Question: I am new in Linux, can anyone tell me which directory the computer search for "ansinist.h"? Below is the syntax:

```
USER@USER-PC /cygdrive/f/Dataset_extract/500ppi-Legacy/SRC/BIN/TXT2NIST
$ make -f makefile.mak
gcc -ansi -O2  -I/include -L/lib -c txt2nist.c
txt2nist.c:15:22: fatal error: ansinist.h: No such file or directory
 #include <ansinist.h>
                      ^
compilation terminated.
makefile.mak:53: recipe for target 'txt2nist.o' failed
make: *** [txt2nist.o] Error 1

```

Answer: 
[This answer](https://askubuntu.com/questions/395490/gcc-cannot-find-ansinist-h-even-though-it-is-there-in-usr-incude-ansinist) could help you. In general case, be sure that you have installed the libraries that you're going to use in your project.
1)if your header file is in current directory then use #include "ansinist.h"
because this syntax search directly into current directory.

2)if your header file is in /usr/include/ then #include< ansinist.h>
because this syntax first search into /usr/include/ then current directory.

3)also you can use #include < /path/ansinist.h>
where path=path where is header file.

4)if above things will not work then please give value of #echo $PATH for next i can help you.