the entered character is a lowercase, uppercase, or a real number

Hi

I'm trying to write a simple programme to find if the entered character is a lowercase, uppercase, or a real number. Please don't forget I'm a beginner and know very little. So, please explain in as much detail as possible. I have a rough draft. I know there are two or more ways to do this but someone wants me to do this 'terrible' way. So, please help me. I can understand the look of the code might frustrate you. It did me. I'm sorry for that.

Code:

#include <iostream>
#include <conio.h>

int main()

{
	char r;
	cout << "Enter the letter" << endl;
	cin >> r;
	if ( (r=='A')||(r=='B')||(r=='C')||(r='D')||(r=='E')||(r=='F')||(r=='G')||(r=='H')||          
        (r=='I')||(r=='J')||(r=='K')||(r=='L')||(r=='M')||(r=='N')||(r=='O')||(r=='P')||(r=='Q')||    
        (r=='R')||(r=='S')||(r=='T')||(r=='U')||(r=='V')||(r=='W')||(r=='X')||(r=='Y')||(r=='Z') )
	cout << "r is uppercase" << endl;
	
        else
	if ( (r=='a')||(r=='b')||(r=='c')||(r='d')||(r=='e')||(r=='f')||(r=='g')||(r=='h')||(r=='i')|| 
        (r=='j')||(r=='k')||(r=='l')||(r=='m')||(r=='n')||(r=='o')||(r=='p')||(r=='q')||(r=='r')||
        (r=='s')||(r=='t')||(r=='u')||(r=='v')||(r=='w')||(r=='x')||(r=='y')||(r=='z') )
	cout << "r is lowercase" << endl;
	
        else
	if (r is a real number)
	else
	???
	getch();
}

As I said in the other thread, you shouldn't use conio.h, you should replace getch() with cin.get(), add return 0; to the end of main() and fix your indentation.

Now, what stands out to me here is that you can use <, <=, >, >= on char values to test ranges just like with numbers, but it appears you don't know this. It means you can replace:

Code:

if ( (r=='A')||(r=='B')||(r=='C')||(r='D')||(r=='E')||(r=='F')||(r=='G')||(r=='H')||          
        (r=='I')||(r=='J')||(r=='K')||(r=='L')||(r=='M')||(r=='N')||(r=='O')||(r=='P')||(r=='Q')||    
        (r=='R')||(r=='S')||(r=='T')||(r=='U')||(r=='V')||(r=='W')||(r=='X')||(r=='Y')||(r=='Z') )

with

Code:

if ('A' <= r && r <= 'Z')

Also, where you have "???", don't you want to print an error message about invalid input?

Thanks a lot, Mozza314.

It is an incomplete code. The problem is the person who is instructing is actually 'forcing' me to use his old ways. What can I do then? I have been told my codes contain many things which are now outdated. Next week I'm going to argue with that person.

I will come to your simple and neat method later. First I want to do it this way in all its nastiness.

At the top I declare "r" a character. Isn't it wrong? Because I'm trying to write a programme which tell if "r" is lowercase, uppercase, or a real number. Can a "char" be a real number?

Bold part is incomplete. I need your help there.

One thing more, let's say, when I write the blue line in Dev-C++ it never ends. I have to scroll left and right to see the line. Isn't there some way that I could wrap this lengthy line into sections as they appear here? Do you get what I'm saying?

Please now help me.

Code:

#include <iostream>
#include <conio.h>

int main()

{
	char r;
	cout << "Enter the letter" << endl;
	cin >> r;
	if ( (r=='A')||(r=='B')||(r=='C')||(r='D')||(r=='E')||(r=='F')||(r=='G')||(r=='H')||          
        (r=='I')||(r=='J')||(r=='K')||(r=='L')||(r=='M')||(r=='N')||(r=='O')||(r=='P')||(r=='Q')||    
        (r=='R')||(r=='S')||(r=='T')||(r=='U')||(r=='V')||(r=='W')||(r=='X')||(r=='Y')||(r=='Z') )
	        cout << "r is uppercase" << endl;
	
        else if ( (r=='a')||(r=='b')||(r=='c')||(r='d')||(r=='e')||(r=='f')||(r=='g')||(r=='h')||  
        (r=='i')||(r=='j')||(r=='k')||(r=='l')||(r=='m')||(r=='n')||(r=='o')||(r=='p')||(r=='q')|| 
        (r=='r')||(r=='s')||(r=='t')||(r=='u')||(r=='v')||(r=='w')||(r=='x')||(r=='y')||(r=='z') )
	        cout << "r is lowercase" << endl;
	
        else
	if (r is a real number)
	else
	???
	getch();
}

A char is actually a small numeric type. You may want to take a look at this link Variables go to the section titled "Fundamental data types". Also this link about the ASCII Characters will show the numeric values for the alphabet.

