An entire Fortran program can pass control to a subsequent phase, exiting to the Supervisor with an instruction to load the follow-on phase into core memory. A large program might be split into three parts, separately compiled, called PART1, PART2, and PART3. Execution is started by codice_27 and at a suitable point, PART1 would execute the Fortran statement codice_28 and so forth. The name of the successor program in the CALL can not be variable, but program logic can govern whether control is transferred to another phase, and which codice_29 statement is executed. As mentioned above, the Fortran compiler itself was written this way, with each phase of compilation achieved by a separate program.