The implicit none statement is a non-executable statement
The implicit none statement is used to inhibit a very old feature of Fortran that by default treats all variables that start with the letters i, j, k, l, m and n as integers and all other variables as real arguments. Implicit None should always be used. It prevents potential confusion in variable types, and makes detection of typographic errors easier.
This is how the implicit none statement should be used:
program new implicit none
Notice that the implicit none statement comes right after the program statement. The only statement that is permitted between the program statement and the implicit statement is the USE statement. Remember, following the implicit none statement will be your variable declarations.
lecture five , 18
examples secant.f and sums.f
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