Jim

Originally Posted by jackson6612

Can a "char" be a real number?

Not really. And "real number" is the wrong term even if you're talking about something stored in a double. You'd need infinite precision to store real numbers. The correct term for these values in computer science is "floating point value".

Anyway, there's two ways I see to do this within the limits of where you're programming knowledge is - either use peek() or figure out how to convert a string into a floating point value.

Originally Posted by jackson6612

Thanks a lot, Mozza314.

It is an incomplete code. The problem is the person who is instructing is actually 'forcing' me to use his old ways. What can I do then? I have been told my codes contain many things which are now outdated. Next week I'm going to argue with that person.

I will come to your simple and neat method later. First I want to do it this way in all its nastiness.

At the top I declare "r" a character. Isn't it wrong? Because I'm trying to write a programme which tell if "r" is lowercase, uppercase, or a real number. Can a "char" be a real number?

Bold part is incomplete. I need your help there.

One thing more, let's say, when I write the blue line in Dev-C++ it never ends. I have to scroll left and right to see the line. Isn't there some way that I could wrap this lengthy line into sections as they appear here? Do you get what I'm saying?

Please now help me.

Code:

#include <iostream>
#include <conio.h>

int main()

{
	char r;
	cout << "Enter the letter" << endl;
	cin >> r;
	if ( (r=='A')||(r=='B')||(r=='C')||(r='D')||(r=='E')||(r=='F')||(r=='G')||(r=='H')||          
        (r=='I')||(r=='J')||(r=='K')||(r=='L')||(r=='M')||(r=='N')||(r=='O')||(r=='P')||(r=='Q')||    
        (r=='R')||(r=='S')||(r=='T')||(r=='U')||(r=='V')||(r=='W')||(r=='X')||(r=='Y')||(r=='Z') )
	        cout << "r is uppercase" << endl;
	
        else if ( (r=='a')||(r=='b')||(r=='c')||(r='d')||(r=='e')||(r=='f')||(r=='g')||(r=='h')||  
        (r=='i')||(r=='j')||(r=='k')||(r=='l')||(r=='m')||(r=='n')||(r=='o')||(r=='p')||(r=='q')|| 
        (r=='r')||(r=='s')||(r=='t')||(r=='u')||(r=='v')||(r=='w')||(r=='x')||(r=='y')||(r=='z') )
	        cout << "r is lowercase" << endl;
	
        else
	if (r is a real number)
	else
	???
	getch();
}

Take a look in the C headers for isalpha(), isupper(), islower(), isdigit() and atof().
Might make your life a little easier.

Originally Posted by jackson6612

One thing more, let's say, when I write the blue line in Dev-C++ it never ends. I have to scroll left and right to see the line. Isn't there some way that I could wrap this lengthy line into sections as they appear here? Do you get what I'm saying?

There's nothing stopping you from wrapping it like you have in the code you posted here. There's nothing in C++ that says the condition in an if statement has to be on one line.

Hi again

This is a better and simple program which I've written after guidance from you guys. Why do I have to enclose A, Z, 0, and 9 within single quotes? Otherwise my code didn't work. (Mozza, I'm sorry if there is a problem with indentation. I don't know something goes wrong when I paste the code here.).

Code:

#include <iostream>
#include <conio.h>

using namespace std;

int main()

{
	char r;
	cout << "Input = " ;
	cin >> r;
	if ( r >= 'A' && r <= 'Z')
	   cout << "the entry is a capital letter" << endl;
        else if ( r >= 'a' && r <= 'z' )
           cout << "the entry is a small letter" << endl;
        else if ( r >= '0' && r <= '9' )
          cout << "the entry is a digit" << endl;
        else 
         cout << "Input error" << endl;
 
    getch();
}

Why do I have to enclose A, Z, 0, and 9 within single quotes?

The single quotes denote a char constant.

Example

Code:

char ch = 'A';

Jim

Originally Posted by jimblumberg

The single quotes denote a char constant.

