Our clients (and some of our interns) often ask which programming languages are the easiest to learn, but at least a couple times each month we get questions about  which programming languages are especially hard to learn. People have some pretty strong (and very different!) opinions about this, so there’s no perfect list, but here are a few of the especially tough ones, along with what they’re used for, which major companies use them, and why they’re so difficult.

Assembly Language

Want to get as down to the nuts and bolts as possible when it comes to programming? Well, here it is.

Assembly language is a low-level programming language that is used to write the programs that interact with hardware — we’re talking the actual devices that run everything else, like microcontrollers, embedded systems, and operating systems. Assembly language requires developers to have a deep understanding of the underlying hardware, which can make it challenging to learn. (Low-level languages, such as assembly language, are closer to machine code, while high-level languages, such as Python or Java, abstract away much of the hardware details and allow developers to write more readable and maintainable code.) 

Additionally, assembly language lacks high-level programming constructs out of the box, such as loops and conditionals, making it more difficult to write complex programs. Loops and conditionals are programming constructs used to control the flow of a program, with loops repeating a set of instructions and conditionals allowing for different actions to be taken based on a set of criteria.

Major companies that use assembly language include Intel, Apple and Microsoft.

Haskell

Haskell is a functional programming language that is used for mathematical modeling, scientific computing and artificial intelligence. Haskell developers have to think in a fundamentally different way than with imperative languages such as Java or Python. (An imperative language is a programming language that follows a procedural approach, where the programmer specifies a sequence the computer must follow to solve a problem.) 

Haskell emphasizes programming concepts including  immutability, purity and laziness, which can be challenging for developers who are used to imperative programming. Immutability involves creating variables and functions that cannot be changed once created, while “purity” refers to the property of a function that does not have any side effects, acting in the mathematical sense and always delivering the same result for the same input. “Laziness” refers to a technique in functional programming where an expression is not evaluated until it is actually needed.

Major companies that use Haskell include Facebook, GitHub, Microsoft, Tesla and Galois.

C++

C++ is a general-purpose programming language that is used for developing system software, game engines and high-performance applications. C++ has complex syntax and a steep learning curve. Also, C++ requires developers to manage memory manually, which can lead to memory leaks and other issues.

Major companies that use C++ include Google, Amazon, and Microsoft.

Prolog

Prolog is a logic programming language that is used for artificial intelligence, natural language processing and expert systems. Prolog requires developers to think in terms of rules, facts and relationships. It also uses a unique syntax and requires developers to learn new concepts such as backtracking and unification. (Backtracking is a technique used to find a solution by trying out different possibilities and backtracking to previous steps if necessary. Unification is a process in logic programming where two expressions are matched together and variables are assigned to values in a way that makes them equivalent.)

Major companies that use Prolog include Siemens and IBM.

Rust

Rust is a systems programming language developed by Mozilla that is designed for speed, safety and concurrency. (Concurrency in programming is the ability to execute multiple tasks or processes at the same time, allowing for better use of resources and increased program efficiency.) 

Rust developers have to understand Rust-unique programming concepts like ownership, borrowing and lifetimes. (Ownership defines which part of the code “owns” a given piece of memory, borrowing specifies how other parts of the code can temporarily access that memory, and lifetimes are a way to determine that a reference is not used after the data it points to has been deallocated.) 

Rust’s borrow checker enforces strict rules to prevent data races and memory bugs, common issues in concurrent programming that occur when two or more threads access the same memory location simultaneously, leading to unpredictable behavior and potentially crashing the program.

Major companies that use Rust include Dropbox, Mozilla and Microsoft.

Why are these languages so difficult?

So what makes a programming language legendarily difficult? In some cases, it’s because they require a deep understanding of hardware or underlying systems. Others require developers to think in completely different ways than almost every other programmer. Some can chalk up their notoriety to complex syntax, steep learning curves or memory management.

But even though they’re among the hardest to learn, these languages are also widely used by major companies for various purposes, and the developers who are fluent in them and up to the challenge often find their skills in high demand.

But no one expects you to learn hard skills yourself — because that’s what insanely talented developers like the ones at Plan A are for.