An interesting (but obscure) use of shall is in so-called standardese. Quote from the ANSI Style Guide-sheet:


2. Correct use of "shall, "should" and "must", i.e., correct form of requirements and recommendations:

The correct verb form for indicating a requirement is "shall". The correct verb form for indicating a recommendation is "should". Universally accepted "standardese" does not recognize "must". Use "shall" for indicating a mandatory aspect or an aspect on which there is no option.
This may lead to sentences like this one from the DICOM standard:

The Control Character set C0 shall be invoked in CL and the Graphic Character sets G0 and G1 in GL and GR respectively. Only some Control Characters from the C0 set are used in DICOM (see Section
6.1.3), and characters from the C1 set shall not be used.
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