Your first program

program unit

A standalone Fortran program starts with the program statement, contains declarations and actions, and ends with end program.

The second line, implicit none, turns off old automatic typing and forces every name to be declared. Always include it.

program hello implicit none print *, "Hello, Fortran" end program hello

Save this text as hello.f90. The .f90 ending means free form source, which is the only style used in this course.

print to screen

The print statement with an asterisk writes to the screen with default formatting, which is perfect for learning.

Text goes in double quotes, numbers and variables follow the comma, and each print starts a new line.

program demo implicit none print *, "2 + 3 =", 2 + 3 end program demo

Compile it

Compile the saved file with gfortran and run the created binary.

gfortran -Wall -Wextra -std=f2018 hello.f90 -o hello

./hello

Hello, Fortran

Warning flags do not change the program. They only ask the compiler to report suspicious code before it builds the binary.

Common beginner mistakes

Most first errors come from three habits: a missing implicit none, a missing end program line, or single quotes around text.

Use double quotes for strings, close every program unit, and keep implicit none as the first line inside the unit.

When the compiler reports a line number, open the file at that exact line first. The cause is usually a missing comma or a misspelled name right above it.

program careful implicit none integer :: year year = 2026 print *, "Year =", year end program careful

Next: Program structure

Article author: Arthur Isaev