  These lecture notes are based on a course on string theories given by Hirosi
Ooguri in the first week of TASI 96 Summer School at Boulder, Colorado. It is
an introductory course designed to provide students with minimum knowledge
before they attend more advanced courses on non-perturbative aspects of string
theories in the School. The course consists of five lectures: 1. Bosonic
String, 2. Toroidal Compactifications, 3. Superstrings, 4. Heterotic Strings,
and 5. Orbifold Compactifications.
