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Fortran Interview Questions and Answers

This page provides a comprehensive collection of Fortran Interview Questions and Answers designed for students, fresh graduates, software developers, scientific programmers, and experienced engineers preparing for technical interviews. The questions range from beginner to advanced level and include practical explanations that help you understand modern Fortran programming.

Although Fortran is one of the oldest programming languages, it remains widely used in scientific computing, numerical analysis, engineering simulations, weather forecasting, aerospace research, high-performance computing (HPC), and supercomputing applications. Organizations developing computational software continue to hire developers with strong Fortran programming skills.

This interview guide covers frequently asked questions on variables, arrays, loops, procedures, modules, derived types, pointers, memory management, file handling, numerical computation, parallel programming, optimization techniques, and modern Fortran features introduced in recent language standards.

Difficulty
Beginner to Advanced
Topics Covered
Modern Fortran & HPC
Examples
Real Coding Examples
Updated
July 2026

Why Learn Fortran?

Fortran continues to play a significant role in scientific computing because of its outstanding numerical performance and compiler optimizations. Thousands of engineering applications, weather models, computational chemistry tools, and research systems are still written in Fortran, making it an important language for developers working in scientific domains.

Learning Fortran also helps programmers understand numerical algorithms, matrix operations, high-performance computing concepts, memory-efficient programming, and optimization techniques used in computational applications. These skills are valuable for both research and enterprise-level scientific software development.

Topics Covered

  • Fortran Basics
  • Variables & Data Types
  • Arrays & Matrices
  • Loops & Control Statements
  • Functions & Subroutines
  • Modules
  • Derived Types
  • Pointers
  • File Handling
  • Numerical Computing
  • Parallel Programming
  • Performance Optimization
Beginner
1. What is Fortran?
Fortran (Formula Translation) is one of the oldest high-level programming languages, mainly used for scientific and numerical computing.
Beginner
2. Who developed Fortran?
Fortran was developed by John Backus and his team at IBM in the 1950s.
Beginner
3. What is Fortran mainly used for?
It is mainly used in scientific computing, engineering simulations, and high-performance numerical calculations.
Beginner
4. What are basic data types in Fortran?
INTEGER, REAL, DOUBLE PRECISION, COMPLEX, CHARACTER, LOGICAL.
Beginner
5. What is a program structure in Fortran?
A basic program starts with PROGRAM, followed by declarations, executable statements, and ends with END PROGRAM.
Beginner
6. What is IMPLICIT NONE?
It forces explicit declaration of all variables, preventing accidental variable creation.
Beginner
7. What is a variable declaration example?
INTEGER :: a
Beginner
8. What is PRINT statement?
Used to display output on the screen.PRINT *, "Hello"
Beginner
9. What is READ statement?
Used to take input from user.READ *, a
Beginner
10. What is an array in Fortran?
A collection of elements of the same type stored in contiguous memory.
Beginner
11. How to declare an array?
INTEGER :: arr(10)
Beginner
12. What is DO loop?
Used for iteration.DO i=1,10
Beginner
13. What is IF statement?
Conditional execution.IF (a>0) THEN
Beginner
14. What is a function in Fortran?
A block of code that returns a value.
Beginner
15. What is a subroutine?
A procedure that performs a task but does not return a value directly.
Intermediate
16. Difference between function and subroutine?
Function returns a value; subroutine does not return directly but modifies arguments.
Intermediate
17. What is MODULE in Fortran?
A program unit that contains variables, functions, and subroutines for reuse.
Intermediate
18. What is USE statement?
Used to access module contents.USE mymodule
Intermediate
19. What is recursion in Fortran?
A function calling itself using the RECURSIVE keyword.
Intermediate
20. What is dynamic allocation?
Allocating memory at runtime using ALLOCATE.
Intermediate
21. Example of ALLOCATE?
ALLOCATE(arr(100))
Intermediate
22. What is DEALLOCATE?
Frees dynamically allocated memory.
Intermediate
23. What is INTENT in subroutine?
Specifies whether argument is IN, OUT, or INOUT.
Intermediate
24. What is derived data type?
Custom data type defined using TYPE.
Intermediate
25. Example of derived type?
Answer here
Intermediate
26. What is array slicing?
Accessing part of array using colon notation like arr(1:5).
Intermediate
27. What is SELECT CASE?
Multi-branch selection statement similar to switch-case.
Intermediate
28. What is PARAMETER?
Defines constant values.INTEGER, PARAMETER :: pi=3
Intermediate
29. What is intrinsic function?
Built-in functions like SQRT(), SIN(), COS().
Intermediate
30. What is file handling in Fortran?
Using OPEN, READ, WRITE, CLOSE statements.
Advanced
31. What is Fortran 90?
Modern version introducing modules, dynamic memory, and array operations.
Advanced
32. What is Fortran 95?
Improved version with better performance and features.
Advanced
33. What is parallel computing in Fortran?
Using MPI or OpenMP for high-performance parallel execution.
Advanced
34. What is OpenMP?
API for multi-threaded parallel programming.
Advanced
35. What is MPI?
Message Passing Interface used for distributed computing.
Advanced
36. What is pointer in Fortran?
Variable that points to another variable using POINTER attribute.
Advanced
37. What is ASSOCIATED function?
Checks if pointer is associated with a target.
Advanced
38. What is PURE procedure?
A function without side effects.
Advanced
39. What is ELEMENTAL procedure?
Procedure applied element-wise to arrays.
Advanced
40. What is high-performance computing (HPC)?
Using supercomputers for large-scale scientific computations.
Coding Round
41. Print Hello World
Answer here
Coding Round
42. Add two numbers
Answer here
Coding Round
43. Factorial program
Answer here
Coding Round
44. Fibonacci series
Logic: Use loop and sum previous two numbers.
Coding Round
45. Check even or odd
IF (MOD(n,2)==0) PRINT *,"Even"
Coding Round
46. Largest in array
Loop through array and compare elements.
Coding Round
47. Reverse a number
Use MOD and integer division inside loop.
Coding Round
48. Swap two numbers
Answer here
Coding Round
49. Dynamic array allocation
Answer here
Coding Round
50. Subroutine example
Answer here

