  We calculate and discuss the chemical evolution of the isotopic silicon
abundances in the interstellar medium at distances and times appropriate to the
birth of the solar system. This has several objectives, some of which are
related to anomalous silicon isotope ratios within presolar grains extracted
from meteorites; namely: (1) What is the relative importance for silicon
isotopic compositions in the bulk ISM of Type II supernovae, Type Ia
supernovae, and AGB stars? (2) Are $^{29}$Si and $^{30}$Si primary or secondary
nucleosynthesis products? (3) In what isotopic direction in a three-isotope
plot do core-collapse supernovae of different mass move the silicon isotopic
composition? (4) Why do present calculations not reproduce the solar ratios for
silicon isotopes, and what does that impose upon studies of anomalous Si
isotopes in meteoritic silicon carbide grains? (5) Are chemical-evolution
features recorded in the anomalous SiC grains? Our answers are formulated on
the basis of the Woosley \& Weaver (1995) supernova yield survey.
Renormalization with the calculated interstellar medium silicon isotopic
composition and solar composition is as an important and recurring concept of
this paper. Possible interpretations of the silicon isotope anomalies measured
in single SiC grains extracted from carbonaceous meteorites are then presented.
The calculations suggest that the temporal evolution of the isotopic silicon
abundances in the interstellar medium may be recorded in these grains.
