Char data Type

The data types we introduced in the second chapter were broadly classified into: integer and real. Types of presented whole data were differentiated only by the number of bytes occupied by the variables: short and unsigned short – on 2 bytes, int and unsigned int on 4 bytes, long long and unsigned long 8 bytes long.

There is also one byte integer data type and that is the char type. Now the question arises why the char type does not a was presented together with the other whole types. The reason is that the char data type was intended for something rather than storing integer values ​​on a byte. It also allows working with symbols and more the basis of working with words.

On this site we deal with the rules that must be taken into account in order to understand how to manipulate correctly char data.

Being therefore an integer type on one byte, we have the types:

The following applies whether we are talking about the char type or about unsigned char (obviously, except for the range of values ​​that a variable can take, as shown above).

Here are some examples

We consider them in the context of the statements:

char a, b;
int x;

a = 10;
b = a * 2;

What's so special about the char data type, though?

As I said above, through it we can work in C/C++ with symbols and words. By convention, each symbol has an associated numerical code called its ASCII code. This code is the stored numerical value when storing the symbol in RAM or on external media. Here are some codes associated with the symbols:

97 for a
65 for A
48 for 0
32 for space

Also, the other letters of the alphabet have consecutive codes, i.e. b has 98, c has 99, B has 66, C has 67 etc. We notice from now on, and it's good to remember, that we have larger codes for lowercase letters than for capital letters.

Here are the three special things about char data:

1. Char constants can also be written by putting a symbol between apostrophes. Here are some examples:

We consider the declaration:

char a, b;
int x;

‘ a ’  ‘ C ’  ‘ & ’  ‘ 2 ’ 

In conclusion, writing a symbol between apostrophes is another way to specify an integer value constant (note that all integer operations are allowed).

2. When displaying with cout a data of type char, specified explicitly as char, it is displayed on the screen the symbol whose code is the numerical value stored in the data of char type.

Let's explain more precisely what we mean when we say that the date to be displayed should be indicated exactly as type char: variable of type char given as a parameter on display, constant written according to the rule of the symbol between apostrophes, expression preceded by the char conversion operator, or a function that returns a date of type char.

We must keep in mind the following: if the char date appears in an expression alongside other dates and operators, the result is automatically converted to int even though the result could be stored on a byte. So the language works when applying operators, so it tries to do all calculations in the most data type comprehensive, and if this is int or less than int, calculations are done in int. In these cases the result is therefore considered to be of type int and the numeric value will be printed instead of the symbol. Here are some examples.

We consider the declaration:

char a, b;
int x;

a = ‘c’;
cout << a; 

a = 99;
cout << a;

a = ‘ ’;
x = a;
cout << x;

3. When reading with cin, if the parameter is a char variable, what is entered from the keyboard is interpreted as a symbol.

We consider the declaration:

char a, b;

cin>>a;
cout << a;

cin>>a>>b;
cout << a << ” ” << b << ” ” << a + b;

cin>>a>>b;
cout << a << ” ” << b << ” ” << a+b;

cin >> a;

The main conclusion should be that char data is stored as numbers, allow use operators generally applicable to whole data, but to interaction with input/output devices, i.e. to read/write, they are interpreted as symbols. Also, there is the special option to indicate the constants of type char (symbol placed between apostrophes).

Writing char constants for special characters.

For the codes from 0 to 31 there are no associated symbols specified in the standard. Characters with these codes they generally have other specifications and not the printing of a particular symbol on the screen. That's why we can't use them specific writing to constants because we simply don't have anything to put between apostrophes as a symbol. There is however a convention that allows us to also refer to them as constants of type char: the escape sequences

An escape sequence is specified by multiple symbols between apostrophes, the first symbol being \ (backslash). Even if several symbols are written, we should not think that it would be several characters, it is about only one but indicated in a certain way.

Here are the escape sequences for some special characters:

‘ \n ’

Among these characters, enter is often used, for the others I presented the effect maybe more like fun

If we run the following code, the results will be seen in the console capture shown on the right.

cout << "*" << '\n' << (int)'\n' << "*\n";
cout << "*" << '\t' << (int)'\t' << "*\n";
cout << "*" << '\b' << (int)'\b' << "*\n";
cout << "*" << '\a' << (int)'\a' << "*\n";

*
10*
*         9*
8*
*7*

On each line of code we wrote the print of a character as a "symbol" followed by its ASCII code, the two framed by two star characters.

