beginner in Fortran77

[aaloui]

Hi,

i just started learning Fortran 77 language, (i have already some programming knowledge in C and Pascal but i need to learn fortran 77 for use in other programm which is based on this language). So i started learning it using a book called "Fortran 77 and numerical methods by C Xavier". There i wanted to test some simple programs, for example this programm for calculating triangle area:

C Program for area of triangle


write(*,1)
1 format(1X,'type the sides A, B, C')
read(*,2) A, B, C
2 format(3F10.3)
S=(A+B+C)/2
Area=SQRT(S*(S-A)*(S-B)*(S-C))
write(*,3) Area
3 Format(1X,'Area=',F10.3)
STOP
END

so the problem when i run the programm is that only the first variable is read "wihtout waiting that i give the second and third variables" and area is directly given as "Area= NaN" some, no error is given while
running, i tried 2 compilers (Intel and Force 2.0.9) with same results. When i modify the format to format(F10.3,F10.3,F10.3) its also not working. What i could do is to read the 3 variables in differents read statements and the program will be like this:


C Program for area of triangle


write(*,1)
1 format(1X,'type the sides A, B, C')
read(*,2) A
2 format(F10.3)
read(*,3) B
3 format(F10.3)
read(*,4) C
4 format(F10.3)
S=(A+B+C)/2
Area=SQRT(S*(S-A)*(S-B)*(S-C))
write(*,5) Area
5 Format(1X,'Area=',F10.3)
PAUSE
STOP
END

In this case its working, so something seems to be wrong in my read and format statement of the 3 variable, i gave exactly the same what is given in the book im using, and there many other programs have read statements in the same manner, so i dont know what im doing wrong or missing. Im very thankful for your support !

Regards.
Ali.

 

[IRstuff]

How are you entering the inputs? Do you understand what you specified in the format statement for the input? F10.3 means that you;re allocating 10 characters in the input stream for a single floating point value with 3 decimal places. That means that the second input cannot be anywhere but in the next 10 characters.

TTFN
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[xwb]

Might be better if you picked up a more modern version of Fortran like 95, 2003 or even 2008. You don't have the problems of fixed formatting and you have dynamic arrays and type definitions which will help you a lot more.

Re your problem: read as * instead of specifying a format: that way it is free format input. Might be an idea to print the values after you have read them to see what you have read.

 

[aaloui]

Hi,

first i thank ev. body for support. I found out the problem, when i put format(3F10.3) which is equivalent to put format(F10.3,F10.3,F10.3) then the 3 variables have to be input in the same form as the Format so
A,B,C together and then i have to press enter, when i put Format(F10.3) then i can put the 3 variables after each other as i was trying to do..ok it can be seen evident, but as i said im new in this language..

Concerning xwb´s comment, thank you for recommending newer versions of fortran, i believe many things have been inproved and new things added there, but as i wrote i have other other software(s) based on Fortran77 and old codes as well, that i need to understand them as they are, if i were experienced in Fortran amy be it would be the same for me..

Thanks ev. body,

Ali.

 

[DanTex]

Note that Fortran 90 onward is backward compatible with Fortran 77 (only a very few minor exceptions). So... you can read/write F77 with a newer version compiler. And, the newer compilers are much more likely to find "bugs" in some of your older codes.

Dan