Occurrences of each letter of alphabet in the text

Program to print a table indicating the no. of occurrences of each letter of alphabet in the text entered as command line arguments.

#include<iostream>
#include<string>
using namespace std;


int main(int argc, char *argv[])
{
string str="";
static int alphabet[26];
int x;


cout<<"\n\n Command-Line Argument\n";
for(int i=0;i<argc;i++)
{
cout<<"\n "<<argv[i];
str+=argv[i];
}


for(int i=0;i<str.length();i++)
{
if(str[i]>='A' && str[i]<='Z')
{
x=((int)str[i])-65;
alphabet[x]++;
}
else if(str[i]>='a' && str[i]<='z')
{
x=((int)str[i])-97;
alphabet[x]++;
}


}


//Displaying No. of occurrences of each alphabets in the command line argument
cout<<"\n\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n Alphabet No. of Occurrences\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~";
for(int i=0;i<26;i++)
{
cout<<"\n "<<(char)(65+i)<<" "<<alphabet[i];
}


system("pause");
return 0;
}