Data

Data is a broad term that refers to all types of information. The string hemanta is a piece of data. The number 26 is also a piece of data. In fact, most complex pieces of data are nothing but a combination of strings and numbers.

Data structure

Data structure refers to how data (information) is organized. Look at the code snippet below:

const firstName = "hemanta"
const lastName = "sundaray"

console.log(`${firstName} ${lastName}`)
// hemanta sundaray

We have written a program that stores two pieces of data in two variables and outputs a single piece of data. We can also choose to store the same data as elements of an array:

const person = ["hemanta", "sundaray"]

console.log(`${person[0]} ${person[1]}`)
// hemanta sundaray

As you can see, data can be organized in various ways. The reason we must pay careful attention to data organization is because it can have a significant impact on how fast our program runs.

Measuring fastness of programs

When we say fast, we don’t refer to how fast a program runs in terms of pure time. Instead, we refer to how many steps a program takes.

Why do we measure the performance of programs in terms of steps, not time?

Because, time can vary depending on the hardware a program runs on. For example, a program that takes 2 seconds to run on a regular desktop computer can take a fraction of a millisecond on a supercomputer.

However, when we measure the performance of a program in terms of how many steps it takes, and we find out, for example, that program A takes 5 steps in comparison to another program B that takes 500 steps to find the solution, we can say that program A will always be faster than program B irrespective of the hardware. This is the reason why we measure the performance of programs in terms of steps, not in terms of time.

Time complexity

This measurement of performance of a piece of code is what is known as time complexity. You will also come across people using the term runtime complexity. They both refer to the same thing – the number of steps a program or an operation takes.