequency("Programming.OM");
     return 0;
  }

Output :-

Program