If you're using 64-bit processor - which nowadays is quite common - you can compile 4th as 64-bit compiler. To do this, just delete patch #02 before compilation. But read the following excerpt from original 4th docs first: 25.7 64-bit platforms Although 4tH will work perfectly well on a 64-bit platform there are some disadvantages: • HX files generated by this compiler are not portable to 32-bit platforms • Some 4tH library files may not work properly without some modifications. A quick fix is to change the size of a cell to a four byte datatype. The following procedure will usually work. Open 4th.h and change these lines: #define CELL_MIN LONG_MIN #define CELL_MAX LONG_MAX typedef long cell; To this: #define CELL_MIN INT_MIN #define CELL_MAX INT_MAX typedef int cell; Save 4th.h and compile as described in the previous sections. If you want a full 64-bit 4tH compiler, be aware that: • You cannot compile 4tH as a shared library • You have to regenerate the include files manually, unless you're working with Linux. Linux automatically recreates the include files each time you perform a compile. If you're working with a GNU toolset, you may try the Linux Makefile. If that doesn't work or isn't an option in your particular situation you'll have to perform the procedure listed in section [sec:Regenerating-the-include].