LESSON 5/53Storing Information

Other Types

GOALStore decimals, letters, words and true/false.

Not everything is a whole number. Each box must know what kind of thing it holds.

ON THIS PAGE

The example
Line by line
Watch it run
Whole numbers
Numbers with a decimal point
Booleans (bool)
Single characters (char)
Which type should I use?
Common mistakes
Quick check

SHOW EXAMPLE IN

//THE EXAMPLE

main.cpp

#include <iostream>
using namespace std;

int main() {
    int   count  = 7;
    double price = 19.5;
    char  grade  = 'A';
    bool  passed = true;
    string name  = "Saraa";

    cout << name << " got " << grade << endl;
    cout << "Price: " << price << endl;
    cout << "Passed? " << passed << endl;
    return 0;
}

> what you see

Saraa got A
Price: 19.5
Passed? 1

Try this code

//LINE BY LINE

double price = 19.5;

double holds decimals. An int would chop 19.5 down to 19.

char  grade  = 'A';

char is a SINGLE letter. It uses single quotes ' '.

bool  passed = true;

bool is only true or false. It prints as 1 (true) or 0 (false).

string name  = "Saraa";

A string is a word or sentence. It uses double quotes " ".

Watch it run

An int box has a fixed edge. big = 2 000 000 000 only just fits inside it.

1 / 4

Whole numbers

An int holds numbers between about ±2 billion. For anything bigger use long long.

Type	Range
`int`	≈ −2 000 000 000 … 2 000 000 000
`long long`	≈ ±9 000 000 000 000 000 000
`unsigned int`	0 … ≈4 000 000 000 (сөрөг үгүй / no negatives)

Going past the limit makes the number wrap around to a negative. Use long long when products get large.

int big = 2000000000;
big = big + big;              // хэтэрлээ — хог утга

long long safe = 2000000000;
safe = safe + safe;           // ✓ 4000000000

Numbers with a decimal point

A double holds numbers with a decimal point: 3.14, -0.5, 2.0. There is also float, but it is less precise — prefer double.

double price = 19.99;
double half = 7 / 2.0;        // 3.5
cout << half << endl;

> what you see

3.5

Decimals are stored approximately, not exactly. So 0.1 + 0.2 == 0.3 can be false. Never compare decimals with ==.

Booleans (`bool`)

A bool has just two values: true and false. Every comparison you write produces a bool.

bool isRaining = true;
bool passed = (score >= 60);   // харьцуулалтын хариу

cout << isRaining << endl;     // 1 гэж хэвлэнэ
cout << boolalpha << isRaining;// true гэж хэвлэнэ

C++ prints a bool as a number: true is 1, false is 0. Use boolalpha if you want the words.

Single characters (`char`)

A char holds one character. It uses single quotes: 'A'. Double quotes "A" make a string, not a character.

char grade = 'A';
char digit = '7';

cout << grade << endl;        // A
cout << (int)grade << endl;   // 65 — ASCII дугаар

> what you see

A
65

Every character is really a number underneath (its ASCII code). So 'a' + 1 gives 'b', and '5' - '0' gives the number 5.

Which type should I use?

What you are storing	Type
Хүний нас, тоо ширхэг / a count or age	`int`
Маш том тоо / a very large number	`long long`
Үнэ, дундаж, хэмжээ / a price or average	`double`
Тийм/үгүй / yes or no	`bool`
Нэг үсэг / one letter	`char`
Үг, өгүүлбэр / a word or sentence	`string`

//COMMON MISTAKES

✗ wrong

char grade = "A";

✓ right

char grade = 'A';

char uses single quotes; string uses double quotes.

✗ wrong

int price = 19.5;

✓ right

double price = 19.5;

int throws the decimal away and stores 19.

//QUICK CHECK

Which type stores a height like 1.62?

Variables Reading Input

//THE EXAMPLE

main.cpp

#include <iostream>
using namespace std;

int main() {
    int   count  = 7;
    double price = 19.5;
    char  grade  = 'A';
    bool  passed = true;
    string name  = "Saraa";

    cout << name << " got " << grade << endl;
    cout << "Price: " << price << endl;
    cout << "Passed? " << passed << endl;
    return 0;
}

> what you see

Saraa got A
Price: 19.5
Passed? 1

Try this code

//LINE BY LINE

double price = 19.5;

double holds decimals. An int would chop 19.5 down to 19.

char  grade  = 'A';

char is a SINGLE letter. It uses single quotes ' '.

bool  passed = true;

bool is only true or false. It prints as 1 (true) or 0 (false).

string name  = "Saraa";

A string is a word or sentence. It uses double quotes " ".

Whole numbers

An int holds numbers between about ±2 billion. For anything bigger use long long.

Type	Range
`int`	≈ −2 000 000 000 … 2 000 000 000
`long long`	≈ ±9 000 000 000 000 000 000
`unsigned int`	0 … ≈4 000 000 000 (сөрөг үгүй / no negatives)

Going past the limit makes the number wrap around to a negative. Use long long when products get large.

int big = 2000000000;
big = big + big;              // хэтэрлээ — хог утга

long long safe = 2000000000;
safe = safe + safe;           // ✓ 4000000000

Numbers with a decimal point

A double holds numbers with a decimal point: 3.14, -0.5, 2.0. There is also float, but it is less precise — prefer double.

double price = 19.99;
double half = 7 / 2.0;        // 3.5
cout << half << endl;

> what you see

3.5

Decimals are stored approximately, not exactly. So 0.1 + 0.2 == 0.3 can be false. Never compare decimals with ==.

Booleans (bool)

A bool has just two values: true and false. Every comparison you write produces a bool.

bool isRaining = true;
bool passed = (score >= 60);   // харьцуулалтын хариу

cout << isRaining << endl;     // 1 гэж хэвлэнэ
cout << boolalpha << isRaining;// true гэж хэвлэнэ

C++ prints a bool as a number: true is 1, false is 0. Use boolalpha if you want the words.

Single characters (char)

A char holds one character. It uses single quotes: 'A'. Double quotes "A" make a string, not a character.

char grade = 'A';
char digit = '7';

cout << grade << endl;        // A
cout << (int)grade << endl;   // 65 — ASCII дугаар

> what you see

A
65

Every character is really a number underneath (its ASCII code). So 'a' + 1 gives 'b', and '5' - '0' gives the number 5.

Which type should I use?

What you are storing	Type
Хүний нас, тоо ширхэг / a count or age	`int`
Маш том тоо / a very large number	`long long`
Үнэ, дундаж, хэмжээ / a price or average	`double`
Тийм/үгүй / yes or no	`bool`
Нэг үсэг / one letter	`char`
Үг, өгүүлбэр / a word or sentence	`string`

Other Types

//THE EXAMPLE

//LINE BY LINE

Watch it run

Whole numbers

Numbers with a decimal point

Booleans (bool)

Single characters (char)

Which type should I use?

//COMMON MISTAKES

//QUICK CHECK

Other Types

//THE EXAMPLE

//LINE BY LINE

Watch it run

Whole numbers

Numbers with a decimal point

Booleans (bool)

Single characters (char)

Which type should I use?

//COMMON MISTAKES

//QUICK CHECK

Booleans (`bool`)

Single characters (`char`)

Booleans (`bool`)

Single characters (`char`)