C Data Types
Data Types
As explained in the Variables chapter, a variable in C must be a specified
data type,
and you must use a format specifier inside the printf() function to display it:
Example
// Create variables
int myNum = 5; // Integer (whole number)
float
myFloatNum = 5.99; // Floating point number
char myLetter = 'D'; //
Character
// Print variables
printf("%d\n", myNum);
printf("%f\n", myFloatNum);
printf("%c\n", myLetter);
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Basic Data Types
The data type specifies the size and type of information the variable will store.
In this tutorial, we will focus on the most basic ones:
| Data Type | Size | Description |
|---|---|---|
int |
2 or 4 bytes | Stores whole numbers, without decimals |
float |
4 bytes | Stores fractional numbers, containing one or more decimals. Sufficient for storing 6-7 decimal digits |
double |
8 bytes | Stores fractional numbers, containing one or more decimals. Sufficient for storing 15 decimal digits |
char |
1 byte | Stores a single character/letter/number, or ASCII values |
Basic Format Specifiers
There are different format specifiers for each data type. Here are some of them:
| Format Specifier | Data Type | Try it |
|---|---|---|
%d or %i |
int |
Try it » |
%f |
float |
Try it » |
%lf |
double |
Try it » |
%c |
char |
Try it » |
%s |
Used for strings (text), which you will learn more about in a later chapter | Try it » |
Set Decimal Precision
You have probably already noticed that if you print a floating point number, the output will show many digits after the decimal point:
Example
float myFloatNum = 3.5;
double myDoubleNum = 19.99;
printf("%f\n", myFloatNum);
// Outputs 3.500000
printf("%lf", myDoubleNum); // Outputs
19.990000
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If you want to remove the extra zeros (set decimal precision), you can use a
dot (.) followed by a number that specifies how many digits that should be shown
after the decimal point:
Example
float myFloatNum = 3.5;
printf("%f\n", myFloatNum);
// Default will show 6 digits after the decimal point
printf("%.1f\n",
myFloatNum); // Only show 1 digit
printf("%.2f\n", myFloatNum); // Only
show 2 digits
printf("%.4f", myFloatNum); // Only show 4 digits
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Real-Life Example
Here's a real-life example of using different data types, to calculate and output the total cost of a number of items:
Example
// Create variables of different data types
int items = 50;
float
cost_per_item = 9.99;
float total_cost = items * cost_per_item;
char
currency = '$';
// Print variables
printf("Number of items: %d\n",
items);
printf("Cost per item: %.2f %c\n", cost_per_item, currency);
printf("Total cost = %.2f %c\n", total_cost, currency);
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