How to run LEX and YACC program in window 7

1) flex-2.5.4a-1.exe

2) bison-2.4.1-setup.exe

3) After that, do a full install in a directory of your preference without spaces in the name. I suggest       C:\GnuWin32. Do not install it in the default (C:\Program Files (x86)\GnuWin32) because bison has problems with spaces in directory names, not to say parenthesis.

4) Also, consider installing Dev-CPP in the default directory (C:\Dev-Cpp)

5) After that, set the PATH variable to include the bin directories of gcc (in C:\Dev-Cpp\bin) and flex\bison (in C:\GnuWin32\bin). To do that, copy this: ;C:\Dev-Cpp\bin;C:\GnuWin32\bin and append it to the end of the PATH variable, defined in the place show by this figure:

6) Open a prompt, cd to the directory where your ".l" and ".y" are, and compile them with:

1. flex hello.l 
2. bison -dy hello.y 
3. gcc lex.yy.c y.tab.c -o hello.exe