Fortran - Programming Style

Programming style is all about following some rules while developing programs. These good practices impart values like readability, and unambiguity into your program.
A good program should have the following characteristics:

• Readability
• Proper logical structure
• Self-explanatory notes and comments

For example, if you make a comment like the following, it will not be of much help:

! loop from 1 to 10 
do i=1,10  

However, if you are calculating binomial coefficient, and need this loop for nCr then a comment like this will be helpful:

! loop to calculate nCr 
do i=1,10

• Indented code blocks to make various levels of code clear.
• Self-checking codes to ensure there will be no numerical errors like division by zero, square root of a negative real number or logarithm of a negative real number.
• Including codes that ensure variables do not take illegal or out of range values, i.e., input validation.
• Not putting checks where it would be unnecessary and slows down the execution. For example:

real :: x 
x = sin(y) + 1.0

if (x >= 0.0) then
   z = sqrt(x)
end if

• Clearly written code using appropriate algorithms.
• Splitting the long expressions using the continuation marker ‘&’.
• Making meaningful variable names.