Convert character to lower and upper case in c++

Question

How can I compare character regardless of its case. Means suppose I enter Z if my if condition shall return true for both Z and z, character can be any alphabet from A-Z or a-z.
Like ABCbabcAABC
If I enter B then it I must get 4 as output because there are 4 B in string.
I am learning C++ on Turbo C++. I am trying to do but now not getting way out.

void main()
{
    clrscr();

    char str[50],ch;
    char str1[50];

    int i = 0, l;

    cout << "Enter strings: ";
    gets(str);
    cout << "Enter charcter: ";
    cin >> ch;

    l = strlen(str);

    for(i = 0; i <= l; i++)
    {
        cout << isupper(str[i]) ? tolower(str[i]) : toupper(str[i]);
    }

    puts(str);
    getch();
}

Answer 1

void main()
{
    clrscr();
    char str[50],ch;
    char str1[50];
    int i=0,l;
    cout<<"Enter strings: ";
    gets(str);
    cout<<"Enter charcter: ";
    cin>>ch;
    l=strlen(str);
    int result=0;
    for(i=0;i<l;i++)
    {
             if(tolower(ch)== tolower(str[i]))
        {
            result++;
        }
    }
puts(str);
puts(result);
getch();
}

Answer 2

if (tolower(str[i]) == tolower(ch)) {
    cout << (isupper(str[i]) ? tolower(str[i]) : toupper(str[i])); 
} else {
    cout << str[i];
}

40000 is the isupper output. Non zero for an upcase char, zero for lowercase, as written in manual

Answer 3

All you need to do is to play around with the ASCII value.

Check out the code: which explains that you need to convert only those characters whoce ASCII value is between 65(A) to 90(Z).

public class Ques2 {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) throws IOException {
    //ascii A=65 Z=90 a=97
    System.out.println("Enter UPPERCASE");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   // String input = br.readLine().toLowerCase();
    char c;
    char[] word=br.readLine().toCharArray();
   for(int i :word)
   {
       if(i>=65 && i<=90){
       i=i+32 ;
       c=(char) i;
        System.out.println(c);
       }
       else{
           c=(char)i;
           System.out.println(c);
       }
   }

}

}