Continue Your Interview Preparation

Along with Fortran, employers often evaluate programming fundamentals, databases, algorithms, operating systems, and modern programming languages. Practicing multiple technologies can significantly improve your technical interview performance.

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Career Opportunities for Fortran Developers

Although Fortran is one of the oldest programming languages, it remains highly valuable in industries that rely on numerical accuracy and high-performance computing. Many scientific organizations continue to maintain large Fortran codebases while also developing modern applications using recent Fortran standards.

Professionals with strong Fortran skills commonly work in aerospace, climate modeling, computational physics, engineering simulations, weather forecasting, defense research, financial modeling, oil and gas, and supercomputing environments where execution speed and numerical precision are critical.

Tips to Crack a Fortran Interview

  • Understand modern Fortran standards (90, 95, 2003, 2008, and 2018).
  • Practice arrays, matrices, and numerical computation problems.
  • Know modules, procedures, interfaces, and derived data types.
  • Understand pointers, allocatable arrays, and memory management.
  • Prepare file handling and formatted/unformatted I/O questions.
  • Study OpenMP, MPI, and parallel programming concepts.
  • Review optimization techniques used in scientific applications.
  • Practice explaining legacy Fortran code and modernization strategies.

About This Interview Guide

InterviewPitch regularly updates this collection of Fortran Interview Questions and Answers based on industry hiring trends, scientific computing practices, and modern Fortran standards. The guide is designed for beginners, experienced developers, researchers, and HPC professionals preparing for technical interviews.

Each question is accompanied by practical explanations to strengthen your understanding of numerical programming, parallel computing, performance optimization, and software development best practices. We recommend combining these interview questions with hands-on coding practice for the best interview preparation.