Something is wrong with my program

[Bob John]

I wrote a program to judge a number is prime or not.
"prime" here means a number that can only be divided by itself or one.
When I compiled it by gcc , the error message came up.And I do not very understand the message , so the compiling progress always can't complete.I checked and checked , modified and modified ,but I can't accomplished all the time.
Could you please help me to correct it?
Thank you .
Here is the source code , written in C :

98624
Here is the error message provided by gcc :

98625

[bruce89]

You're not linking to libm. Use -lm in the gcc command line.

In future, post your source and errors as text, not a screenshot.

[jpmelos]

In future, post your source and errors as text, not a screenshot.

Seconded. Makes it easier for us who want to help to just copy and try to compile the code (if the error is in the code). :)

[monkeyking]

It also makes it easier for catching errors if you compile with -Wall .
You wouldn't have caught this one though...

[Bob John]

Thanks , everyone .

Later I will put all the code in text type.

These two days, I was too busy to log in our ubuntu forum.

Source code text format will come soon ...

[Bob John]

Thanks Everyone！My problem is solved now.

It is right to link to libm.a or type -lm in the gcc command line.

Thank you everyone ! These useful reply were thanked just before. ^_^