Numbers

Numeric Types

Use int when you need to store a whole number without decimals, like 35 or 1000, and float or double when you need a floating point number (with decimals), like 9.99 or 3.14515.

int

int myNum = 1000;
printf("%d", myNum);

float

float myNum = 5.75;
printf("%f", myNum);

double

double myNum = 19.99;
printf("%lf", myNum);

Note: float vs. double The precision of a floating point value indicates how many digits the value can have after the decimal point. The precision of float is six or seven decimal digits, while double variables have a precision of about 15 digits. Therefore, it is often safer to use double for most calculations - but note that it takes up twice as much memory as float (8 bytes vs. 4 bytes).

Scientific Numbers

In C, you can write very large or very small floating-point numbers using scientific notation.

This is done using the letter e (or E), which stands for "times 10 to the power of".

For example, 35e3 means 35 × 10³ = 35000.

This is useful for writing numbers in a shorter way. Especially when working with scientific values or large-scale data.

Example

float f1 = 35e3;   // 35 * 10^3 = 35000
double d1 = 12E4;  // 12 * 10^4 = 120000

printf("%f\n", f1);
printf("%lf", d1);