## 5.1 Deviations from the standard

[2] Identifiers are by default case-sensitive.

[4.1.6] `set!` for unbound toplevel variables is allowed.

[6.2.4] The runtime system uses the numerical string-conversion routines of the underlying C library and so does only understand standard (C-library) syntax for floating-point constants.

[6.2.5] The routines `complex?`, `real?` and `rational?` are identical to the standard procedure `number?`. The procedures `numerator`, `denominator` and `rationalize` are not implemented. Also not implemented are all procedures related to complex numbers.

[6.2.6] The procedure `string->number` does not obey read/write invariance on inexact numbers.

[6.5] Code evaluated in `scheme-report-environment` or `null-environment` still sees non-standard syntax unless running under the interpreter (`csi`) invoked with the `-strict` option.

[6.6.2] The procedure `char-ready?` is handling terminal input ports only under DJGPP correctly. On other platforms it returns always `#t`. The procedure `read` does not obey read/write invariance on inexact numbers.

[6.6.3] The procedures `write` and `display` do not obey read/write invariance to inexact numbers.