#### 2.6.1 Environment Variables for the Microcode

These environment variables are referred to by the microcode: the executable C program called `mit-scheme-ARCH-VERSION`. The values they specify are overridden by the corresponding command-line options, if given.

`MITSCHEME_BAND` ¶

  The initial band to be loaded. The default value is `all.com`.

`MITSCHEME_LIBRARY_PATH` ¶

  A list of directories. These directories are searched, left to right, to find bands and various other files. On unix systems the list is colon-separated, with the default `/usr/local/lib/mit-scheme-ARCH-VERSION`.

`MITSCHEME_CONSTANT` ¶

  The size of constant space, in 1024-word blocks; overridden by `--constant`. The default value is computed to be the correct size for the band being loaded.

`MITSCHEME_HEAP_SIZE` ¶

  The size of the heap, in 1024-word blocks; overridden by `--heap`. The default value depends on the architecture: for 32-bit machines the default is ‘`3072`’, and for 64-bit machines the default is ‘`16384`’.

`MITSCHEME_STACK_SIZE` ¶

  The size of the stack, in 1024-word blocks; overridden by `--stack`. The default value is ‘`1024`’.