In 1973, Version 4 Unix was rewritten in the higher-level language C, contrary to the general notion at the time that an operating system's complexity and sophistication required it to be written in assembly language. The C language appeared as part of Version 2. Thompson and Ritchie were so influential on early Unix that McIlroy estimated that they wrote and debugged about 100,000 lines of code that year, stating that "names may safely be assumed to be attached to almost everything not otherwise attributed". Although assembly did not disappear from the man pages until Version 8, the migration to C suggested portability of the software, requiring only a relatively small amount of machine-dependent code to be replaced when porting Unix to other computing platforms. Version 4 Unix, however, still had considerable PDP-11-dependent code and was not suitable for porting. The first port to other platform was made five years later (1978) for Interdata 8/32.