Example

Code:

char ch = 'A';

Jim

Thanks, Jim.

In the following processing statement "3.142" is also constant.

Code:

A = 3.142*r*r

How does a character constant differ from a general constant? Perhaps, a character constant is special standardized constant which has a symbol, used with single quotes and recognized by the system.

I suspect ASCII standardizes these constants and allots them symbols.
Ascii Table - ASCII character codes and html, octal, hex and decimal chart conversion

Please correct me. Thank you.

Regards
Jackson

Originally Posted by jackson6612

Why do I have to enclose A, Z, 0, and 9 within single quotes? Otherwise my code didn't work.

Good question. The reason is that when you want the actual character, J, for example, the compiler needs to know that you mean J the character and not J the variable. E.g.:

Code:

int main()
{
    int J = 3;
    cout << J << endl; // outputs 3
    cout << 'J' << endl; // outputs J
    return 0;
}

Of course it's conceivable you could make a language in which if there was no variable J available then

Code:

cout << J << endl;

would output J the character instead. However, this makes code difficult to read because someone reading it who hasn't seen the whole program will probably expect J stores some value that is being printed. For this reason, in C++ and other languages, you need to put quotes around the letter whenever you mean the letter itself and not a variable.

Originally Posted by Mozza314

Good question. The reason is that when you want the actual character, J, for example, the compiler needs to know that you mean J the character and not J the variable. E.g.:

Code:

int main()
{
    int J = 3;
    cout << J << endl; // outputs 3
    cout << 'J' << endl; // outputs J
    return 0;
}

Of course it's conceivable you could make a language in which if there was no variable J available then

Code:

cout << J << endl;

would output J the character instead. However, this makes code difficult to read because someone reading it who hasn't seen the whole program will probably expect J stores some value that is being printed. For this reason, in C++ and other languages, you need to put quotes around the letter whenever you mean the letter itself and not a variable.

Yes, I think I understand it now. Thanks Mozza. You have been very helpful through out without any air of arrogance!

Okay, when I use double quotation marks I have text
When I simply enter something, such as A, B, C, etc, it is expected to be a variable.
When I use single quotes then it's a character constant - a constant of special type which has a particular symbol and recognized by the system. But what if I try to use some self-invented character symbol (I see '+' is also taken as a character) which has been standardized by ASCII, then would it give error?

Is this correct? Please correct me if I'm wrong.


Now some more questions. My questions will appear in the code following "//". It would be nice of you if you could shed some light. (sorry, if there is a big issue with indentation, when I copy the code here something goes wrong)

Code:

#include <iostream>
# include <cmath>
#include <cstdlib> // these are header files?

using namespace std; // this is "using" statement?

int main () // this is the function which we are using?

{
    float a, b, c, R1, R2; // this is the declaration statement?
    
    system("Color 1A"); // this is what? I use it to change the color of the console.
    
    cout << "Enter a, b, c of the equation ax^2 + bx + c = 0" << endl;
    cout << "Enter a = ";
    cin >> a; // what are cout and cin statements called?
    
    cout << "Enter b = ";
    cin >> b;
    
    cout << "Enter c = ";
    cin >> c;
    
	float D = b*b - 4*a*c; // this both declaration and processing statement?
    if (D >= 0)
    {
        cout << "R1 is = " << ( -b + sqrt(D) )/( 2*a ) << endl;
        cout << "R2 is = " << ( -b - sqrt(D) )/( 2*a ) << endl;
    } // this is if statement?
    
	else
    {
        cout << "no real roots exist" << endl;
    }
    
    system("PAUSE"); // what would called this? "system" specific statement?
}

Originally Posted by jackson6612

When I simply enter something, such as A, B, C, etc, it is expected to be a variable.
When I use single quotes then it's a character constant - a constant of special type which has a particular symbol and recognized by the system. But what if I try to use some self-invented character symbol (I see '+' is also taken as a character) which has been standardized by ASCII, then would it give error?

What do you mean "self-invented"? '+' is a perfectly normal character. The single quotes don't just apply to letters. In the case of '+', you're telling the compiler that you mean '+' the character and not + the operator that adds numbers together.

