Loops
Oftentimes, programmers need to repeat a certain block of code multiple times.
Since code repetition is impractical and also a bad practice, most programming languages provide a concept called loop, which helps in executing one or more statements up to a desired number of times until a certain condition is reached.
An early form of loop (available both in C and C++ but not in other languages like Java and Python) was the goto statement, which transfers the program's flow to another line of code using labels. Although used a lot in the past, goto statements are rarely useful and not recommended since they lead to spaghetti code (unreadable code with a path of execution similar to a bowl of spaghetti, all tangled and twisted) and don't fit with the structured programming paradigm we now use.1
"The fact that 'goto' can do anything is exactly why we don't use it" —Bjarne Stroustrup (creator of C/C++)
Loops are a better alternative and they come in various forms:
- For loop
- While loop
- Do-while loop
These three types of loops are a little different from each other, but they all have one fundamental thing in common: the code inside the loop is repeatedly executed, whether a specified number of times or until some condition is met, or even indefinitely.
In the next sections we'll discuss how these loops work exactly.