What Is an Integer in Programming?

What an integer is

An integer is a data type that represents whole numbers, numbers with no fractional or decimal part. Values like 0, 7, 42, and -15 are integers; 3.14 is not. Integers are one of the most basic and widely used data types in programming, because so much of what programs do involves counting and whole quantities: the number of items in a cart, a person's age, a score in a game, or a position in a list.

Integers vs. decimals

The key distinction is that integers have no fractional part, while 'floating-point' numbers do. Use an integer when you are counting discrete things, you cannot have 2.5 people in a room or 3.7 items in a cart. Use a floating-point number when you need fractions or measurements, like a price of 9.99 or a temperature of 98.6. Choosing the right type matters: integers are exact and efficient for whole-number work, which is exactly what counting requires.

Why integers are special

Integers have an important advantage: they are exact. Whole numbers can be represented precisely in a computer, so integer arithmetic gives exact results with no rounding. This is different from floating-point numbers, which can have tiny rounding errors. When you need exact, reliable whole-number math, counting, indexing, or anything where precision matters, integers are the right and safe choice. Their exactness is a big part of why they are so fundamental.

Size limits and overflow

Integers are stored using a fixed amount of memory, which means there is a limit to how large (or small) a value they can hold. If a calculation produces a number beyond that limit, you get 'overflow,' where the value wraps around or behaves unexpectedly. Many languages offer integers of different sizes to handle larger ranges. Understanding that integers have limits, and that overflow can happen, helps programmers avoid a subtle but real source of bugs.

Signed and unsigned

Integers can be 'signed' or 'unsigned.' Signed integers can represent both positive and negative numbers, which is the default in most situations. Unsigned integers represent only non-negative numbers, but in exchange can reach a higher maximum value for the same amount of memory. The choice depends on whether you need negative numbers and how large your values might get. This is a small but practical detail of how integers work under the hood.

Why it matters

Integers are among the first and most important data types every programmer uses, because counting and whole-number math are everywhere in software. Understanding them, how they differ from decimals, why they are exact, and that they have size limits, builds a solid foundation for working with numbers in code. For anyone learning programming, integers are a basic but essential concept that comes up in virtually every program you will ever write.

Related on Skillo

See also: What is a data type? Explained simply, What is binary code? Explained simply.

Sources

• Integer (computer science) - Wikipedia

Published date reflects the original event date (2024-06-18). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.