Let's explain what is on the right. The enter character moves the cursor to the next line, so it stays on the first line only one asterisk, and on the second one, from the beginning is the enter code (10) and the final asterisk of the first line of code.

We have printed a line break for each instruction, so for the next symbol a new line is passed. There we notice a large space between the first star and 9, that is, the tab "symbol" followed by its code was displayed.

On the next line of the screen are those produced by the third line of code. The starting asterisk was displayed, but typing the backspace "symbol" moved the cursor under it. Then when displaying the backspace code (8) it a overwrite it. On the last line only 7 appears between the asterisks because the effect of printing the symbol is actually the sound produced.

Three other particular escape sequences can be used for apostrophe characters, quotation marks, and backspace. They are write preceded by a backslash.

How do we refer as characters to the others that have codes between 0 and 31? Here we have presented only 4 of them non-displayable characters. The answer comes from the general form of writing escape sequences: between apostrophes, with backspace in front, we can write a code in base 8. That is, writing in base 8 ASCII code. In the this way we can indicate all characters, including those with associated symbol, as escape sequences.

Example:

cout << ’ \141 ’;

cout << ’ * ’ << ’ \12 ’ << ’ * ’;

cout << ’ \n ’ + ‘ a ’ + ‘ \11 ’;

Exercises and solved problems:

1. Having stored the code of a small letter of the alphabet in the variable x of char type, change it to memorize the corresponding capital letter code.

Solution:

x = x – ( ‘ a ’ – ‘ A ’ );

Instead of ' a ' - ' A ' we could write ' b '- ' B ' or ' p ' - ' P ' or any difference between the codes of a pair lower case - upper case identical. This is because this difference is constant and we also need to know that lowercase letters have larger codes than uppercase ones. This difference is 32 but we don't so we have to keep this in mind.

2. Having stored in the char variable x the code of a small letter of the alphabet, to display it on the screen the next letter in the alphabet (or a message if already x stores the value of the last letter).

Solution:

if (x == ‘z’)
    cout << ”ultima”;
else
    cout << (char)(x+1);

3. A char date is read from the keyboard. Display the message YES if a lowercase letter a was entered alphabet or the message NO if something else was entered.

Solution:

The lowercase letters of the alphabet have ASCII codes in a range, so the test is equivalent to just comparing with the edges. It is not necessary to know the ASCII codes of the first and last letter, it is enough to write symbol between the apostrophes because we have determined that the operators apply to the numeric code anyway.

#include <iostream>
using namespace std;
char x;
int main () {
cin>>x;
if (x >= 'a' && x <= 'z')
    cout << "DA";
else
    cout << "NU";
return 0;
}

4. A char date is read from the keyboard. Display the letter message if a letter a has been entered alphabet (uppercase or lowercase), the digit message if a digit symbol has been entered, or the message else in another case

Solution:

#include <iostream>
using namespace std;
char x;
int main () {
cin >> x;
if ((x >= 'A' && x <= 'Z') || (x >= 'a' && x <= 'z'))
    cout << "litera";
else
if (x >= '0' && x <= '9')
    cout << "cifra";
else
    cout << "altceva";
return 0;
}

Uppercase and lowercase letters represent two code ranges. So the letter test comes down to testing if we are in one of these ranges. Knowing that the big letters have the smaller codes, maybe we are tempted to we write (x >= 'A' && x <= 'z'). This is not correct as the two intervals are not contiguous. Being 26 letters, A having the code 65, we get that Z has the code 90. So from 91 to 96 there are other characters (97 is the code for a).

We have to be careful with the digit test because apostrophes are often overlooked. It is not receiving compile error but it also doesn't compare to what we would like (ASCII code of the symbol).

5. A char date is read from the keyboard. Check if it represents a lowercase vowel.

Solution:

#include <iostream>
using namespace std;
char x;
int main () {
    cin>>x;
if (x=='a'||x=='e'||x=='i'||x=='o'||x=='u')
    cout << "este vocala";
else
    cout << "nu este vocala";
    return 0;
}

The ASCII codes of the vowels are not consecutive so we can no longer put the condition of belonging to a character to a range. Being only 5 vowels we can write a condition composed of 5 others connected by ||. If we would have to test if the read character is consonant, we should not rush to consider that it is correct just deny the above condition. That would just mean it's not a vowel. We need to bond with && negating the condition above from the condition that the character to be tested is lowercase.