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

int main()
{ 
	string s;
	char k; int i,c=0;

	cout<<"Enter String:";
	cin>>s;
	cout<<"Enter Character(a-z) : ";
	cin>>k;

	for(i=0;i<s.size();i++)     // size() return the size of the string   
	{ 
		if(s[i]==k)             /*here we check for each string element,if string element s[i] is 
		equalto character k then increase c by 1.*/
		c++;
	}
	cout<<k<<" occurs "<<c<<" times"<<endl;
	return 0;
}

Output

Enter String:IncludeHelp
Enter Character(a-z) : l
l occurs 2 times