Originally Posted by jackson6612

Code:

#include <iostream>
# include <cmath>
#include <cstdlib> // these are header files?
// Yes

using namespace std; // this is "using" statement?
Yes; it makes everything in the namespace std accessible without prefixing it with "std::".
// E.g. without it you'd have to write "std::cout" in place of "cout".

int main () // this is the function which we are using?
// Yes; main() is a special function which is marks the start of execution of the program
{
    float a, b, c, R1, R2; // this is the declaration statement?
    // This is where you create the float variables, it's known as "declaration", yes
    
    system("Color 1A"); // this is what? I use it to change the color of the console.
    // What's your question? It's a call to the function system().
    
    cout << "Enter a, b, c of the equation ax^2 + bx + c = 0" << endl;
    cout << "Enter a = ";
    cin >> a; // what are cout and cin statements called?
    // They don't really have a special name. ">>" is sometimes called the
    // extraction operator and "<<" the insertion operator if that's what you're asking.
    
    cout << "Enter b = ";
    cin >> b;
    
    cout << "Enter c = ";
    cin >> c;
    
    float D = b*b - 4*a*c; // this both declaration and processing statement?
    // Yes, the value b*b - 4*a*c is calculated and then D is initialised with that value
    if (D >= 0)
    {
        cout << "R1 is = " << ( -b + sqrt(D) )/( 2*a ) << endl;
        cout << "R2 is = " << ( -b - sqrt(D) )/( 2*a ) << endl;
    } // this is if statement? it's the end of the block associated with the if statement
    else
    {
        cout << "no real roots exist" << endl;
    }
    
    system("PAUSE"); // what would called this? "system" specific statement?
    // Could you rephrase that? I don't understand what you're asking.
}

Thanks a lot, Mozza. It was really helpful and have to say it again that you are very nice. My best wishes.

What do you mean "self-invented"? '+' is a perfectly normal character. The single quotes don't just apply to letters. In the case of '+', you're telling the compiler that you mean '+' the character and not + the operator that adds numbers together.

What about the character '++'. Isn't it self-invented?

In one of the post above I used this:

Code:

if ( r >= 'A' && r <= 'Z')

The above if condition is valid because ASCII has the values of "A" and "Z" in a sequence (decimal values: 65-90). Instead if I had written something like:

Code:

if ( r >= 'A' && r <= '8')

Then it isn't a valid condition because "8" has decimal value of 56 on ASCII table. It's like saying something like this: r >= 65 and r <= 56. I hope you understand what I'm trying to ask. Please correct me where I'm wrong or missing something.

But this also begs another question. What if I know the ASCII code of some character but don't have a key for that character on the keyboard, let's say PI which has ASCII decimal code of 227?

ASCII table: http://www.asciitable.com/

int main() is a function and so is system() as you say. But wouldn't it make "system()" a sub-function because it's included in the body - the body being {...} - of "int main()"?

Best regards
Jackson

Originally Posted by Mozza314

Now, what stands out to me here is that you can use <, <=, >, >= on char values to test ranges just like with numbers, but it appears you don't know this. It means you can replace:

Incidentally, though it does not matter in practice these days, in theory the English letters in the character set need not be in contiguous and in alphabetical order. You do have this guarantee of order and contiguous placement for the digits though.

Originally Posted by jackson6612

But what if I try to use some self-invented character symbol (I see '+' is also taken as a character) which has been standardized by ASCII, then would it give error?

Originally Posted by jackson6612

What about the character '++'. Isn't it self-invented?

Turn up your compiler warning level and attempt to compile some code like that. Then, if the compiler does not react as you expect, ask us why.

Originally Posted by jackson6612

Then it isn't a valid condition because "8" has decimal value of 56 on ASCII table. It's like saying something like this: r >= 65 and r <= 56.

It is still a valid condition, except that it always evaluates to false.

Originally Posted by jackson6612

What if I know the ASCII code of some character but don't have a key for that character on the keyboard, let's say PI which has ASCII decimal code of 227?

Then you do something depending on what you are trying to do.

Hint: "what if" questions are nice for you to think out loud, but they require the reader to guess what your thoughts are if you don't actually think out loud your entire train of thoughts. Imagine going to a shop to buy a drink, and you ask the storekeeper "what if I bought this can of coke?" The storekeeper would have to figure out if he should say "then you have to pay me $1" or if he should say "then you would be missing out on this beer" (i.e., he has to figure out whether you are really asking how much it costs, or if you are asking his opinion on what drink to buy).

Originally Posted by jackson6612

int main() is a function and so is system() as you say. But wouldn't it make "system()" a sub-function

The term "sub-function" does not exist in standard C++, so you should explain what you understand by that term.